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Interference in Implanted Cardiac Devices, Part II
... In Bezug auf die Kompatibilität in der medizinischen Bildgebung wurde in dieser Arbeit auch die Beeinflussung von medizinischen Implantaten durch ionisierende Strahlung untersucht. Herzschrittmacher, Kardioverter-Defibrillatoren oder andere aktive medizinische Implantate können in ihrer Funktion durch ionisierende Strahlung, die bei verschiedenen diagnostischen und therapeutischen Anwendungen appliziert wird, beeinträchtigt werden (28,97,111). In dieser Studie wurden verschiedene elektronische Bauteile, wie Kondensatoren, Transistoren, Batterien und Speicherkarten in einer gewebeäquivalenten Messumgebung bestrahlt und dabei auf ihre Funktionalität überprüft. ...
... According to the compatibility in medical imaging, the influence of ionizing radiation on medical implants was also examined in this study. Pacemakers, cardioverter-defibrillators or other active medical implants may be impaired in their function by ionizing radiation which is applied in various diagnostic and therapeutic applications (28,97,111). In this work, various electronic components such as capacitors, transistors, batteries and memory cards were irradiated in a tissue-equivalent measurement environment and their functionality was analyzed. ...
Diese Arbeit beschäftigt sich mit der Kompatibilität in der medizinischen Bildgebung unter zwei verschiedenen Aspekten: (A) Beeinflussung von Gradientenfeldern durch das Magnetsystem eines Magnetresonanztomographen. (B) Beeinflussung elektronischer Bauteile durch ionisierende Strahlung. Imperfektionen in der Gradientenhardware (7–13) führen dazu, dass nicht die ideale zeitliche Gradientenform ausgespielt wird, sondern eine verzerrte Version der Gradienten (6,14). In der nicht-kartesischen Bildgebung führen diese resultierenden Abweichungen in den k-Raum Trajektorien zu Bildartefakten, die sich negativ auf die Diagnosestellung auswirken können. Die linearen und zeitinvarianten Eigenschaften des Gradientensystems ermöglichen die Bestimmung der Übertragungsfunktion (GSTF) (20). Diese Übertragungsfunktion kann innerhalb der Bildrekonstruktion zur Trajektorienkorrektur verwendet werden (14,15,70). In dieser Arbeit wurden mit der Feldkamera (Skope Magnetic Resonance Technologies, Zürich, Schweiz) (22,23) und der schichtselektiven Phantommethode (5,6) zwei etablierte GSTF-Messverfahren verglichen. Dabei wurde die Notwendigkeit einer Abtastzeitkompensation festgestellt, um die GSTF-Informationen entsprechend der gewählten Abtastzeit zu korrigieren (s. Abbildung 16) und die Trajektorien hinreichend zu korrigieren und damit Bildartefakte zu reduzieren. Die Langzeit- und Temperaturanalyse der GSTF zeigte für zwei verschiedene Siemens-Tomographen (Siemens Healthcare, Erlangen, Germany) eine Langzeit und Temperaturstabilität, auch bei extensiven Duty-Cyclen. Damit lässt sich auch einfach eine Pre-emphasis-Korrektur der Gradienten realisieren, was exemplarisch mit einer Zig-Zag- und einer Spiral-Sequenz gezeigt werden konnte. Die GSTF-Pre-emphasis-Korrektur lieferte dabei ähnliche Ergebnisse wie die GSTF-Post-Processing-Technik (s. Abbildung 44 und 47). In Bezug auf die Kompatibilität in der medizinischen Bildgebung wurde in dieser Arbeit auch die Beeinflussung von medizinischen Implantaten durch ionisierende Strahlung untersucht. Herzschrittmacher, Kardioverter-Defibrillatoren oder andere aktive medizini- sche Implantate können in ihrer Funktion durch ionisierende Strahlung, die bei verschiedenen diagnostischen und therapeutischen Anwendungen appliziert wird, beeinträchtigt werden (28,97,111). In dieser Studie wurden verschiedene elektronische Bauteile, wie Kondensatoren, Transistoren, Batterien und Speicherkarten in einer gewebeäquivalenten Messumgebung bestrahlt und dabei auf ihre Funktionalität überprüft. Die Messumgebung simuliert dabei die Wechselwirkungseigenschaften von menschlichem Gewebe mit ionisierender Strahlung in einem Energiebereich von 10 keV – 6 MeV. Zudem ermöglicht sie mit der Einschubeinheit die Integration von Implantaten/elektronischen Bauteilen, sowie eine realistische Bestrahlungsplanung und Dosisverifikation (35,77). Bei den Kondensatoren zeigten sich während der Bestrahlung ein verändertes Funktionsverhalten, mit signifikant abweichenden Spannungen und Zeitkonstanten gegenüber dem unbestrahlten Zustand. Auch die Batterien haben sich während der Bestrahlung signifikant schneller entladen, als ohne Strahlungsapplikation. Nach der Bestrahlung konnten bei den untersuchten SD-Speicherkarten auch Veränderungen in den Speicherzellen festgestellt werden. Bei den Transistoren war aufgrund von Fehlern im Messsetup und dem Schaltungsdesign keine genauere teststatistische Auswertung möglich. Zusammenfassend lässt sich sagen, dass sich charakteristische Kenngrößen der untersuchten Bauteile bei Strahlungsapplikation signifikant veränderten.
... 4,5 On the other hand, some hazardous factors may still be present in the hospital environment, such as radiotherapy (RT) of cancer patients. 6 Due to the risk of device malfunction, the ability to predict and reduce these negative effects plays a central role for safe treatment of PM/ICD patients in these circumstances. ...
... 22,24,79 Also, all shielding of the device should originate from the LINAC rather than from additional shielding with lead. 9,23,79 Although it has previously been recommended to shield the device with a lead alloy during RT in order to keep the dose as low as possible, 6,9,81,83,84 this would only have a limited effect due to scatter within the patient if the device is outside the RT field. 9 In case of direct radiation, a simple lead apron would also be ineffective, as 90% attenuation of 6 MV photon beam can only be achieved by .5 cm thick lead shield. ...
An increasing number of patients with implantable cardiac rhythm devices undergo radiotherapy (RT) for cancer and are thereby exposed to the risk of device failure. Current safety recommendations seem to have limitations by not accounting for the risk of pacemakers and implantable cardioverter defibrillators malfunctioning at low radiation doses. Besides scant knowledge about optimal safety measures, only little is known about the exact prevalence of patients with devices undergoing RT. In this review, we provide a short overview of the principles of RT and present the current evidence on the predictors and mechanisms of device malfunctions during RT. We also summarize practical recommendations from recent publications and from the industry. Strongly associated with beam energy of photon RT, device malfunctions occur at ∼3% of RT courses, posing a substantial issue in clinical practice. Malfunctions described in the literature typically consist of transient software disturbances and only seldom manifest as a permanent damage of the device. Through close cooperation between cardiologists and oncologists, a tailored individualized approach might be necessary in this patient group in waiting time for updated international guidelines in the field.
Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.
... The suggested guidelines for reprogramming a CIED or applying a magnet in various clinical 6 situations are listed in Table 4. In cases of detectable inhibition of a PPM or evidence indicating that ICD shock therapy is being 9 delivered, the surgeon should be informed immediately, and the use of equipment capable of 10 producing EMI should be intermittent (breaks of 5 s between use) for short bursts (< 5 s) or 11 discontinued [37]. The application of a magnet can also be considered. ...
The use of cardiac implantable electronic devices (CIEDs) has increased significantly in recent years. Consequently, more patients with CIEDs will undergo surgery during their lifetime, and thus the involvement of anesthesiologists in the perioperative management of CIEDs is increasing. With ongoing advancements in technology, many types of CIEDs have been developed, including permanent pacemakers, leadless pacemakers, implantable cardioverter defibrillators, cardiac resynchronization therapy-pacemakers/defibrillators, and implantable loop recorders. The functioning of CIEDs exposed to an electromagnetic field can be affected by electromagnetic interference, potential sources of which can be found in the operating room. Thus, to prevent potential adverse events caused by electromagnetic interference in the operating room, anesthesiologists must have knowledge of CIEDs and be able to identify each type. This review focuses on the perioperative management of patients with CIEDs, including indications for CIED implantation to determine the baseline cardiovascular status of patients; concerns associated with CIEDs before and during surgery; perioperative management of CIEDs, including magnet application and device reprogramming; and additional perioperative provisions for patients with CIEDs. As issues such as variations in programming capabilities and responses to magnet application according to device can be challenging, this review provides essential information for the safe perioperative management of patients with CIEDs.
... These conditions include parameters such as: region of battery depletion and pacing failure, circuit damage, threshold elevation, and triggering of inappropriate therapy (shocks) in the case of ICDs. 605 To minimize the risks of using electrocautery, some precautions should be taken perioperatively: (1) the monopolar probe should be used intermittently, with short bursts of current and low energy levels; (2) the indifferent plate should be positioned so that the current does not flow through the generator or electrodes. ...
... A eletrocirurgia monopolar pode provocar várias anormalidades nos DCEI, tais como reprogramação do gerador de pulsos, inibição temporária da estimulação, deflagração de estimulação em frequência elevada, depleção da bateria e falha de estimulação, dano ao circuito, aumento de limiares, e disparo de terapia inapropriada (choques) em caso de CDI. 605 Para minimizar os riscos do uso do eletrocautério, alguns cuidados devem ser tomados no perioperatório: (1) a aplicação do bisturi monopolar deve ser intermitente, em pulsos de curta duração e com menor energia; (2) a placa indiferente deve ser posicionada em local de modo que a energia não flua através do gerador ou eletrodos. ...
... Magnetic guided delivery may be a solution, as suggested by Zhang et al. [49]. However, in a clinical setting, there would be a significant risk of magnetic interference in patients with heart devices [51]; therefore, this strategy may be applied only in selected cases. In the vast majority of the studies, the local delivery of VEGF proved significantly increased capillary density, suggestive for angiogenesis. ...
Cardiovascular diseases are the main cause of death worldwide, a trend that will continue to grow over the next decade. The heart consists of a complex cellular network based mainly on cardiomyocytes, but also on endothelial cells, smooth muscle cells, fibroblasts, and pericytes, which closely communicate through paracrine factors and direct contact. These interactions serve as valuable targets in understanding the phenomenon of heart remodeling and regeneration. The advances in nanomedicine in the controlled delivery of active pharmacological agents are remarkable and may provide substantial contribution to the treatment of heart diseases. This review aims to summarize the main mechanisms involved in cardiac remodeling and regeneration and how they have been applied in nanomedicine.
... EGMs related to myopotentials are noted on the lead spatially closer to the muscles (e.g. diaphragmatic e right ventricular lead, pectoral e unipolar leads), can be reproduced by specific maneuvers, and have high frequency with low amplitude [4]. EGM's due to LD are noted in the specific lead channels, especially in the case of a bipolar lead. ...
Pacemaker-troubleshooting is an important step in the evaluation of a patient with syncope post-pacemaker-implantation. The basic functions of sensing, pacing, and impedance may remain spuriously normal in the case of lead-microfracture or insulation break. We report a case in which the lead dysfunction was diagnosed based on multiple episodes of premature ventricular beats.
... 6,7 Advice has been disseminated to patients to evade magnetic resonance imaging machines, cell phones and electrocautery devices. [8][9][10] The dental literature also comprises of articles that counsel practitioners to avoid operating certain dental devices as they may produce electromagnetic interference and cause pacemakers to not function properly. [10][11][12][13][14][15][16][17][18][19][20] Indication, is that electromagnetic interference of the activity of newer advanced-design pacemakers and ICDs during the operation of select electronic dental devices may be less of a concern. ...
Aim: The purpose of our research was to evaluate the effects of dental electromagnetic devices on the functioning of implanted cardiac devices in patients. Methodology: Biotronik Actros DR+ pacemaker was evaluated at maximum sensitivity on a flat bench top. The pacemaker lead, electronic apex locator, and oscilloscope were connected across a 150-ohm resistor. Pace monitoring was carried out with a Biotronik EPR 1000 programmer and a Tektronix TDS 220 2-channel digital real-time oscilloscope. Results: Four of five electronic apex locators tested did not cause inhibition or interfere with normal pacemaker function. Conclusion: It seems that electronic apex locators can be used safely in patients with pacemakers.
... frequency ablation, and electroconvulsive therapy. In the nonmedical environment, potential sources of EMI include suboptimally shielded electrical mains supplies and electrical equipment, mobile phones, electronic article surveillance gates, and magnets(18).The TASER device used in this case report delivers electrical energy at 19 Hz, which is also well within the cardiac signal range. This makes it difficult to incorporate strategies such as bandpass and notch filtering to reduce the risk of EMI being sensed inappropriately by the device. ...
... Th e magnet application excludes this option in the case of pacemakers, whereas ICDs (produced by Sorin and Boston Scientifi c) need to be reprogrammed. 4. Type of cautery used in surgery Electromagnetic interference is more frequent when using unipolar electrocautery, so the use of bipolar electrocutters is preferred for these patients. ...
Four thousand cardiac implantable electronic devices (CIED) are implanted yearly in Croatia with constant increase. General anesthesia and surgery carry some specific risk for the patients with implanted CIEDs. Since most of the surgical procedures are performed in institutions without reprogramming devices available, or in the periods when they are unavailable, these guidelines aim to standardize the protocol for perioperative management of these patients. With this protocol, most of the procedures can be performed easily and, more importantly, safely in the majority of surgical patients.
... • Radiation based treatment or exams in hospitals: in such case, the patient is exposed to high-density external radiations. Several accounts of deaths in pacemaker patients due to Magnetic Resonance Imaging (MRI) were reported by the Food and Drug Administration (FDA) [3]. Another example of a hostile environment in hospitals is the radiotherapy treatment of cancer [4]. ...
Progressive shrinking of CMOS device sizes has permitted reductions in power consumption and miniaturization of electronic devices. In parallel, modern pacemakers implemented with advanced technologies have proved to be more sensitive than earlier models to soft-errors induced notably by external radiations. Traditionally, the analysis of the impact of soft-faults, like those induced by Single Event Upsets (SEUs), on the behavior of pacemaker devices, has been carried out by dynamic radiation ground testing and clinical observations. However, these techniques are expensive. They can only be done very late in the design cycle, after the design is manufactured and in part after it is implanted. This paper presents a new model-based analysis of the impact of Soft-Faults (SFs) on the behavior of cardiac pacemakers at systemlevel. It is performed by: 1) introducing a new Probabilistic Timed Automata (PTA) model; 2) verifying this model against a set of functional properties to ensure it meets its specifications under normal conditions; 3) applying a new methodology to inject SFs at a certain time in the PTA model of the pacemaker and to verify their impact on the pacemaker’s behavior is introduced; and 4) identifying different scenarios for Soft-Faults (SFs) that may lead to malfunction including Oversensing, Undersensing, and Output Failure. The reported formal modeling is done in PRISM and the analysis is done with the Storm model checker.
... MRI has now become the image modality of choice for imaging the brain, spine, musculoskeletal system, head and neck, and other tissue structures for the previous features [6]. MR scanners use a high-strength static magnetic field as well as powerful radiofrequency and gradient magnetic fields to produce images [7][8]. In the early 1990s, the first MRI researchers collected the data. ...
... MRI has now become the image modality of choice for imaging the brain, spine, musculoskeletal system, head and neck, and other tissue structures for the previous features [6]. MR scanners use a high-strength static magnetic field as well as powerful radiofrequency and gradient magnetic fields to produce images [7][8]. In the early 1990s, the first MRI researchers collected the data. ...
OBJECTIVE. Many studies testing the use of pacemakers with Magnetic resonance imaging (MRI) have been done. Some articles encourage performing the MRI test and others prefer to be in safe side. My aim was to summarize these studies to figure out the safety of MRI for patients with cardiac pacemakers. I made a systematic search of peer-reviewed databases. A total of 12 articles were reviewed.
CONCLUSION. The data are disarray about MRI being considered for patients with pacemakers, and for the benefits of the imaging should ignore the risks.
... However, improvements in noise detection, device filtering, and universal use of bipolar leads in current generation CIEDs make this risk very low. 1,2 Several studies have been conducted demonstrating that EMI is unlikely in procedures where monopolar electrosurgery is used distant from the device. [3][4][5][6][7][8][9][10] In 2011, the Heart Rhythm Society/American Society of Anesthesiologists (HRS/ASA) published an Expert Consensus Statement on the Perioperative Management of CIEDs. ...
Background:
There is significant variability in the perioperative management of patients with cardiac implanted electronic devices (CIEDs) undergoing procedures requiring electrosurgery.
Methods:
We performed a multicenter registry from February 2014 to August 2015 at three suburban Chicago hospitals. Patients with transvenous CIEDs undergoing procedures requiring electrosurgery were assigned to one of three groups: (1) Reprogram, (2) Magnet, or (3) No Change. Subjects with ICDs or those pacemaker dependent having surgical procedures within 6 inches of their CIED were assigned to the Reprogram group, whereby ICD therapies were programmed off with asynchronous pacing if pacemaker dependent. Subjects with ICDs ≥ 6 inches from their surgical site but above the iliac crest were assigned to the Magnet group. All others were in the No Change group. We evaluated electromagnetic interference (EMI) and postoperative device reset based on surgical location.
Results:
All patients (n = 331) had pectoral CIEDs with mean age 73 years, 65% male, EF 56% for pacemaker subjects, 35% for ICD subjects with 22% pacemaker dependent. Assignments were n = 52 (16%) Reprogram group, n = 51 (15%) Magnet group and n = 228 (69%) no change. There was EMI in 45% of thoracic cases, 35% of head/neck, 15% of upper extremity and 3% of abdominal cases above iliac crest. There was no EMI in procedures below the iliac crest. There was no inappropriate therapies or device reset.
Conclusion:
Results of the ICD-ON Protocol demonstrate safe and efficient management of patients with CIEDs based on electrosurgery location, with 69% requiring no reprogramming or magnet application. This article is protected by copyright. All rights reserved.
... Electromagnetic interference occurs when the electromagnetic field of an electromagnet, or the flow of electricity generated by an instrument, affects the normal working of a nearby appliance. If electromagnetic signals affect CIEDs, they can produce electrical noise or even simulate the electrical activity of the heart (1)(2)(3)(4)(5). ...
Patients with cardiac implantable electrical devices should take special precautions when exposed to electromagnetic fields. Proximity to equipment used in clinical dentistry may cause interference. This study evaluated in vitro the risks associated with different types/makes of cardiac devices and types of dental equipment. Six electronic dental tools were tested on three implantable cardioverter defibrillators and three pacemakers made by different manufacturers. Overall, the risk of interference with the pacemakers was 37% lower than with the implantable cardioverter defibrillators. Regarding the types/makes of cardiac devices analysed, that from Boston Scientific had a five-fold greater risk of interference than did that from Biotronik [prevalence ratio (PR) = 5.58]; there was no difference between that from Biotronik and that from Medtronic. Among the dental equipment, the electric pulp tester had the greatest risk of inducing interference and therefore this device was used as the benchmark. The electronic apex locator (PR = 0.29), Periotest M (PR = 0.47), and the ultrasonic dental scaler (PR = 0.59) were less likely to induce interference than the electric pulp tester. The risk was lowest with the electronic apex locator. Pacemakers presented a lower risk of light to moderate interference (PR = 0.63). However, the risk of severe electromagnetic interference was 3.5 times higher with pacemakers than with implantable cardioverter defibrillators (PR = 3.47).
... [5,19,20,23,24,30,35] Compared to neurological implantable devices, cardiac implants have well-established guidelines and protocols for perioperative management. [27] The most recent of these, introduced worldwide is a comprehensive presurgical and preprocedural checklist. [38] Implantable cardiac devices It is believed that patients with concomitant implanted cardiac and neurostimulation (NS) devices are at a high risk of interference between these two systems. ...
Background:
Spinal cord stimulation is currently approved to treat chronic intractable pain of the trunk and limbs. However, such implantable electronic devices are vulnerable to external electrical currents and magnetic fields. Within the hospitals and modern operating rooms (ORs), there is an abundance of electrical devices and other types of equipment that could interfere with such devices. Despite the increasing number of patients with neuromodulation implantable devices, there are no written guidelines available or consensus of cautions for such patients undergoing unrelated surgery.
Case descriptions:
A 60-year-old female with a permanent St. Jude's spinal cord stimulator (SCS) presented for open total abdominal hysterectomy. Both the anesthesia and gynecology staffs were aware of the device presence, but were unaware of any precautions regarding intraoperative management. The device was found to be nonmagnetic resonance imaging compatible, and bipolar cautery was used instead of monopolar cautery. A 59-year-old female with a 9-year-old permanent Medtronic SCS, presented for right total hip arthroplasty. The device was switched off prior to entering the OR, bipolar cautery was used, and grounding pads were placed away from her battery site. In each case, the manufacturer's representative was contacted preoperative. Both surgeries proceeded uneventfully.
Conclusions:
The Food and Drug Administration safety information manual warns about the use of diathermy, concomitant implanted stimulation devices, lithotripsy, external defibrillation, radiation therapy, ultrasonic scanning, and high-output ultrasound, all of which can lead to permanent implant damage if not turned off prior to undertaking procedures. Lack of uniform guidelines makes intraoperative management, as well as remote anesthesia care of patients with previously implanted SCSs unsafe.
... Inappropriate shock delivery causes unnecessary pain, anxiety, and depression, besides burdening the health care system with additional costs for emergency room visits, hospitalizations and premature battery depletion. Although a plethora of sources of EMI has been identified [12][13][14][15], publications mostly refer to case reports and data on the incidence of such interferences is limited. Furthermore, the available estimates of EMI incidences are either based on relatively small cohorts or may be outdated [10,16]. ...
Purpose
Electromagnetic interference (EMI) with implantable cardioverter defibrillators (ICDs) can cause oversensing and subsequently inappropriate ICD therapies. We retrospectively investigated the current incidence and clinical relevance of oversensing related EMI in a large cohort of ICD patients.
Methods
From January 2005 to April 2013, all ICD interrogations performed at our institution were analyzed for the occurrence of oversensing related EMI. EMI episodes were classified as clinically significant, potentially significant or of minor significance. To identify risk factors for EMI, we also analyzed different lead models in our cohort (integrated vs true bipolar leads).
Results
Data of 2940 ICD patients (mean age 63 ± 16 years, 2322 male patients, 7772 patient-years) were retrospectively analyzed for the occurrence of EMI. During the observation period, a total of 145 (hospital environment n = 97, non-hospital environment n = 48) episodes occurred and resulted in an overall EMI incidence, i.e. event rate, of 1.87 % per patient per year. Focusing on clinically significant or potentially significant episodes, the EMI incidence was 0.27 % per patient per year. Cox proportional hazards regression analysis did not reveal a statistically significant higher hazard of oversensing for patients with integrated bipolar leads compared to patients with true bipolar leads (HR = 2.21; 95 % CI 0.90–5.39; p = 0.083).
Conclusions
Our data demonstrate that EMI continues to occur in everyday life. Patients should be well informed about the potential sources and risks of EMI but they need not be overly concerned since the risk of EMI—especially in a non-hospital environment—is low.
... The electrosurge is a unipolar or bipolar surgical instrument with cutting and cauterizing functions that employs alternate electrical currents. Within the field of dentistry, the most commonly used electrosurge instrument is unipolar with a low-intensity current and a frequency of 100 KHz (3,16,17). The osseointegration monitoring tools Osstell ISQ and Periotest M are based on differing principles. ...
Patients with cardiac implantable electrical devices should take precautions when exposed to electromagnetic fields. Possible interference as a result of proximity to electromagnets or electricity flow from electronic tools employed in clinical odontology remains controversial. The objective of this study was to examine in vitro the capacity of dental equipment to provoke electromagnetic interference in pacemakers and implantable cardioverter defibrillators. Six electronic dental instruments were tested on three implantable cardioverter defibrillators and three pacemakers from different manufacturers. A simulator model, submerged in physiological saline, with elements that reproduced life-size anatomic structures was used. The instruments were analyzed at differing distances and for different time periods of application. The dental instruments studied displayed significant differences in their capacity to trigger electromagnetic interference. Significant differences in the quantity of registered interference were observed with respect to the variables manufacturer, type of cardiac implant, and application distance but not with the variable time of application. The electronic dental equipment tested at a clinical application distance (20 cm) provoked only slight interference in the pacemakers and implantable cardioverter defibrillators employed, irrespective of manufacturer.
© 2015 Eur J Oral Sci.
... For cardiac imaging, the main problem to solve is metallic artefact, especially on the gradient-echo sequences. 19 Like in research performed by Nazarian et al., 9 several scan protocols were used to see if any yielded different effects or reduced the qualitative extent of artefact. Gradient mode was changed from Normal to Whisper, resulting in slower ramping of the field and therefore diminishing the changes of the magnetic field in time. ...
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Our aim was to evaluate the potential for safely imaging patients with a new type of implantable cardioverter-defibrillator called the subcutaneous implantable cardioverter-defibrillator (S-ICD) in a 1.5 T magnetic resonance imaging (MRI) scanner. With the increasing number of patients with cardiac implantable devices who are indicated for MRI, there is a growing need for establishing MRI compatibility of cardiac implantable devices.
Patients with implanted S-ICD systems underwent one or more types of anatomical MRI scans. The S-ICD was programmed off and patients were monitored throughout the imaging procedure. Device function was evaluated pre- and post-scan. Patients were asked to report immediately any pain, torqueing movement, or heating sensation in the area of the pocket or electrode. Fifteen patients underwent a total of 22 examinations at 1.5 T. Scans included brain, spine, knee, and heart. Two patients were re-scanned due to complaints of heating over the can during lumbar scans, which was caused by a thermistor probe placed on the skin to measure skin temperature. All the remaining scans occurred without incident. No evidence of device malfunction was observed.
This study is the first to domonstrate the feasibility of exposing S-ICD patients to MRI using the scanning and monitoring protocol described. More data are required to support S-ICD as a MRI conditional device.
© The Author 2015. Published by Oxford University Press on behalf of the European Society of Cardiology.
... It is well known that electromagnetic interference can pose a danger to patients with an ICD; 15,16 ventricular oversensing with subsequent delivery of inappropriate therapies, temporary or definitive suspension of all antitachycardia therapies or hardware damage can pose as possible mechanisms. [17][18][19] In other situations the use of magnets is desirable, for example when an ICD needs to be voluntarily inhibited from delivering therapies in surgical patients when tools that can interefere with the ICD are used. Magnets are also employed in emergency situations to terminate therapy delivery in cases of inappropriate arrhythmia detection. ...
To investigate a potential relationship between implantable cardioverter defibrillator (ICD) therapies and daily geomagnetic activity (GMA) recorded in a large database.
The ALTITUDE database, derived from the Boston Scientific LATITUDE remote monitoring system, was retrospectively analyzed for the frequency of ICD therapies. Daily GMA was expressed as the planetary K-index and the integrated A-index and was graded as levels I (quiet), II (unsettled), III (active), and IV (storm).
A daily mean ± SD of 59,468±11,397 patients were monitored between January 1, 2009, and May 15, 2012. The distribution of days according to GMA was as follows: level I, 924/1231 (75%); level II, 226/1231 (18%); level III, 60/1231 (5%); and level IV, 21/1231 (2%). The daily mean ± SD numbers of ICD shocks received per 1000 active patients in the database were 1.29±0.47, 1.17±0.46, 1.03±0.37, and 0.94±0.29 on level I, II, III, and IV days, respectively; the daily mean ± SD sums of shocks and antitachycardia pacing therapies were 9.29±2.86, 8.46±2.45, 7.92±1.80, and 7.83±2.28 on quiet, unsettled, active, and storm days, respectively. A significant inverse relationship between GMA and frequency of ICD therapies was identified, with the most pronounced difference between level I and level IV days (P<.001 for shocks; P=.008 for shocks + antitachycardia pacing).
In a large-scale cohort analysis, ICD therapies were delivered less frequently on days of higher GMA, confirming the previous pilot data and suggesting that higher GMA does not pose an increased risk of arrhythmias using ICD therapies as a surrogate marker. Further studies are needed to gain an in-depth understanding of the underlying mechanisms.
Copyright © 2015 Mayo Foundation for Medical Education and Research. Published by Elsevier Inc. All rights reserved.
... In a few case reports, these complications have been documented secondary to cautery use or associated with radiotherapy or radiofrequency ablation procedures, although the risk of these complications is considered quite low due to the incorporation of protective circuitry in modern pacemaker technology. 13 ''Power on reset'' mode-a simple backup pacing mode (typically VVI or VOO)-may be activated by disruption of a pacemaker's volatile electronic memory. 2. Anatomical consequences associated with surgical procedures-pneumothorax with thoracotomy or cardiac surgery: such results have been linked to changes in pacemaker function due to lead dislodgement, an increase in impedance, particularly with unipolar pacing systems, or an increase in the defibrillation threshold. ...
Purpose
There are more than 200,000 Canadians living with permanent pacemakers or implantable defibrillators, many of whom will require surgery or invasive procedures each year. They face potential hazards when undergoing surgery; however, with appropriate planning and education of operating room personnel, adverse device-related outcomes should be rare. This joint position statement from the Canadian Cardiovascular Society (CCS) and the Canadian Anesthesiologists’ Society (CAS) has been developed as an accessible reference for physicians and surgeons, providing an overview of the key issues for the preoperative, intraoperative, and postoperative care of these patients.
Principal findings
The document summarizes the limited published literature in this field, but for most issues, relies heavily on the experience of the cardiologists and anesthesiologists who contributed to this work. This position statement outlines how to obtain information about an individual’s type of pacemaker or implantable defibrillator and its programming. It also stresses the importance of determining if a patient is highly pacemaker-dependent and proposes a simple approach for nonelective evaluation of dependency. Although the document provides a comprehensive list of the intraoperative issues facing these patients, there is a focus on electromagnetic interference resulting from electrocautery and practical guidance is given regarding the characteristics of surgery, electrocautery, pacemakers, and defibrillators which are most likely to lead to interference.
Conclusions
The document stresses the importance of preoperative consultation and planning to minimize complications. It reviews the relative merits of intraoperative magnet use vs reprogramming of devices and gives examples of situations where one or the other approach is preferable.
We describe the case of a 32-year-old man who developed a liver neoplasm due to previous Fontan surgery (FS) for a single ventricle anomaly and situs viscerum inversus. He was admitted to our hospital for suspected hepatocellular carcinoma during an Ultrasound (US) follow up. Computed tomography (CT) showed features of chronic liver disease and 7 cm hepatic nodule with arterial enhancement. Laboratory analyses documented preserved liver function and increased levels of alpha-fetoprotein. Trans-arterial-chemoembolization (TACE) was performed obtaining complete necrosis at 4 weeks of follow up and significant reduction of alpha-fetoprotein. The patient is currently in follow-up, being evaluated for further treatments and/or combined liver-heart transplantation. TACE is a therapeutic option for the treatment of patients with unresectable hepatocellular carcinoma (HCC) and with severe heart disease, like those submitted to FS and with also other vascular abnormalities like those correlated to situs viscerum inversus.
In the context of the increasing spread of cardiac active implantable heart devices (CIEDs) in the population and of the wide diagnostic/therapeutic utility of magnetic resonance (MRI) examinations, the goal of this paper is to provide the experience of the Santa Maria Nuova Hospital of the USL Tuscany Center in Florence and to report an organizational proposal to perform, in the hospital settings, MRI examinations on patients carrying CIED. This report is intended to show the operational choices of a Radiology Department which organizes this activity in accordance with the new Italian regulatory framework in the field of safety of MR sites (Ministero della Salute in Decreto Ministeriale 10 agosto 2018 Determinazione degli standard di sicurezza e impiego per le apparecchiature a risonanza magnetica, 2018).
Recent research has shown that the integrity of sensor measurements can be violated through out-of-band signal injection attacks. These attacks target the conversion process from a physical quantity to an analog property—a process that fundamentally cannot be authenticated. Out-of-band signal injection attacks thus pose previously-unexplored security risks by exploiting hardware imperfections in the sensors themselves, or in their interfaces to microcontrollers. In response to the growing-yet-disjointed literature in the subject, this article presents the first survey of out-of-band signal injection attacks. It focuses on unifying their terminology and identifying commonalities in their causes and effects through a chronological, evolutionary, and thematic taxonomy of attacks. By highlighting cross-influences between different types of out-of-band signal injections, this paper underscores the need for a common language irrespective of the attack method. By placing attack and defense mechanisms in the wider context of their dual counterparts of side-channel leakage and electromagnetic interference, this study identifies common threads and gaps that can help guide and inform future research. Overall, the ever-increasing reliance on sensors embedded in everyday commodity devices necessitates that a stronger focus be placed on improving the security of such systems against out-of-band signal injection attacks.
A detailed and thorough examination of the periodontal tissues is essential to ascertain disease extent and severity in patients with periodontitis. This chapter considers the key aspects of the medical and dental history that are relevant to the management of periodontitis. It describes the clinical factors to assess when deciding which sites require periodontal treatment. It is necessary to perform a complete oral and dental examination. Extraoral assessment should focus on the lymph nodes, temporomandibular joints, and muscles of mastication. Intraoral examination must include a full dental charting (teeth present, caries, restorations, and tooth surface loss) as well as examination of the oral soft tissues (lips, tongue, palate, buccal mucosa, floor of mouth, and oropharynx). The chapter reviews the parameters to be assessed at diseased sites that will influence decisions about how to treat each site. It also considers the medical factors (and other patient factors) that are relevant when planning periodontal therapy.
The subcutaneous implantable cardioverter defibrillator (S-ICD) is a new device used for the prevention of sudden cardiac death. Best practices in the perioperative management of the S-ICD are not established; therefore, clinicians typically deactivate the device during surgery, with reinterrogation and activation postoperatively. This could put the patient at risk for being discharged with the device "off." We present two cases where electromagnetic interference was appropriately detected by the S-ICD and filtered. These cases present an important clinical finding that could lead to less deactivation of devices during surgery. Further research will be required to define which surgical procedures require magnet, reprogramming, or no changes.
We experienced 2 cases in which oversensing of a particular noise after the implantation of an implantable cardiac device was observed in the acute phase. These were unusual cases in which the noise exhibited a low frequency pattern and appeared several hours after the implantation, but disappeared within 1 week. Here we present these cases and the details of an experiment investigating the origin of the noise and the methods for its prevention. The noise in these cases led to pacing inhibition and could have induced an inappropriate shock due to oversensing, but its morphology and electromagnetic interference were atypical for a lead failure or myopotentials. The noise spontaneously disappeared from the analysis of the data stored in the device. In an experiment based on the Irnich model, in which it was assumed that blood invaded a damaged grommet, low frequency noise occurred which was similar to the noise in the two cases. We concluded that care must be exercised when handling grommets.
Tandartsen worden steeds vaker geconfronteerd met patiënten met een pacemaker of implanteerbare cardiale pacemaker. Deze apparaten zijn gevoelig voor elektromagnetische interferentie, die de werking van de pacemaker kan verstoren. Allerlei tandheelkundige apparatuur kan als bron fungeren van lichte of matige elektromagnetische velden. Terughoudendheid bij patiënten met een pacemaker lijkt geboden met het gebruik van magnetostrictieve scalers en ultrasone trilbaden in de nabijheid. Het gebruik van een elektrotoom wordt afgeraden. Andere tandheelkundige elektrische apparatuur lijkt bij moderne pacemakers geen risico op storing te vormen, indien men zich houdt aan het algemene advies om deze alleen te gebruiken op meer dan 15 cm afstand van de pacemaker en de elektroden. Als een tandarts twijfelt of bepaalde apparatuur bij een patiënt gebruikt mag worden, dient voorafgaand overleg met de behandelend cardioloog plaats te vinden.
Advances in cardiac surgery toward the mid-20th century created a need for an artificial means of stimulating the heart muscle. Initially developed as large external devices, technological advances resulted in miniaturization of electronic circuitry and eventually the development of totally implantable devices. These advances continue to date, with the recent introduction of leadless pacemakers. In this first part of a 2-part review, we describe indications, implant-related complications, basic function/programming, common pacemaker-related issues, and remote monitoring, which are relevant to the practicing cardiologist. We provide an overview of magnetic resonance imaging and perioperative management among patients with cardiac pacemakers.
Background:
In the USA, the number of people needing implantable cardioverter defibrillators (ICDs) has grown dramatically. Many ICD recipients will need to undergo a surgical procedure at some point following ICD implantation. Most surgeries involve the use of electrocautery. Currently, the effects of electrocautery-induced electromagnetic interference (EI-EMI) on ICDs are poorly understood. The aim of this study was to study EI-EMI using prospectively collected clinical data.
Methods:
We analyzed prospectively collected ICD data from patients undergoing a surgical procedure at Mayo Clinic between 2011 and 2012. Information on clinical, device history, device interrogation pre- and post-surgery, and surgical information were collected for all patients. ICDs were programmed with detections on and therapies off. The patients were then categorized into two groups: those with EI-EMI inappropriate arrhythmia detection and those without detection. The stored electrograms were reviewed. Clinical and device parameters were analyzed to identify predictors of EI-EMI.
Results:
Of 103 patients studied, bipolar cautery did not induce EI-EMI (0/11 cases), whereas monopolar cautery resulted in noise detection in 11/92 procedures. Among 11 inappropriate episodes of detection, 10 had surgery at chest, neck, and upper extremity sites with cautery current across the ICD lead tip; 1 had abdominal surgery; and none had back or low extremity surgery. On average, the near-field electrogram amplitude values were greater than the far-field amplitude values.
Conclusions:
EI-EMI does not occur when bipolar cautery or monopolar cautery is used below the hips with the dispersive ground pad applied to the lower extremities. In contrast to external EMI, EI-EMI may be larger on near-field than far-field electrograms.
The increasing use of implantable electronic devices such as cardiac pacemakers and neurostimulators means that they are being increasingly encountered in endoscopy departments. The electromagnetic fields generated during electrosurgery and with magnetic imaging systems have the potential to interfere with such devices. The authors present a case that highlights some of the steps necessary for minimising risk, review the evidence and summarise the currently available guidance.
Bradycardia is a common clinical finding, which requires careful and thorough assessment to correctly establish the underlying diagnosis and determine the appropriate therapy. Bradycardia is often a benign condition requiring no intervention, but when it gives rise to symptoms or results from conduction abnormalities that are associated with an adverse prognosis, cardiac pacing may be required unless a reversible and remediable cause can be identified. An accurate electrocardiographic diagnosis, consideration of the clinical context, and confirmation of a temporal association with any symptoms are the essential first steps to determine the appropriate therapy....
Cardiac pacemakers and defibrillators are remarkable devices with the ability to provide marked symptom relief and life-saving therapy. An ever-expanding list of indications continues to enlarge the pool of patients who live with implantable devices. Intrinsic to the function of these devices is the ability to sense intra-cardiac signals. An unfortunate by-product is the potential for electromagnetic energy in the environment to interact with and disturb the normal functioning of these devices. This chapter will review the way electromagnetic interference (EMI) can affect cardiac devices and then discuss specific situations and optimal techniques to minimize the chance of untoward interaction.
This paper presents the design and development of a mini remotely operated vehicle (ROV) system for training purposes at the STRIDE Maritime Technology Division (BTM). The mini ROV is designed for operation in shallow water environments and is capable to dive up to 5.6 m depth. Based on the concept design developed using Solidworks, the buoyancy force and stability required to overcome the total weight of the platform was planned by tuning the locations of the thrusters and electronics compartment. The fabrication processes were divided into several developments including the controller system, thrusters and mainframe. The field test of the mini ROV was conducted successfully in the KD Duyong training pool, with no leakage problems occurring in the electronics compartment. However, manoeuvring difficulties were found at 5 m depth, as the thrusters needed to overcome the surrounding water pressure. This can be overcome using DC motors with the higher rating of motor torque.
Implantable cardioverter-defibrillators (ICDs) are the treatment of choice for most patients who are at high risk for ventricular fibrillation (VF) or life-threatening ventricular tachycardia. Randomized, prospective trials have established that ICDs are superior to antiarrhythmic drugs in survivors of cardiac arrest or hypotensive ventricular tachycardia, 1 and that ICDs provide incremental reduction in total mortality beyond that provided by optimal medical therapy in patients with severe, ischemic cardiomyopathy. 2 Analysis of managed care and Medicare databases 3 indicates that ICD therapy is underutilized based on present guidelines. 4
Background and Objective: As the number of patients with implantable cardiac devices escalates, inadvertent electromagnetic interference (EMI) by electrosurgery carries increasing concern for patient safety. Given the trend for dermatologic care delivery by nonphysician providers, supervising physicians must carefully consider the adequacy of perioperative evaluation in elective or cosmetic settings. Rapidly evolving technology also calls into question potential EMI of new therapeutic modalities (radiofrequency resurfacing, electrochemotherapy, and endovenous ablation). The most recently published recommendations (1998) for care of dermatologic patients with cardiac devices do not differ significantly from guidelines proposed in 1975. These recommendations, based on complications experienced during noncutaneous surgery, are exceedingly conservative and do not take into consideration the different electrosurgical modalities and varying degrees of EMI risk. In addition, modern cardiac devices have evolved significantly with increased sophistication in protection from EMI. A survey of dermatologic surgeons demonstrated low compliance with these existing guidelines. Methods, Results, and Conclusions: Based on a review of the literature and current electrosurgical and cardiac devices, we discuss the potential impact of conventional dermatologic electrosurgery and new technologies. We propose that new perioperative guidelines are needed to provide appropriate safety, facile implementation, and cost-effective care for patients with modern implantable cardiac devices.
Prolonged and excessive exposure to noise inside truck cabins can cause long term harm and adverse effects to drivers. To this end, the objective of this study was to monitor noise exposure at the driver’s ear level while driving a Malaysian Army (MA) three-tonne truck using the Integrated Kurtosis-based Algorithm for Z-notch Filter (I-kazTM) statistical analysis method. The recorded raw noise exposure data was analysed using I-kazTM to provide the I-kazTM coefficient Z∞ and I-kazTM display, which is a 3D graphical representation of the degree of data scattering. It was found that increase of sound pressure level SPL and truck speed result in increase of data scattering in the I-kazTM display and value of Z∞. This study demonstrates that I-kazTM is a very effective method for noise monitoring as it can detect SPL changes that are very small.
The authors aimed to determine whether electrical dental devices would interfere with the function of cardiac pacemakers or implantable cardioverter defibrillators (ICDs) in humans.
The authors exposed asymptomatic nonpacemaker-dependent patients to commonly used electrical dental equipment (for example, battery-operated curing lights, ultrasonic baths, ultrasonic scalers, electric pulp testers, and electric toothbrushes) in an outpatient cardiology clinic. The authors operated dental devices at various distances and programmed cardiac devices to sense and pace. The authors obtained cardiac tracings using a cardiac programming unit and a cardiac provider who noted any interference interpreted the results in real time.
The authors enrolled 32 consecutive patients and tested 12 pacemakers and 20 ICDs. They did not observe any significant clinical interference in sensing and pacing functions in any patient; however, they noted minor interference without clinical impact in the telemetry from the cardiac programming unit during use of the ultrasonic scaler and bath.
The findings of this prospective study suggest that electrical devices commonly used in dental practices do not interfere with the sensing and pacing of contemporary cardiac patients' pacemakers or ICDs. However, they do interfere with the telemetry from the cardiac programming unit, without any clinical impact on patient safety. These findings should help in the development of clinical guidelines regarding dental management of patients with pacemakers or ICDs.
Electrical dental devices (for example, ultrasonic baths, ultrasonic scalers) induced minor interference with programmers that interrogate cardiac devices implanted in patients; however, overall, dental devices do not appear to interfere with pacemakers' and defibrillators' pacing and sensing function.
Copyright © 2015 American Dental Association. Published by Elsevier Inc. All rights reserved.
Wireless spy devices (WSDs) are surveillance equipment, such as listening bugs or cameras, hidden in objects or covertly placed in rooms. Surveillance using WSDs is one of the main methods of recording conversations for both intelligence gathering as well as criminal charges. However, WSDs have also been abused for nefarious purposes, such as industrial espionage and blackmail. This paper is aimed at reviewing WSD technologies, in terms of types, energy sources and modes of operations. Methods used for detecting WSDs, focusing on radio frequency (RF) detectors, spectrum analysis and nonlinear junction detectors (NLJDs), are also be discussed. Keywords: Wireless spy devices (WSDs); active and passive WSDs; radio frequency (RF) detector; spectrum analysis; nonlinear junction detector (NLJD).
Introduction An implanted cardiac pacemaker is usually regarded as a contraindication for magnetic resonance imaging (MRI) due to safety reasons. Nevertheless, at some MRI sites patients with pacemakers underwent MRI examination at different field strengths [1,2]. However, heating of pacemaker leads is still a potentially harmful effect that has drawn recent attention [3,4]. Due to the specific requirements for pacemaker lead design (wires have to be of low resistance, thin, flexible, and unbreakable) the possibilites of design changes are limited. Changes in the winding configuration are among the proposed developments. The aim of this study was to investigate experimentally the heating effects of MRI on old and newer pacemaker leads of varying winding types. The influence of lead positioning and the reproducibility of measurements were analyzed. Methods Heating effects of MRI at 1.5 T (Philips Gyroscan ACS NT) on 9 leads from 3 manufacturers were investigated in vitro. The following categories of lead types were included: unipolar, conventional coaxial bipolar, and coradial bipolar (with both conductors wound into a single coil). The leads were placed inside a 64×33 cm 2 large reservoir filled with 20 l saline water and inserted into the scanner. For maximal power irradiation a turbo-spin echo sequence was used. During the measurements (FOV=400mm, matrix 256x205, TE=20 ms, TR=300 ms, 8 slices, flip angle 90°, turbo factor 6, 4 NEX, scan duration 41 sec, SAR=3.8 W/kg) temperature changes at the tip of the different leads were continuously measured by a fiberoptic temperature sensor (Luxtron, Santa Clara, CA). Measurements were repeated on linear and circular lead configurations. The reproducibility of findings were evaluated by performing at least 3 different measurements per type and configuration. Further the dependence of the temperature rises on the position of the RF-coil relative to the lead configuration was examined. Results The temperature increases in the circular configuration (diameter 20cm, in the middle of the reservoir) exceeded 10°C in 2 leads and 15° in one lead (Figure 1). The rise time from room to maximal temperature was less than 10 seconds. 0 5 10 15 20 25 CapSure Fix 4068 CapSure Fix 4568 CapSure SP 4024 CapSure VDD 5032 CapSure Z 5034 Membrane E 1452T Tentril DX 1388T CapSure Z 4033 ThinLine Temperature increasing [°C] Circular Linear border Linear middle Figure 1: Temperature increase of different leads in circular configuration. In linear configuration the temperature increase depended strongly on whether the lead was placed in the middle of the reservoir or at the border. 5 leads touching the border were heated by more than 20°C, and the rest showed increases of more than 10°C. Under special configurations, linear at the border with the lead tip at the surface of the saline reservoir, a maximal temperature increase of as much as 69°C was observed. The bipolar ThinLine (Sulzer Intermedics Inc., Angleton, TX) lead with both conductors wound into a single coil showed repeatedly by far the least heating effects. The unipolar lead CapSure Z 4033 (Medtronic Inc., Minneapolis, MN) seemed to be better than the similarly designed bipolar CapSure Z 5034. By moving the lead and reservoir out of the isocenter of the RF coil the temperature changes could be reduced (Figure 2).
Contemporary cardiac pacemakers can fail from radiation damage at doses as low as 10 gray and can
exhibit functional changes at doses as low as 2 gray. A review and discussion of this potential
problem is presented and a protocol is offered that suggests that radiation therapy patients with
implanted pacemakers be planned so as to limit accumulated dose to the pacemaker to 2
gray. Although certain levels and types of electromagnetic interference can cause pacemaker
malfunction, there is evidence that this is not a serious problem around most contemporary
radiation therapy
equipment.
BACKGROUND. Electrosurgery is frequently employed in the treatment of skin cancer and other dermatologic conditions in the elderly. Implantable cardioverter-defibrillators (ICDs) and pacemakers are most commonly seen in this older population. Potentially hazardous electrosurgical interference exists with the function of ICDs and pacemakers in this setting. OBJECTIVE. Our goal is to review the potential hazards of electrosurgery in patients with ICDs and pacemakers and to suggest a perioperative management plan. METHODS. Review of the medical literature on electrosurgical interference with ICDs and pacemakers was accomplished in addition to a case report of ventricular tachycardia during Mohs surgery on a patient with an ICD. RESULTS. Multiple case reports and reviews from the nondermatologic literature demonstrate that a real hazard exists. CONCLUSION. Knowledge of the potential electrosurgical interference with ICDs and pacemakers is required to perform these procedures safely. A perioperative management plan is suggested. (C) 1998 by the American Society for Dermatologic Surgery, Inc.
Purpose:
The current clinical practice of shock wave lithotripsy is reviewed, specifically regarding patients in whom the presence of presumed absolute or relative contraindications may preclude treatment.
Materials and methods:
Peer reviewed basic scientific and clinical studies on shock wave lithotripsy in patients with urinary stones and concomitant conditions that might contraindicate treatment reported between 1982 and 1996 were critically reviewed.
Results:
The exclusion of patients with conditions previously believed to contraindicate shock wave lithotripsy has almost always been empiric rather than based on experimental or clinical studies showing adverse effects in those settings. The contemporary literature suggests that shock wave lithotripsy in patients with proximate calcified aneurysms, implanted cardiac pacemakers and defibrillators, and bleeding diatheses can be accomplished safely and effectively with careful treatment and monitoring before, during and after shock wave lithotripsy. Likewise, patients with morbid obesity, children, and those with mid and distal ureteral calculi can also be treated successfully, even with first generation lithotriptors, with minor modifications that allow for appropriate positioning of the patient and stone.
Conclusions:
The designation of most conditions as absolute or relative contraindications to shock wave lithotripsy has been empiric. A review of experimental and clinical studies pertinent to these issues clearly shows that most concomitant conditions previously precluding shock wave treatment can be circumvented to allow safe and effective use of this minimally invasive technology. Currently, pregnancy is the only condition that should remain an absolute contraindication to this treatment.
The most important application of electrical and computer engineering to medicine has been the artificial cardiac pacemaker. More than 500,000 implants at more than $2000 each has resulted in more than $1 billion in sales. This paper reviews how the heart works, its electric generators (natural pacemakers) and transmission (conduction system), how these fail, and how the artificial cardiac pacemaker can restore function. The ideal pacemaker measures the electrocardiogram in two chambers of the heart, supplies stimulation only when needed, stores information on irregular beats, transmits to a receiver when interrogated, and consumes 30 μW. The challenge now is to develop a rate-adaptive pacemaker that will deliver the increased heart rate required during exercise. Sensors measure body mechanical movement, increase in blood temperature, increase in breathing rate, or increase in electrical impedance, and use this information to control heart rate. Engineers are needed for work in sensors, circuits, computer technology, control systems, microelectronics, processing technology, and materials research.
Internal atrial defibrillation (IAD) has been extensively evaluated for clinical efficacy but the need for concomitant demand pacing and the effect of IAD shocks on pacemaker function is not well studied. We prospectively evaluated: (l) the incidence of bradycardia as a result of IAD shocks; and (2) effect of these shocks on functioning of implanted cardiac pacemakers. Consecutive consenting patients with atrial fibrillation (AF) requiring cardioversion or undergoing electrophysiologi-col study were selected for IAD. IAD shocks were delivered using the right ventricle to right atrium (RV-RA), right ventricle to superior vena cava (RV-SVC), right atrium to axillary patch (RA-AX), and right atrium to left pulmonary artery or coronary sinus (RA-LPA/CS) lead configurations. Mean RR interval before and after the shocks and the time interval from shock delivery to first QRS complex were analyzed for unsuccessful and successful shocks. Pacing and sensing function was analyzed in patients with previously implanted pacemakers. Twenty-five patients, 18 men, mean age 67.9 ± 10 years were included in the study. A total of 305 shocks (264 unsuccessful, 41 successful) were analyzed. For unsuccessful shocks the mean post-IAD shock RR interval (795 ± 205 ms) and the time to first post-IAD shock QRS complex (970 ± 438 ms) were both significantly greater than the pre-IAD shock RR interval (685 ±131 ms, P < 0.001). The increase in post-IAD shock RB interval and time to first post-IAD shock QRS complex was seen with all four lead configurations used. With successful shocks the mean post-IAD shock sinus cycle length (1.105 ± 450 ms) and time to first post-IAD shock QRS complex (1,126 ± 443 ms) were both also significantly greater than the pre-IAD shock RR interval (766 ±172 ms). Nine patients (36%) had episodes of significant bradycardia after shock delivery. Shocks of up to 20 J using the RA-LPA/CS lead configuration did not affect pacemaker function. IAD can result in transient bradycardia related to sinus and atrioventricular nodal effects requiring backup ventricular pacing. Shocks can be safely delivered using RA-LPA or RA-CS lead configurations in patients with implanted bipolar cardiac pacemakers.
Patients with permanent cardiac pacemakers occasionally require radiotherapy. Therapeutic irradiation may cause pacemakers to malfunction due to the effects of ionizing radiation or electromagnetic interference. Modern pacemakers, using complementary metal oxide semiconductor (CMOS) circuitry, differ from older bipolar semiconductor devices both in their sensitivity to damage and the types of malfunction observed. The mechanisms and types of radiotherapy-induced pacemaker malfunction are described and in vitro and in vivo studies of pacemaker irradiation are reviewed. Some simple precautions are recommended during the planning and administration of radiotherapy to minimize the risk of harm to patients with pacemakers.
Pacemaker malfunction occurred after a patient was given 3000–3600 rads to an area occupied by an A-V sequential pacemaker. Analysis of the removed generator showed that there was malfunction of the large scale integrated circuit and the type of damage was consistent with radiation-induced effects. The newer muJtiprogram-mable units may be more sensitive to ionizing radiation than those previously available. (PACE, Vol. 5, March-April, 1982)
A permanent demand pacing generator was implanted in the right deltopectoral fossa with unipolar transvenous lead advanced to the right ventricle. Implant and subsequent pacing parameters were normal. Five days later an emergency DC cardioversion was performed with one paddle 2 inches from the generator. Cardioversion was followed by failure of QRS-sensing and, at immediate explant, rise in stimulation threshold. The pulse generator showed end-of-life characteristics. The patient died 4 days following replacement of the generator and lead. At autopsy, right ventricular infarction was found, presumably relating to current discharge along the lead. Pacemaker analysis showed damage to the protection zener diode and oscillator integrated circuit of the generator during cardioversion.
Four demand-type pacemakers were exposed to therapeutic levels of â¶Â°Co radiation as well as to the electromagnetic fields associated with two betatrons and three linear accelerators. Results indicate that patients who have pacemakers implanted should not be treated with betatrons; linear accelerators should be used with extreme caution in treatment of these patients. Therapeutic levels of â¶Â°Co radiation (less than 7000 rad) produced no apparent malfunction on the units tested.
Electromagnetic interference from diathermy apparatus can be a real hazard in a patient with a demand pacemaker. A case is reported in which the cutting current of transurethral electrocautery deactivated an implanted pacemaker, while coagulating current did not alter pacemaker activity. Therefore frequent short bursts of cutting current were used for successful resection of the prostate. This case emphasizes the need for vigilant care of patients with demand pacemakers requiring transurethral resection.
Accidental production of arrhythmias and myocardial lesions, that have not been reported previously, are described after the use of electrocautery. These lesions develop in the presence of the catheter electrode in the right ventricle and ECG preamplifier input circuit. (Tosovsky - Prague)
Radiofrequency current catheter ablation was used successfully to create complete atrioventricular (AV) block in 60 of 61 patients (98%) with drug refractory supraventricular tachyarrhythmias. The remaining patient developed Mobitz I AV block and is clinically improved (clinical efficacy 100%). In 54 patients (89%), complete AV block was achieved using a right-sided approach. Patients aged > 60 years needed significantly fewer right-sided radiofrequency applications to produce complete AV block (5.3 +/- 5.3 vs 11.1 +/- 10.0; p = 0.009). In 6 of 7 patients with unsuccessful right-sided ablation, a left ventricular approach was used. In each case, 1 to 4 additional radiofrequency applications produced complete AV block. Patients with unsuccessful right-sided ablation were generally younger than those with successful ablation (50 +/- 16 vs 64 +/- 11; p = 0.007). It is concluded that catheter ablation using radiofrequency current is an extremely effective means of producing complete AV block. Older patients appear to be more susceptible to right-sided radiofrequency approaches. Left ventricular ablation easily produces complete AV block in patients refractory to right-sided attempts.
Radiofrequency current is being investigated as an alternative to direct current shock for transcatheter ablation of cardiac arrhythmias. Permanent pacemakers are known to be susceptible to high frequency electromagnetic interference. This study was performed to examine the effects of transcatheter radiofrequency ablation on permanent pacemakers in a worst-case scenario. Nineteen pulse generators representing 16 models from seven manufacturers were acutely implanted in 12 dogs to assess their function during and after ablation. Pulse generators were implanted subcutaneously in the neck and connected to a transvenous permanent pacing lead positioned in the right ventricular apex. A 6F quadripolar electrode catheter was positioned approximately 1 cm from the tip of the permanent pacing lead. Radiofrequency current from an electrosurgical unit was applied between the distal electrode of the catheter and a large diameter skin electrode placed below the left scapula. Three additional ablation sessions were performed with the catheter situated 4-5 cm from the permanent pacing lead. Each ablation consisted of 15 W of radiofrequency power, delivered for up to 30 seconds. Twelve pulse generators were falsely inhibited during radiofrequency ablation while programmed to the VVI or DDD mode, nine of which continued to be inhibited while programmed to the VOO or DOO mode. Five pulse generators paced at abnormal rates, including three examples of one pulse generator model that displayed pacemaker runaway. Runaway was observed during eight ablations, resulting in two episodes of ventricular fibrillation. Eleven pulse generators reverted to noise mode behavior during ablation. Only three pulse generators were unaffected during ablation. No reprogramming or pacing system malfunctions were observed after cessation of radiofrequency current application or during ablations greater than 4 cm from the permanent lead.(ABSTRACT TRUNCATED AT 250 WORDS)
We report a case of spinal cord stimulation (neurostimulation) as treatment for angina pectoris pain in a patient with a demand pacemaker. The precautions to avoid inhibition of the demand pacemaker by the neurostimulator are discussed.
A case of a unipolar surgical electrocautery-induced runaway pacemaker is described. The single chamber ventricular pacemaker began firing at 140 beats/min with intermittent capture and the abnormal rhythm persisted after cessation of the electrocautery. Emergent explanation of the pulse generator was required.
Determine the effect of percutaneous catheter ablation (CA) on permanent pacemakers.
Twenty-three patients who underwent CA at The Cleveland Clinic Foundation from September 1983 to January 1990, and had a previously implanted pacemaker were studied. Electrocardiographic data during the CA procedure and clinic data including pacemaker evaluations were analyzed. Fifty-two percent (12/23) of the pacemakers malfunctioned: five developed transient ventricular loss of capture; two undersensing; one oversensing; three could not be interrogated or programmed, and one did not respond to the magnet test. Four patients developed syncopal episodes and two severe dizziness after the procedure. All had their pacemakers replaced. In total, seven were explanted. Destructive analysis by the individual manufacturer identified pacemaker circuitry failure in five. Unipolar pacemakers and anodal ablation procedures had more frequent and severe malfunctions, but the difference was not statistically significant.
Pacemaker malfunction is frequent during CA. It may be prevented by programming the pacemaker, when possible, to the nonfunctioning mode (000 mode). Temporarily disconnecting the pacemaker during ablation requires further evaluation as an alternative approach. Close follow-up can detect pacemaker malfunction and prevent complications.
The effect of extracorporeal shock wave lithotripsy on the automatic implantable cardioverter defibrillator is unknown. To evaluate what effect might occur, a non-implanted automatic implantable cardioverter defibrillator was subjected to a full course of extracorporeal shock wave lithotripsy while inactive. Bench testing by the manufacturer after lithotripsy demonstrated normal function of the device. A patient with an automatic implanted cardioverter defibrillator who required contralateral extracorporeal shock wave lithotripsy then underwent this procedure. The right renal calculus was destroyed successfully with no apparent damage to the automatic implantable cardioverter defibrillator. A test of the automatic implantable cardioverter defibrillator after lithotripsy demonstrated normal sensing and conversion of induced ventricular tachycardia.
Twenty-three multiprogrammable pacemakers and four implantable cardioverter defibrillators (ICDs) containing either complementary metal-oxide semiconductor (CMOS) or CMOS/Bipolar integrated circuit (IC) technology were exposed to 6-MV photon and 18-MeV electron radiation at various dose levels. Of the 17 pacemakers exposed to photon radiation eight failed before 50 Gy, whereas four of the six pacemakers exposed to electron radiation failed before 70 Gy. Photon scatter doses were well tolerated. For the ICDs detection and charging time increased with accumulated radiation dose, the charging time increased catastrophically at less than 50 total pulses delivered when compared with the charging time of six implanted ICDs. Sensitivity and output energy delivered by the ICD pulse were constant during the test. It was found that devices using the shorter channel length IC technology (i.e., 3 microns CMOS) were per se harder to ionizing radiation than the devices using larger channel length IC technologies (i.e., either 8 microns CMOS or combined 5 microM CMOS/20 V Bipolar). In fact, none of the devices based on 3 microns CMOS IC technology failed before 76 Gy, which is above the highest dose level (70 Gy) normally used in radiation oncology treatments.
The use of transcutaneous electrical nerve stimulation (TENS) has increased in recent years for the management of chronic pain. One of its few contraindications is the presence of a cardiac pacemaker. Clinicians have recommended that cardiac monitoring be performed for a short interrupted period during the first application of TENS to ensure safety. We present two patients who were given trials of TENS for different chronic pain complaints. In both cases, electrocardiograms during the TENS trial did not reveal cardiac pacemaker dysfunction, but extended cardiac monitoring with the Holter monitor showed interference with pacemaker function. The abnormalities did not recur after reprogramming the sensitivity of the pacemakers. We suggest the use of extended cardiac monitoring for patients with cardiac pacemakers during the prolonged use of TENS to ensure safety and to determine any need for reprogramming of the pacemakers. Patients with cardiac pacemakers should not be excluded from the use of TENS, but careful evaluation and extended cardiac monitoring should be performed.
Patients with cardiac pacemakers currently are treated by extracorporeal shock wave lithotripsy only by agreement between individual physicians and patients. We present the results of a survey of patterns of extracorporeal shock wave lithotripsy treatment (or nontreatment) of patients with pacemakers in the United States and Europe. Letters of inquiry regarding treatment of pacemaker patients were sent to 141 United States extracorporeal shock wave lithotripsy sites and 55 sites in Europe. Responses were received from 81 (57%) and 17 (31%) sites, respectively. A total of 131 patients received 142 treatments and pacemaker-related complications occurred in 4 (none was lethal, 3 were minor and all were corrected immediately). No patient required replacement of the pacemaker. No correlation existed between complications and pacemaker type or manufacturer. Urologists who treat patients with a pacemaker required previous clearance of the patients by the cardiologist, a cardiologist in or near the extracorporeal shock wave lithotripsy suite and standby of corrective equipment or temporary pacemakers.
Twenty-two pacemaker pulse generators were exposed to shock waves of an extracorporeal shock wave lithotripter to assess the effects of the extremely high pressure transients on pacemaker function. The pulse generator and distal aspect of the lead were positioned 5 cm from the focal point of the lithotripter and 10 cm from each other. Pulse generator function was analyzed during shock wave delivery synchronized with pulse generator output, during shock waves at a rate faster than the escape rate, and after exposure to lithotripsy. During shock waves delivered synchronously with pulse generator output, only one of 22 pulse generators malfunctioned by intermittently reverting to the magnet rate. When subjected to shock waves at a rate greater than the escape rate, 50% of the pulse generators were inhibited by electromechanical interference from the lithotripter. Both bipolar and unipolar devices were affected. However, analysis after exposure to shock waves showed that none of the pacemakers was damaged or spuriously reprogrammed. In conclusion, cardiac pacemakers do not appear to be damaged or reprogrammed by exposure to extracorporeal shock wave lithotripsy. The likelihood of false inhibition appears to be very low if shock waves are delivered synchronously with the QRS.
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Effects of extracorporeal shock wave lithotripsy (ESWL) were studied on 15 pacemakers (standard single chamber n = 5, dual chamber n = 6, rate responsive single chamber [Activitrax] n = 4). In-vitro testing involved suspending the pacemakers in a bath of degassified, deionized water firmly taped to a platform at the point of maximal pressure, i.e., second focal point (F2), where they received pressure shocks (means = 1300) from the HM3 Dornier lithotriptor. The pacemakers, programmed to their most sensitive setting, were continuously pacing at nominal outputs (atrial and ventricular pacing in the DDD mode). All units were assessed by a pacing system analyzer before and after the study, then underwent destructive analysis. During standard single chamber pacing (VVI) the pacing stimulus triggered ESWL. For dual chamber devices, ESWL was triggered by the atrial paced event which induced inhibition of the ventricular output in two pacemaker. This was eliminated by reprogramming to a less sensitive setting. The pacemaker can, hermetic seal and internal circuitry were undamaged in all units. Two rate responsive single chamber pacemakers had their activity sensing piezoelectric elements shattered when placed at F2. Two other units placed 5 cm from F2 were stimulated to their maximum upper programmed pacing rate with ESWL therapy, but were otherwise unaffected. Subsequent to this study, six patients with pacemakers programmed to the VVI (five), DDD (one) modes implanted in the thorax underwent successful ESWL without pacemaker or arrhythmic event.
Conclusions:
(A) It is generally safe for patients implanted with standard single chamber devices in a ventricular application to undergo ESWL without modifying the pacing/sensing parameters. (B) Patients implanted with dual chamber devices who pace in the atrium should be reprogrammed to the VVI mode during ESWL. (C) Patients with piezoelectric activity sensing rate responsive single chamber pacemakers should have this feature programmed off during ESWL and, if implanted in the abdomen, probably should not undergo ESWL.
This study evaluated effects of extracorporeal shock wave lithotripsy on four models of Medtronic implantable cardiac pacemakers. In vitro testing consisted of: (1) unsynchronized pacemaker strapped on the patient with extracorporeal shock synchronized to the patient's native heart rate; and (2) pacemakers suspended alone in water 6 inches from the focal point, synchronizing the extracorporeal shock to pacemaker output. Unsynchronized shocks affected each model of pacemaker differently, i.e., single chamber constant rate pacemakers experienced extended periods of inhibition for more than three pacing cycles while activity-triggered rate response pacemakers exhibited rate increases to the upper rate setting. Dual chamber synchronous pacemakers exhibited intermittently a 59% decrease and a 20% increase in ventricular rate due to inhibition and triggering, respectively, from shock oversensing. Synchronized shocks did not alter the rate of single chamber constant rate pacemakers, but did cause the rate to increase to the upper rate setting for activity-triggered rate response pacemakers. The shock was synchronized to the initial atrial output from the dual chamber pacemaker and caused frequent inhibition of the ventricular stimulus when the ventricular-safety-pace (VSP) feature was programmed off. Programming VSP on reduced the incidence of ventricular inhibition resulting in near normal pacemaker operation. There was neither observable damage to pacemaker components nor spurious reprogramming of pacemaker parameters during the tests. Our studies with one manufacturer's pacemakers suggests that lithotripsy shock effects on implantable pacemakers can be tolerated provided: (1) the single chamber pacemaker is programmed to the demand constant rate modality; (2) the dual chamber pacemaker is programmed to VSP on or to the VVI mode; and (3) the pacemaker distance to the focal point is greater than 6 inches.(ABSTRACT TRUNCATED AT 250 WORDS)
Transient programmed upper limit stimulation (150 bpm) was observed during repetitively utilized electrocautery in the beginning of an open-heart surgical procedure in a patient with a minute ventilation rate responsive ventricular pacemaker. This tachycardia caused severe hemodynamic deterioration, and was also initiated by internal heart massage and manual ventilation. Considering the recommendations of the manufacturer, this series of serious events could have been prevented, when reprogramming to the inhibited mode had been executed in anticipation of the operation.
In 51 patients who had 20 different models of permanent cardiac pacemakers, we conducted transcutaneous electrical nerve stimulation studies at four anatomic sites--the lumbar area, cervical spine, left leg, and lower arm area ipsilateral to the pacemaker. With a mean stimulation of 24.7 Hz, no episodes of interference, inhibition, or reprogramming of the pacemakers occurred. The proximity of the stimulation site to the pulse generator had no effect. We did not study electrodes placed parallel to the pacemaker electrode vector, a position that has been of concern to others and that should probably be avoided until proved safe. On the basis of our findings, we believe that most patients with permanent cardiac pacemakers can safely undergo transcutaneous nerve stimulation.
External electromagnetic interference with cardiac pacemaker function is a recognized hazard of electronic instrumentation used for diagnosis or therapy. Although improved shielding and circuitry have made newer pacemakers less vulnerable to extraneous electronic artifact, their increasing use may expose more patients to the complications of electromagnetic interference. The effects of nerve conduction stimulation testing (NCST) on patients with cardiac pacemakers were evaluated both clinically and in the laboratory. Estimates of interference potentials likely to occur at a pacemaker input during NCST were made by making calculations from a theoretical model. For three different pacemakers, these estimates were compared to laboratory tests of sensitivity to interference. Some potential for pacemaker interference was shown to exist, although primarily with unipolar pacing leads. Twenty patients, five of whom were monitored electrocardiographically, underwent uneventful nerve conduction studies. Although pulse producing stimulators have the potential to affect demand type pacemakers, if current paths are confined within standard clinical parameters, untoward responses appear unlikely.
Patients with a permanent pacemaker are currently restricted from diagnostic nuclear magnetic resonance (NMR) imaging because of potential adverse effects on the pacemaker by the magnet. Previous work has shown that NMR imaging will result in asynchronous pacing of the pulse generator within a given distance of the magnet. The radiofrequency signal generated by the system may also result in rapid cardiac pacing, which may have deleterious effects. This study utilized a 1.5 tesla unit in an in vivo laboratory animal to evaluate the unit's effects on eight different pulse generators from two manufacturers. All pacemakers functioned in an asynchronous mode when placed within a certain distance of the magnet. In addition, transient reed switch inhibition was observed. Seven of the eight pulse generators paced rapidly when exposed to the radiofrequency signal and there was a dramatic decrease in arterial blood pressure. Whether effective rapid cardiac pacing would occur could not be predicted before exposure to the magnetic resonance unit. Nuclear magnetic resonance imaging with high magnetic fields in patients with a pacemaker should continue to be avoided until the mechanism of the rapid cardiac pacing can be further delineated and either predicted or prevented.
Both electrocautery and internal defibrillation are routinely used in cardiac operations. The cases of 5 patients are presented in whom backup-mode reversion or injury of permanently implanted pulse generators occurred during a cardiac procedure. The theoretical explanations for backup-mode reversion and generator or tissue injury are discussed, and recommendations are made for the management of patients with a pacemaker who are to undergo a cardiac operation.
Electrocautery, commonly used during surgery to maintain hemostasis, can have significant detrimental effects in the paced patient. Damage to the pulse generator, reprogramming of the pacemaker, changes in the capture threshold, and ventricular fibrillation can all be induced by electrocautery. Familiarity with the particular pacemaker in use is critical in minimizing these adverse effects. Preoperative evaluation of the patient's dependence on the pacemaker and evaluation of pacemaker function should be performed and documented. We recommend close intraoperative monitoring of heart rate and rhythm, and suggest that a pacemaker programmer be on hand in the surgical suite during the operation. A postoperative check of pacemaker function should be carried out so that electrocautery-induced pacemaker malfunction will not go unnoticed or uncorrected. Three cases are presented which clearly illustrate these points.
Pacemaker carriers are at risk when undergoing operations involving the use of diathermy. The Shaw Scalpel utilizes a method by which the cutting edge of the blade is heated to a selected temperature that seals blood vessels as they are cut. No electrical currents are passed to or through the patient and there is no sparking or electrical arcing to the tissue. This apparatus was used as the sole method of thermal coagulation in 20 patients undergoing replacement of pacemaker batteries.
Eight cardiac pacemakers were irradiated in a cobalt-60 beam. Two out of six demand-type pacemakers showed an alarming decrease in pulse repetition frequency when irradiated to dose levels that are used in radiotherapy (<100 Gy). Two modern programmable pacemakers showed a failure at a dose of 97 and 147 Gy, respectively. The dose levels at which these failures occurred were low enough to recommend that cardiac pacemakers should always be kept outside the radiation beam.
The signals induced by electromagnetic interference (EMI) from two linear accelerators were measured using a simulation model of a pacemaker. In the laboratory, 22 modern-type pacemakers were tested with these signals to determine the sensitivity for the electromagnetic fields in the treatment rooms. It was observed that an inhibition of one pacemaker pulse was to be expected on one of the two linear accelerators when switching the machine on and off. No permanent effects were found. These findings resulted in the recommendation in our department not to use this treatment machine for radiation therapy of pacemaker-bearing patients.
This case report presents an unusual complication involving the use of an electrocautery in a patient with a demand pacemaker. Placing a magnet over the pacemaker generator allowed electromagnetic waves from the electrocautery to randomly reprogram the pacemaker generator to different rates.
Six cases are presented in which a transient or chronic rise in the stimulation threshold of a permanently implanted unipolar pacemaker resulted in the loss of effective pacing after therapeutic defibrillation or cardioversion. Although damage to the pulse generator may still occur, leading to a loss of function as demonstrated in a seventh patient, improvements in the internal protection circuits of the present generation of pacemakers makes this less likely while possibly predisposing to endocardial burns and increased fibrosis at the electrode-endocardial interface. The theoretical explanations for this phenomenon are discussed, along with recommendations for the prospective and retrospective management of the pacemaker patient who requires defibrillation or cardioversion.
Patients with cardiac pacemakers are currently restricted from nuclear magnetic resonance imaging (MRI). The aim of the study was to analyze the influence of MRI on new generation pacemakers. Tests were performed using a phantom model with seven dual chamber and two single chamber systems in a 0.5 Tesla MRI scanner. Monitoring by telemetry and oscillography were used during the standard clinical scan sequences as well as a pacemaker inquiry after each sequence. Spin echo, gradient echo, and fast field echo sequences were performed with the following stimulation modes: VVI, VVIR, VOO, DDD, DDDR, and DOO. On entering the static magnetic field, the reed switch was activated followed by asynchronous stimulation. The subsequent scan showed no influence on the stimulation function nor on the pacemaker program. Event counter function remained intact. Pacemakers with automatic mode switching to demand pacing or programmed inactivation of the reed switch were triggered in the dual chamber mode and were inhibited in the one chamber mode during the scan. Alterations of pacemaker program or rapid pacing were not observed. MRI scan could induce voltage as high as intracardiac signals, but the stimulation threshold of the heart was not reached. Thus, pacemakers should be programmed in the asynchronous mode during scan to avoid inhibition and trigger mechanism.
Following successful RF ablation of the atrioventricular node (AVN), temporary pacing is necessary prior to insertion of a permanent pacemaker. The risks and inconvenience of temporary pacing could be avoided if a permanent pacemaker is already in place. This study reports the feasibility of RF ablation of the AVN in 27 patients (age 55 +/- 17 years, 15 males) with hypertrophic cardiomyopathy and pacemakers. Indications for AVN ablation were drug refractory atrial fibrillation in 24 patients, and rapid AVN conduction preventing septal pre-excitation by DDD pacemaker, inserted for relief of left ventricular outflow obstruction, in three cases. Sixteen patients had DDD devices and 11 patients had VVI devices. During RF ablation, each pacemaker was programmed to VVI at 50 beats/min. The ablation catheter was manipulated with fluoroscopic control to avoid close contact with or disturbance of the pacing leads. In 16 patients, RF ablation was performed immediately following pacemaker implantation but in the remaining patients, the AVN was ablated 6-32 months after pacemaker implantation. The power applied was 25-50 watts for a duration of 15-60 seconds. AV block was achieved in all cases but required 34 +/- 36 applications for 16.5 +/- 17.8 min/case. RF ablation consistently caused reversion to magnet rate in one patient and temporarily inhibited appropriate pacemaker discharge in another. However, no other pacemaker or lead malfunction was detected so that temporary pacing was not required in any case. At 6 +/- 3 months follow-up, all pacemakers were functioning normally without alteration in pacing parameters from baseline.(ABSTRACT TRUNCATED AT 250 WORDS)
It is well documented that radiation therapy can have significant transitory and permanent effects on the function of cardiac pacemakers. In this study 18 multiprogrammable pacemakers were tested to establish any pattern by which these pacemakers are affected. The results confirm previous predictions on how pacemakers are damaged. The damage could be divided essentially into three types: (1) temporary change to interference or safety mode pacing lasting for the duration of the irradiation only; (2) change to interference mode pacing--from which recovery may occur after reprogramming the pacemaker; and (3) severe damage; in this case the pacemaker stops generating pulses. Recovery from this may occur a long time after the end of the treatment, but this recovery is mostly incomplete and the pacemaker cannot be used reliably thereafter. Therefore it is essential that patients with implanted pacemakers undergoing radiation therapy, should be monitored closely during the course of the treatment and for a few weeks thereafter.
There are increasing numbers of radiofrequency current ablation procedures being reported. Selected patients have antitachycardia or antibradycardia pacemakers. The pacemaker behavior during and after ablation procedures differs widely. We report on the pacemaker reaction of 25 patients with 13 different devices, most with unipolar electrodes. Sensing failures were observed in 8 (32.0%) and pacing failures in 4 (16.0%) patients. Prolonged pauses and induction of tachyarrhythmias were observed. No pacemaker damage was seen although it is reported by other investigators. We recommend deactivation of implanted generators and an external bipolar pacing electrode. Manufacturers should focus their attention on this problem and protect the generators and their functions for 500 kHz radiofrequency current.
Extracorporeal shock wave lithotripsy (ESWL) is frequently used for nephrolithiasis of the upper urinary tract. Because of the powerful shock wave and electromechanical forces created, this therapy has been contraindicated in the patient with an implantable cardioverter defibrillator (ICD). To determine whether or not ESWL affects ICD devices, we subjected ten devices to a full course of ESWL. The devices were then returned to the manufacturer to undergo bench analysis, which revealed no abnormalities in function. Additionally, one device was placed in the pathway of the shock wave, resulting in a discharge of the device despite a frequency of ESWL of 100 shocks/min (well below the rate cutoff of that device). Manufacturer analysis of this device, likewise, revealed no abnormalities even though the device had been exposed to the focal point of the shock wave. We conclude that contralateral ESWL is not contraindicated for the patient with an ICD. We do, however, recommend a post-procedure evaluation to ensure appropriate function of the ICD.
Spinal cord stimulators are used to relieve pain associated with peripheral ischemia and angina pectoris. In patients with both permanent pacemaker (PPM) and a spinal cord stimulator (SCS), electromagnetic signals from the SCS may inhibit the PPM. A bipolar PPM configuration is preferred to minimize myopotential or electromagnetic interference but patients have safely had unipolar devices implanted. We report ten patients (six males and four females; median age 73.3 years) with both a SCS and a PPM implanted between 1987-1991. Intermittent interference with one PPM (Ela Medical Model Opus 3001) was noted after an increase in the output voltage of the SCS for continued clinical efficacy. Inhibition was output voltage dependent, and reversion to the noise mode was frequency dependent. Sensitivity to both could be managed by changing the pacemaker sensitivity. Interference with pacemaker function occurred if the SCS output was set above a voltage and pulse duration which resulted in a product of these values above 1.9-2 mVs. Seven VVI, one VDD, and two DDD PPM had been implanted. In five patients both PPM and SCS were unipolar. In two patients the SCS was bipolar and the PPM unipolar, in two patients a bipolar PPM was associated with a bipolar SCS and with one patient, a unipolar SCS. Multiprogrammable and/or bipolar PPMs should be implanted in a patient with a SCS to allow reprogramming of the PPM and to minimize the risk of inter-device interference. Inhibition of the PPM may occur at different SCS stimulation frequencies. The frequency at which inhibition occurs varies with different models of implanted pacemaker.
Implanted cardiac devices, pacemakers, and automatic cardioverter/defibrillators are becoming more common in the general population. There are more than one-half million persons with pacemakers living in North America, and approximately 20,000 patients have received automatic implantable cardioverter/defibrillators. As pacemaker and defibrillator patients experience common gastrointestinal afflictions, it is likely that more will require endoscopic procedures. Appropriate precautions must be undertaken during electrosurgical procedures in order to avoid damage and interruption of pacemaker/defibrillator devices. Through careful assessment, intervention, and discharge planning, the GI nurse and associate can reduce electrosurgical risks to the gastrointestinal patient with an implanted cardiac device. Specific recommendations for preprocedure patient assessment and intraprocedure interventions are discussed, and an actual case is presented to illustrate a successful plan of care.
A 58-year-old man with an implanted minute ventilation rate adaptive DDD pacemaker underwent RF ablation of the AV junction because of symptomatic supraventricular tachyarrhythmias. Immediately after ablation, while the pacemaker was programmed in the DDDR mode, AV sequential pacing at upper rate was observed. After programming the pacing system to the DDD mode and repeated ablation, no abnormalities were observed. It was concluded that AV sequential upper rate pacing was caused by false interpretation of the RF current by the sensor measuring transthoracic impedance as an indicator for minute ventilation.
Magnetic resonance (MR) procedures are contraindicated for patients with certain ferromagnetic biomedical implants, primarily owing to the risk of movement or dislodgment of the implants by the static magnetic field. An additional concern is the amount of artifact that the implant produces, which can affect image quality and interpretation of the examination. Therefore, an ex vivo assessment of ferromagnetism and artifact was conducted for 12 different occluders used to treat patients with patent ductus arteriosus, atrial septal defects, and ventricular septal defects, in a 1.5-T MR system. Seven of the occluders, made of 304 stainless steel, were ferromagnetic and displayed deflection forces of 248-299 dynes. Five of the implants, made of MP35n, were nonferromagnetic. Artifacts were variable and depended primarily on the type and amount of metal used to construct the implant. The authors conclude that patients with ferromagnetic cardiac occluders may undergo MR procedures approximately 6 weeks after placement of these devices, to allow tissue growth to provide additional retentive force. After this time, it is highly unlikely that the magnetic fields associated with a 1.5-T MR system are capable of moving or dislodging any of these cardiac occluders.
Electromagnetic interference usually produces only minor effects in patients with pacemakers. Nevertheless, the possibilities of serious and even fatal consequences of this complication must be recognised. This case reports an unusual anaesthetic source of interference, caused by activation of a popular nerve stimulator, resulting in cardiac arrest in a patient with a fixed-rate ventricular pacemaker.
Lithotripsy treatment of urinary tract calculi initially excluded patients with cardiac pacemakers. Continued research and clinical study of patient outcomes has promoted a change in that initial concept. The Oklahoma Lithotripsy Center has successfully treated 20 patients with various types of pacemakers. No significant cardiovascular events occurred during treatment. Patients should be evaluated before the procedure by a cardiologist, and dual-chamber pacemakers should be reprogrammed to the single-chamber mode. Patients who cannot tolerate this should not undergo SWL. Rate-responsive pacemakers should be programmed to the non-rate-responsive (VVI) mode. The pacemaker should be at least 5 cm from the blast path. With these precautions and careful monitoring, SWL can be performed safely in most patients with pacemakers.