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ABSTRACT: While right ventricular (RV) dysfunction has long been known to affect the performance of left ventricle (LV), the mechanisms remain poorly defined. Recently, speckle-tracking echocardiography (STE) has demonstrated that preservation of strain and rotational dynamics is crucial to both LV systolic and diastolic function. We hypothesized that alteration in septal strain and rotational dynamics of the LV occurs during acute RV pressure overload (RVPO), and leads to decreased cardiac performance. Seven anesthetized pigs underwent median sternotomy and placement of intraventricular pressure-volume (PV) conductance catheters. 2D-echocardiographic images and LV PV loops were acquired for offline analysis at baseline and after banding of the pulmonary artery to achieve RVPO (>50 mmHg) induced RV dysfunction. RVPO resulted in a significant decrease (p<0.05) in LV end systolic elastance (50%), +dP/dtmax (19%), EDV (22%), and cardiac output (37%) that correlated with decrease in LV global circumferential strain (58%), LV apical rotation (28%), peak untwisting (reverse rotation) rate (27%) and prolonged time to peak rotation (17%), while basal rotation was not significantly altered. RVPO reduced septal radial and circumferential strain, while no other segment of the LV midpapillary wall was affected. RVPO decreased septal radial strain on LV side by 27% and induced a negative radial strain from 28±5% to -16±2% on the RV-side of the septum. The septal circumferential strain on both LV and RV-side decreased by 46% and 50%, respectively following RVPO (p<0.05). Our results suggest that acute RVPO impairs LV performance by primarily altering septal strain and apical rotation.
Journal of Applied Physiology 05/2013; · 3.75 Impact Factor
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ABSTRACT: BACKGROUND: Assessment of left ventricular rotational mechanics and myocardial deformation may provide new insight into both systolic and diastolic function. However, the effects of increasing afterload on these measures of cardiac function are poorly understood. The aim of this study was to identify the changes in left ventricular function and rotational mechanics during increasing pharmacologic afterload. METHODS: In 14 anesthetized rabbits, two-dimensional speckle-tracking echocardiographic images and left ventricular pressure-volume loops were acquired at baseline and during norepinephrine, phenylephrine, and vasopressin infusion at increasing doses. Maximal ventricular elastance, arterial elastance, ventricular-arterial coupling, dP/dt, the time constant of relaxation, and other hemodynamic parameters were determined. RESULTS: An increase in dP/dtmax with norepinephrine and phenylephrine and a decrease with vasopressin at escalating doses were detected. Ventricular-arterial coupling was preserved with norepinephrine and phenylephrine but decreased with vasopressin (P < .05). Apical rotation, rotational rate, and strain were preserved during the norepinephrine and phenylephrine infusions but were reduced with vasopressin (P < .05). Apical rotation and circumferential strain were significantly correlated with both ventricular-arterial coupling (r = 0.84 and r = 0.81) and dP/dtmax (r = -0.81 and r = -0.77). High-dose vasopressin decreased the diastolic time constant of relaxation and dP/dtmin while reducing apical untwisting rate. CONCLUSIONS: Pharmacologic increases in afterload with vasopressin resulted in greater derangements in ventricular-arterial coupling and cardiac performance compared with norepinephrine and phenylephrine. Rotation and strain correlated well with invasively determined measures and can be used to assess afterload-induced alteration in cardiac function.
Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography 04/2013; · 2.98 Impact Factor
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ABSTRACT: BACKGROUND:Red blood cell (RBC) transfusions are associated with increased morbidity. Children receiving heart transplants constitute a unique group of patients due to their risk factors. Although previous studies in nontransplant patients have focused primarily on the effects of postoperative blood transfusions, a significant exposure to blood occurs during the intraoperative period, and a larger percentage of heart transplant patients require intraoperative blood transfusions when compared with general cardiac surgery patients. We investigated the relationship between clinical outcomes and the amount of blood transfused both during and after heart transplantation. We hypothesized that larger amounts of RBC transfusions are associated with worsening clinical outcomes in pediatric heart transplant patients.METHODS:A database comprising 108 pediatric patients undergoing heart transplantation from 2004 to 2010 was queried. Preoperative and postoperative clinical risk factors, including the amount of blood transfused intraoperatively and 48 hours postoperatively, were analyzed. The outcome measures were length of hospital stay, duration of tracheal intubation, inotrope score, and major adverse events. Bivariate and multivariate analyses were performed to control for simultaneous risk factors and determine outcomes in which the amount of blood transfused was an independent risk factor.RESULTS:Ninety-four patients with complete datasets were included in the final analysis. Eighty-eight percent received RBC transfusions, with a median transfusion amount of 38.7 mL/kg. A multivariate analysis correcting for 8 covariate risk factors, including the Index for Mortality Prediction After Cardiac Transplantation, age, weight, United Network for Organ Sharing status, warm and cold ischemia time, repeat sternotomy, and pretransplant hematocrit, showed RBC transfusions were independently associated with increased length of intensive care unit stay (means ratio = 1.34; 95% confidence interval, 1.03-1.76; P = 0.03), and increased inotrope score in the first postoperative 24 hour (mean ratio = 1.26; 95% confidence interval, 1.04-1.52; P = 0.04). Patients suffering major adverse events received significantly larger median amounts of blood RBC transfusions (P = 0.002). Transfusions >60 mL/kg were also associated with increased risk of major adverse events (accuracy 76%) including postoperative sepsis, extracorporeal membrane oxygenation, open chest, dialysis, and graft failure.CONCLUSION:The majority of pediatric patients undergoing orthotropic heart transplantation receive RBC transfusions, with the largest amount transfused in the operating room. Escalating amounts of RBC transfusions are independently associated with increased length of intensive care unit stay, inotrope scores, and major adverse events. Since heart allografts are a limited resource, improvement in the blood transfusion and conservation practices can enhance clinical outcomes in pediatric heart transplant patients.
Anesthesia and analgesia 04/2013; · 3.08 Impact Factor
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The Journal of thoracic and cardiovascular surgery 10/2012; · 3.41 Impact Factor
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ABSTRACT: Background- Intramyocardial nerve sprouting after myocardial infarction is associated with ventricular arrhythmias. Whether human stellate ganglia remodel in association with cardiac pathology is unknown. The purpose of this study was to determine whether cardiac pathology is associated with remodeling of the stellate ganglia in humans. Methods and Results- Left stellate ganglia were collected from patients undergoing sympathetic denervation for intractable ventricular arrhythmias and from cadavers, along with intact hearts. Clinical data on patients and cadaveric subjects were reviewed. We classified ganglia from normal, scarred, and nonischemic cardiomyopathic hearts without scar as NL (n=3), SCAR (n=24), and NICM (n=7), respectively. Within left stellate ganglia, neuronal size, density, fibrosis, synaptic density, and nerve sprouting were determined. Nerve density and sprouting were also quantified in cadaveric hearts. Mean neuronal size in normal, scarred, and nonischemic cardiomyopathic hearts without scar groups were 320±4 μm(2), 372±10 μm(2), and 435±10 μm(2) (P=0.002), respectively. No significant differences in neuronal density and fibrosis were present between the groups. Synaptic density in ganglia from SCAR and NICM groups were 57.8±11.2 μm(2)/mm(2) (P=0.084) and 44.5±7.9 μm(2)/mm(2) (P=0.039), respectively, compared with the normal group, 17.8±7 μm(2)/mm(2) (overall P=0.162). There were no significant differences in left stellate ganglia nerve sprouting or myocardial nerve density between the groups. Conclusions- Neuronal hypertrophy within left stellate ganglia is associated with chronic cardiomyopathy in humans. Ganglionic and myocardial nerve sprouting and nerve density were not significantly different. These changes may be related to increased cardiac sympathetic signaling and ventricular arrhythmias. Further studies are needed to determine the electrophysiological consequences of extracardiac neuronal remodeling in humans.
Circulation Arrhythmia and Electrophysiology 08/2012; 5(5):1010-116. · 6.46 Impact Factor
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Expert Review of Cardiovascular Therapy 08/2012; 10(8):947-9.
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ABSTRACT: The clinical utility of focused transthoracic echocardiography (TTE) is increasingly recognized in perioperative medicine. However its use is limited among anesthesiologists because of a lack of training. The most efficient training methods have not been determined. We hypothesized that simulation-based TTE training would be more effective than traditional lecture-based methods for teaching basic TTE skills to the anesthesiology residents.
In this prospective randomized study, 61 anesthesiology residents (in anesthesia clinical training years 1 to 3) were randomized to either control (n = 30) or simulation groups (n = 31) for TTE training. A standardized pretest was administered before TTE training sessions of 45 minutes each. The first training session used a lecture-based video didactic in the control group or a TTE simulator in the simulation group. Comprehension in both groups was then assessed using a written posttest and by performing a TTE examination on a volunteer subject. TTE examinations were graded on the ability to acquire the correct image, image quality, anatomy identification, and time required to attain proper imaging by 2 blinded experts. A second training session incorporating "hands-on" training with a volunteer subject was conducted in a subset of 21 residents (n = 11 control, n = 10 simulation). The simulation group included additional simulator training. After the second session, another posttest on a volunteer subject was administered.
Pretest scores revealed similar preintervention knowledge among residents (56.0% ± 11.9% vs 59.3% ± 11.0%, P = 0.25; control versus simulator group, respectively). The simulation group scored higher on all criteria after the first training session: written posttest (57.9% ± 8.8% vs 68.2% ± 10.1%; P < 0.001), volunteer subject posttest image quality scores (0 to 25 scale) (6.4 ± 3.5 vs 12.4 ± 4.2; P = 0.003), anatomy identification scores (0 to 25 scale) (8.3 ± 6.6 vs 17.8 ± 6.6; P = 0.003), and percentage correct views (50 ± 19 vs 78 ± 21; P < 0.001). After the second session, all scores were again improved in the simulation group: volunteer subject posttest image quality scores (9.6 ± 3.3 vs 15.6 ± 2.8; P = 0.002), anatomy identification scores: (17.6 ± 3.8 vs 22.8 2.4; P = 0.003), and percentage correct views (80 ± 16 vs 96 ± 8; P = 0.007).
This prospective randomized study demonstrated that anesthesiology residents trained with simulation acquired better skills in TTE image acquisition and anatomy identification on volunteer subjects. The educational benefit of simulation persisted even with introduction of hands-on instruction with volunteer subjects in both groups. The impact of these short-term educational approaches on longer-term retention and actual clinical application warrants further investigation.
Anesthesia and analgesia 07/2012; 115(5):1042-51. · 3.08 Impact Factor
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ABSTRACT: Cardiac arrhythmias are a major source of morbidity and mortality. Many of these patients require diagnostic or therapeutic intervention in an electrophysiology laboratory with involvement of an anesthesiologist. The goal of this review is to provide the anesthesiologist with a comprehensive understanding of the mechanisms underlying various arrhythmias; specific procedures performed for diagnosis and treatment, and associated risks.
With the introduction of new interventional electrophysiology techniques, anesthesiologists are facing new challenges during perioperative management of these complex procedures and patients.
By reviewing the current literature regarding electrophysiology procedures, this review will provide information essential to the anesthesiologist to safely care for this unique patient population.
Current opinion in anaesthesiology 06/2012; 25(4):470-81.
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Journal of the American College of Cardiology 01/2012; 59(1):91-2. · 14.16 Impact Factor
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International anesthesiology clinics 01/2012; 50(2):90-110.
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ABSTRACT: The role of continuous central venous oxygen saturation (ScvO₂) oximetry during pediatric cardiac surgery for predicting adverse outcomes is not known. Using a recently available continuous ScvO₂ oximetry catheter, we examined the association between venous oxygen desaturations and patient outcomes. We hypothesized that central venous oxygen desaturations are associated with adverse clinical outcomes.
Fifty-four pediatric patients undergoing cardiac surgery were prospectively enrolled in an unblinded observational study. ScvO₂ was measured continuously in the operating room and for up to 24 h post-Intensive Care Unit admission. The relationships between ScvO₂ desaturations, clinical outcomes, and major adverse events were determined.
More than 18 min of venous saturations less than 40% were associated with major adverse events with 100% sensitivity and 97.6% specificity. Significant correlations resulted between the ScvO₂ area under the curve less than 40% and creatinine clearance at 12 h in the Intensive Care Unit (r = -0.58), Intensive Care Unit length of stay (r = 0.56), max inotrope use (r = 0.52), inotrope use at 24 h (r = 0.40), inotrope index score (r = 0.39), hospital length of stay (r = 0.36), and length of intubation (r = 0.32).
We demonstrate that ScvO₂ desaturations by continuous oximetry are associated with major adverse events in pediatric patients undergoing cardiac surgery. The most significant associations with major adverse events are seen in patients with greater than 18 min of central venous saturations less than 40%. Our results support the further investigation of ScvO₂ as a potential target parameter in high-risk pediatric patients to minimize the risk of major adverse events.
Anesthesiology 09/2011; 115(5):1033-43. · 5.36 Impact Factor
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Journal of cardiothoracic and vascular anesthesia 09/2011; 26(2):291-301. · 1.06 Impact Factor
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ABSTRACT: Activation of cardiac sympathetic nerves alters ventricular repolarization; however, these changes remain poorly characterized. The goal of this study was to examine effects of sympathetic stimulation on repolarization to identify electrocardiographic markers of sympathetic activation. Pigs underwent median sternotomy and bilateral thoracotomy to expose the stellate ganglia. Changes in T-wave duration, amplitude, repolarization vector, and time from peak to end (Tp-Te) were continuously monitored. Within 15 seconds of unilateral left or right stellate ganglion (LSG/RSG) stimulation, T-wave amplitude increased 6- and 4.5-fold, respectively, in lead aVF. T-wave duration and Tp-Te both increased 200% during LSG stimulation but only 50% and 30%, respectively, with RSG stimulation. During LSG stimulation, frontal and horizontal T-wave vectors, respectively, changed from 1.9° ± 22.8° and 333.8° ± 9.7° at baseline to 83.4° ± 3.9° (inferiorly) and 306.7° ± 1.8° (posteriorly). During RSG stimulation, frontal and horizontal T-wave vectors changed from 348.2° ± 21.6° and 333.8° ± 10.3° before stimulation to 280.7° ± 4.6° (superiorly) and 118.1° ± 5.6° (anteriorly). During stellate stimulation, T-wave vectors are displaced to angles specific for LSG activation (posteroinferiorly) or RSG activation (anterosuperiorly); T-wave amplitude, duration, and Tp-Te increase; and ST-duration decreases. Displaced repolarization vector and changes in T-wave morphometrics provide a novel marker of unilateral sympathetic nerve stimulation.
Journal of electrocardiology 09/2011; 44(6):694-9. · 1.08 Impact Factor
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Chi Hyung Seo,
Douglas N Stephens,
Jonathan Cannata,
Aaron Dentinger,
Feng Lin,
Suhyun Park,
Douglas Wildes,
Kai E Thomenius,
Peter Chen,
Tho Nguyen,
Alan de La Rama,
Jong Seob Jeong, Aman Mahajan,
Kalyanam Shivkumar,
Amin Nikoozadeh,
Omer Oralkan,
Uyen Truong,
David J Sahn,
Pierre T Khuri-Yakub,
Matthew O'Donnell
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ABSTRACT: A method is introduced to monitor cardiac ablative therapy by examining slope changes in the thermal strain curve caused by speed of sound variations with temperature. The sound speed of water-bearing tissue such as cardiac muscle increases with temperature. However, at temperatures above about 50°C, there is no further increase in the sound speed and the temperature coefficient may become slightly negative. For ablation therapy, an irreversible injury to tissue and a complete heart block occurs in the range of 48 to 50°C for a short period in accordance with the well-known Arrhenius equation. Using these two properties, we propose a potential tool to detect the moment when tissue damage occurs by using the reduced slope in the thermal strain curve as a function of heating time. We have illustrated the feasibility of this method initially using porcine myocardium in vitro. The method was further demonstrated in vivo, using a specially equipped ablation tip and an 11-MHz microlinear intracardiac echocardiography (ICE) array mounted on the tip of a catheter. The thermal strain curves showed a plateau, strongly suggesting that the temperature reached at least 50°C.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control 07/2011; 58(7):1406-17. · 1.80 Impact Factor
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Journal of cardiothoracic and vascular anesthesia 06/2011; 25(3):553-6. · 1.06 Impact Factor
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ABSTRACT: Definition of myocardial scars as identified by electroanatomic mapping is integral to catheter ablation of ventricular tachycardia (VT). Myocardial imaging can also identify scars prior to ablation. However, the relationship between imaging and voltage mapping is not well characterized.
The purpose of this study was to verify the anatomic location and heterogeneity of scars as obtained by electroanatomic mapping with contrast-enhanced MRI (CeMRI) and histopathology, and to characterize the distribution of late potentials in a chronic porcine infarct model.
In vivo 3-dimensional cardiac CeMRI was performed in 5 infarcted porcine hearts. High-density electroanatomic mapping was used to generate epicardial and endocardial voltage maps. Scar surface area and position on CeMRI were then correlated with voltage maps. Locations of late potentials were subsequently identified. These were classified according to their duration and fractionation. All hearts underwent histopathological examination after mapping.
The total dense scar surface area and location on CeMRI correlated to the total epicardial and endocardial surface scar on electroanatomic maps. Electroanatomic mapping (average of 1,532 ± 480 points per infarcted heart) showed that fractionated late potentials were more common in dense scars (<0.50 mV) as compared with border zone regions (0.51 to 1.5 mV), and were more commonly observed on the epicardium.
In vivo, CeMRI can identify areas of transmural and nontransmural dense scars. Fractionated late diastolic potentials are more common on the epicardium than the endocardium in dense scar. These findings have implications for catheter ablation of VT and for targeting the delivery of future therapies to scarred regions.
Heart rhythm: the official journal of the Heart Rhythm Society 02/2011; 8(7):1060-7. · 4.56 Impact Factor
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ABSTRACT: Late potential (LP) electrograms represent areas of slow conduction and are often sites critical to reentrant tachycardia circuits. The distribution of LPs within infarct scar is not known.
The purpose of this study was to delineate infarct heterogeneity using ultra high-density mapping and to determine the location of LPs with respect to scar architecture.
Detailed endocardial (n = 21) and epicardial (n = 8) ultra high-density mapping was performed to delineate the substrate for ventricular tachycardia (VT) in 21 patients with ischemic cardiomyopathy. LP was defined as a low-voltage electrogram (< 1.5 mV) with distinct onset after the QRS. Very late potentials (vLPs) were classified as LPs with onset > 100 ms after the QRS.
A mean of 787 ± 391 and 810 ± 375 points in the LV endocardium and epicardium were sampled. Multipolar mapping identified heterogeneous islets (HIs) with relatively preserved electrogram amplitudes (≥ 0.51 mv) within dense scar (8.5 ± 4.9/4.5 ± 2.6 HIs per endocardium/epicardium) in all patients. In maps on which putative VT isthmuses were identified (25/29), 57% of vLP were recorded in or adjacent to HI. An LP-targeted ablation strategy combined with pace mapping achieved acute success in all patients (complete success in 52% and partial success in 48%). After 15 ± 7 months, 65% of patients remained free of VT episodes.
Ultra high-density mapping with a multipolar catheter facilitates the delineation of heterogeneous scar architecture at higher resolution. Electrograms within and adjacent to HIs have a higher incidence of vLP, and these sites are frequently critical to reentry. These findings have important implications for substrate-based ablation strategies.
Heart rhythm: the official journal of the Heart Rhythm Society 12/2010; 7(12):1817-24. · 4.56 Impact Factor
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ABSTRACT: Prior chest surgery limits the ability to obtain epicardial access in patients referred for catheter ablation of ventricular tachycardia (VT).
The purpose of this study was to describe the utility of different surgical approaches to access the epicardium for VT ablation.
Clinical data of 14 patients with drug-refractory VT who underwent hybrid surgical epicardial access for catheter mapping and ablation in the electrophysiology lab were reviewed. Baseline patient and procedural characteristics including access, exposure, mapping techniques, and ablation were analyzed.
Of a total of 14 patients (age 63.2 ± 10.3 years), 11 had a subxiphoid window performed, and three patients underwent limited anterior thoracotomy to access the epicardium. The indication for surgical access was prior cardiac surgery (n = 12), previous failed epicardial access (n = 1), and ablation in close proximity to the coronary arteries and phrenic nerve (n = 1). Mapping in patients with subxiphoid surgical access was limited to the inferior and diaphragmatic surface of the heart extending posteriorly to the basal lateral wall. With limited anterior thoracotomy, access to the apex, anterior, and mid to apical anterolateral walls was obtained. In these regions, adhesions were more severe and repeat entry into the epicardial region at a different intercostal level was needed in two of three patients.
Surgical access with subxiphoid window and limited anterior thoracotomy in the electrophysiology lab is feasible and safe. The surgical approach can be tailored to the region of interest in the ventricle to be mapped and ablated.
Heart rhythm: the official journal of the Heart Rhythm Society 11/2010; 7(11):1635-43. · 4.56 Impact Factor
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ABSTRACT: Conduction abnormalities, commonly seen in systolic heart failure, lead to delayed activation of the myocardium as the electrical impulse spreads slowly without the aid of healthy conduction tissue. The resulting dyssynchronous ventricular contraction is mechanically less efficient, reducing systolic function and impairing diastolic filling. Simultaneous pacing of the right and left ventricles (i.e., biventricular pacing) reduces ventricular dyssynchronous contraction, overcoming these consequences of conduction delay. An important role for implantable rhythm-management devices providing cardiac resynchronization therapy has emerged in the optimization of ventricular function in heart failure. Long-term benefits in patient outcomes have been well established. With increasing use, understanding of cardiac resynchronization therapy devices and the principles behind the therapy are important for physicians providing perioperative and intensive care for patients with heart failure.
Anesthesia and analgesia 11/2010; 111(6):1353-61. · 3.08 Impact Factor
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Anesthesiology 10/2010; 113(4):765-6. · 5.36 Impact Factor
