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ABSTRACT: Muscle function assessment is important for diagnosing muscular disorders, developing treatment plans, and tracking patient progress over time. The muscle force assessment system (MFAS) can provide quantitative results versus the traditional qualitative results that are obtained from manual tests. A new MFAS was developed for measuring force in the tibialis anterior muscle in response to electrical stimulation. The system is small, portable, and can be used in an ICU setting. Preliminary experiments were conducted to compare the new system to an existing force assessment system. The results demonstrated that the new system is repeatable and reliable.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 01/2010; 2010:5835-8.
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ABSTRACT: Anesthetic choice for patients with chloride channel myotonia remains under debate. The authors have, therefore, investigated the in vitro effects of various anesthetic agents on pharmacologically induced chloride channel myotonia.
Functionally viable (> 10 mN force generation) rectus abdominis muscle preparations obtained from normal swine were investigated using in vitro muscle contracture test baths. During continuous 0.1-Hz supramaximal electrical stimulation, the chloride channel blocker 9-anthracenecarboxylic acid (64 microM) was added before the addition of propofol or one of three volatile anesthetics. The concentration of propofol in either Intralipid (n = 11) or dimethyl sulfoxide (n = 10) was doubled every 10 min (from 4-512 microM). The concentration of halothane (n = 8), isoflurane (n = 8), and sevoflurane (n = 8) was doubled from 0.25 vol% up to the maximum dose according to calibrated vaporizers. Control muscle bundles were either untreated (n = 30) or exposed to 9-anthracenecarboxylic acid (n = 19).
The myotonic reactions induced by 9-anthracenecarboxylic acid were reversed by high-dose (> 64 microM) propofol (P < 0.01). Halothane, isoflurane, or sevoflurane each enhanced the myotonic reactions at 5.4 (P < 0.001), 0.21 (P < 0.01), and 0.5 minimum alveolar concentrations (P < 0.05), respectively.
The authors' in vitro data imply that propofol administration for general anesthesia may be better suited for patients with chloride channel myotonia versus volatile anesthetics. In isolated swine skeletal muscle bundles, propofol elicited a reversal of 9-anthracenecarboxylic acid-induced chloride channel myotonia, whereas volatile anesthetics further increased the associated myotonic reactions.
Anesthesiology 09/2009; 111(3):584-90. · 5.36 Impact Factor
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ABSTRACT: Right ventricular (RV) pacing has been associated with abnormal cardiac electrical and mechanical dyssynchrony, resulting in impaired global and regional ventricular pump function. This study aimed to characterize the relative effects of pacing site on left ventricular (LV) activation patterns and associated hemodynamic performances.
Acute pacing was performed in anesthetized swine (n=10) instrumented for RV and LV pressure, noncontact mapping (NCM) of endocardial unipolar electrograms, surface ECG, aortic flow, and sonomicrometry. Bipolar endocardial pacing leads were positioned in the right atrial appendage (RAA), RV apex (RVA), and RV outflow tract (RVOT), while bipolar epicardial leads were positioned on the LV-free wall (LVFW) and LV apex (LVA).
LVFW and RVA pacing induced the largest increase in intraventricular electrical dyssynchrony (IVED; 32.2+/-10 ms, 21.7+/-4.1 ms, respectively; both p<0.01), whereas pacing from all sites increased QRS and total endocardial LV activation durations (p<0.01). The largest impairment of LV and RV contractility (dP/dtmax) and relaxation (dP/dtmin) was observed during RVA pacing (p= ns). Synchronous electrical activation patterns were observed on NCM during RVOT and LVA pacing. LVFW pacing was the only site that significantly increased tau values as compared to RAA pacing (approximately 25%), whereas LVA pacing elicited only slight increases (approximately 1%).
In swine with preserved ventricular conduction, in vivo pacing of the RVOT and LVA was associated with preserved, physiologically similar electrical activation sequences and LV function relative to RAA pacing. In contrast, RVA pacing caused widespread electrical dyssynchrony of the LV and prolonged activation durations, thereby impairing associated cardiac performance. Such insights into alternate site cardiac pacing, which employed the combination of high-resolution electrical mapping with real-time hemodynamic assessments, may further increase acute and long-term benefits in patients requiring permanent pacemaker support.
Journal of Interventional Cardiac Electrophysiology 09/2009; 26(3):185-94. · 1.17 Impact Factor
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ABSTRACT: In vivo thermoregulatory temperature response to radio frequency (RF) heating at 9.4T was studied by measuring temperatures in nine anesthetized swine. Temperatures were measured in the scalp, brain, and rectum. The RF energy was deposited using a four-loop head coil tuned to 400.2 MHz. Sham RF was delivered to three swine to understand the thermal effects of anesthesia (animal weight = 54.16 kg, SD = 3.08 kg). Continuous wave (CW) RF energy was delivered to the other six animals for 2.5-3.4 h (animal weight = 74.01 +/- 26.0 kg, heating duration = 3.05 +/- 0.29 h). The whole-head specific absorption rate (SAR) varied between 2.71 W/kg and 3.20 W/kg (SAR = 2.93 +/- 0.18 W/kg). Anesthesia caused the brain and rectal temperatures to drop linearly. Altered thermoregulatory response was detected by comparing the difference in the temperature slopes before and after the RF delivery from zero. RF heating statistically significantly altered the rate of cooling down of the animal. The temperature slope changes correlated well with the RF energy per unit head weight and heating duration, and the maximum rectal temperature change during heating in heated animals. The temperature slope changes did not correlate well to the whole-head average SARs.
Magnetic Resonance in Medicine 08/2009; 62(4):888-95. · 2.96 Impact Factor
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ABSTRACT: Several methodologies are typically employed to extract chronically-implanted pacing leads including: laser catheter systems, radio frequency catheters, mechanical cutting catheters, and/or direct traction. In the present study, Visible Heart(R) methodologies were employed to obtain novel internal and external views of such extractions. Utilizing standard cardioplegia procedures, canine hearts (n = 3) with chronically-implanted endocardial pacing leads were explanted to a unique isolated heart apparatus. Modified Krebs-Henseleit buffer allowed for clear endocardial imaging with endoscopic video cameras inserted into the cardiac chambers. Leads were extracted using: (1) laser system with sheath; (2) dissection sheath with incorporated bipolar tungsten electrode; (3) non-powered mechanical sheath; or (4) direct traction. Resultant images provide a novel perspective regarding lead extraction methodologies and the imposed force on an encapsulated lead and on the great vessels and/or heart itself; this understanding may improve the outcome and safety of future lead extractions.
Journal of Interventional Cardiac Electrophysiology 11/2008; 24(1):27-31. · 1.17 Impact Factor
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ABSTRACT: The purpose of this study was to quantify and characterize venous valves within the major left ventricular (LV) veins of human hearts.
Fiberscope cameras were inserted into the coronary sinus and were manipulated to major LV coronary veins of perfusion fixed human hearts (n = 26). Observed venous valves were categorized by type and location and compared among the major LV veins.
Discernible venous valves were present in 23 of 26 examined hearts (89%); altogether, 105 valves were identified. Sixty-one of the valves were observed at the ostia to smaller branch veins (58% of all valves observed).
Coronary venous valves could hinder or aid in the advancement of guide wires, catheters, and/or the placement of leads for a variety of cardiac interventional procedures. The characterization and quantification of venous valves could explain the difficulty or success in accessing targeted coronary venous locations.
Journal of Interventional Cardiac Electrophysiology 09/2008; 23(2):95-9. · 1.17 Impact Factor
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ABSTRACT: A noninvasive three-dimensional (3D) cardiac electrical imaging (3DCEI) approach, which can estimate the location of the initiation site (IS) of activation and the resultant 3D activation sequence (AS) from body surface potential maps (BSPMs), was validated in an intact large mammalian model (swine) during acute ventricular pacing. Body surface potential mapping and intracavitary noncontact mapping (NCM) were performed simultaneously during pacing from both right ventricular (RV) sites (intramural) and left ventricular (LV) sites (endocardial). Subsequent 3DCEI analyses were performed on the measured BSPMs. In total, 5 RV and 5 LV sites from control and heart failure animals were paced. The averaged localization error of the RV and LV sites were 7.0+/-1.1 mm and 6.6+/-1.9 mm, respectively. The endocardial ASs as a subset of the estimated 3D ASs by 3DCEI were consistent with those reconstructed from the NCM system. The present experimental results demonstrate that the noninvasive 3DCEI approach can localize the initiation site and estimate cardiac activation sequence with good accuracy in an in vivo setting, under control, paced and/or diseased conditions.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2008; 2008:4544-7.
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ABSTRACT: In vivo temperatures were correlated to the whole head average specific absorption rate (SAR(avg)) at 9.4T using 12 anesthetized swine (mean animal weight = 52 kg, standard deviation = 6.7 kg). Correlating the temperatures and SAR(avg) is necessary to ensure safe levels of human heating during ultra-high field MR exams. The temperatures were measured at three depths inside the brain, in the rectum, and at the head-skin of swine. A 400 MHz, continuous wave RF power was deposited to the head using a volume coil. The SAR(avg) values were varied between 2.7-5.8 W/kg. The RF power exposure durations were varied between 1.4-3.7 hr. To differentiate the temperature response caused by the RF from that of the anesthesia, the temperatures were recorded in four unheated swine. To study the effect of the spatial distribution of the RF and tissue properties, the temperature probes were placed at two brain locations (n = 4 swine for each location). Results showed that the in vivo brain temperatures correlated to the SAR(avg) in a geometry-dependent manner. Additionally, 1) the skin temperature change was not the maximum temperature change; 2) the RF heating caused an inhomogeneous brain temperature distribution; and 3) the maximum temperature occurred inside the brain.
Magnetic Resonance in Medicine 02/2008; 59(1):73-8. · 2.96 Impact Factor
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ABSTRACT: Over 15 million Americans are affected by coronary heart disease, according to the American Heart Association. Approximately 8 million have suffered a myocardial infarction. The economic and social consequences of this disease are staggering. A plethora of experimental and established therapies exist for this disease, such as stem cell therapy, growth factor injection, engineered cell transfection, etc. The use of these techniques relies on targeted therapeutic delivery. This paper describes mathematical techniques to extract key features from acquired action potential signals from ischemic and normal regions of the same heart. Using a modified means clustering technique on paired data, the best features are evaluated in multidimensional space. The results indicate promising clustering and separation of ischemic and normal beats using frequency domain computations, morphology analyses, and isoelectric point evaluations. Features were tested with data collected from a swine model of localized ischemia implanted with transmural electrodes and evaluated with a cross-validation approach. This research may have clinical significance to aid in the efficacious diagnosis or treatment of myocardial ischemia.
Conference proceedings: ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Conference 02/2007; 2007:3856-9.
