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Douglas L. Jones - One of the best experts on this subject based on the ideXlab platform.
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Combination biphasic waveform plus sequential pulse Defibrillation improves Defibrillation efficacy of a nonthoracotomy lead system
Journal of the American College of Cardiology, 1994Co-Authors: Derek V. Exner, Douglas L. Jones, George J. Klein, Raymond Yee, Rahul MehraAbstract:We hypothesized that combining biphasic waveform and sequential pulse Defibrillation techniques would lower the Defibrillation threshold of a nonthoracotomy lead system in humans below that obtained with biphasic or sequential pulse Defibrillation alone. Previous studies have shown that sequential pulse monophasic shocks and biphasic waveform shocks are more effective than single monophasic shocks for ventricular Defibrillation. Thirteen patients aged 48 to 71 years undergoing nonthoracotomy Defibrillation lead testing participated in the study. Transvenous electrodes were positioned in the right ventricular apex, superior vena cava and coronary sinus. A cutaneous patch electrode was placed on the left chest wall. All electrodes were connected to an external defibrillator. In random order, Defibrillation threshold measurements were made for biphasic Defibrillation alone, sequential Defibrillation alone and combined biphasic plus sequential Defibrillation. The mean Defibrillation threshold-delivered energy was 18.0 +/- 11.9 J for biphasic Defibrillation and 16.3 +/- 9.0 J for sequential Defibrillation. Biphasic plus sequential Defibrillation significantly reduced the threshold energy to 10.2 +/- 5.3 J (p < 0.001). Threshold peak voltage and current values showed corresponding reductions. The combined waveform resulted in a greater reduction in Defibrillation threshold in patients with threshold energies > 18 J versus those with threshold values < or = 18 J for sequential (p = 0.001) or biphasic (p < 0.01) waveform alone. The nonthoracotomy lead implantation rate was improved from 62% with each of the single techniques (biphasic waveform or sequential pulse Defibrillation) to 85% with the combined waveform. Adding biphasic waveform to sequential pulse Defibrillation significantly reduced the Defibrillation threshold compared with either technique alone, and nonthoracotomy lead system implantation can be enhanced by this combined technique.
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Defibrillation shocks produce different effects on purkinje fibers and ventricular muscle implications for successful Defibrillation refibrillation and postshock arrhythmia
Journal of the American College of Cardiology, 1993Co-Authors: Huagui G Li, Douglas L. Jones, George KleinAbstract:Objectives. To understand the mechanisms of postDefibrillation arrhythmias and failed Defibrillation, we studied the cellular effects of high voltage shocks on different cardiomyocytes in the dog. Background. The causes of postDefibrillation arrhythmias and unsuccessful Defibrillation are not clear. Methods. High voltage shocks with voltage differentials of 9.3 to 97.6 V/cm were delivered to isolated canine papillary muscles with attached Purkinje fibers. Transmembrane potentials were recorded simultaneously from the Purkinje fiber and the ventricular muscle using standard microelectrode techniques. Results. After delivery of high voltage shocks, significant depolarization and rapid firing were observed in Purkinje fibers. The maximal rate of the rapid firing in the Purkinje fibers correlated with shock intensity (r = 0.69, p < 0.05). In contrast, in ventricular muscle, only slight depolarization and a transient refractory state were observed after the shock. The incidence of the refractory state was correlated with both the shock intensity and the rate of the rapid firing in the Purkinje fiber (r = 0.89 and 0.74, p < 0.01 and 0.05, respectively). Propranolol at a concentration sufficient for complete beta-blockade (1 mg/liter) did not change the tissue response to shocks but suppressed or abolished the shock-induced rapid firing of Purkinje fibers at a higher concentration (3 mg/liter). Blockade of the slow calcium channel with verapamil (400 μg/dl) did not alter the responsiveness of the preparation to shocks. Conclusion. These results indicate that high voltage shocks induce different responses in Purkinje fibers and ventricular muscle. The shock-induced rapid firing in the Purkinje fiber may contribute to postshock arrhythmias and possibly refibrillation in some cases. The shock-induced transient refractory state in the ventricular muscle may prevent the ventricle from responding to the rapid firing and thus may decrease the incidence of postshock arrhythmias.
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Effects of lidocaine and verapamil on Defibrillation in humans.
Journal of electrocardiology, 1991Co-Authors: Douglas L. Jones, George J. Klein, Gerard M. Guiraudon, Raymond Yee, James E. Brown, Arjun D. SharmaAbstract:Patients with automatic defibrillators frequently require chronic antiarrhythmic drug therapy or receive acute therapy with the onset of symptoms. The effects on energy requirements for Defibrillation of lidocaine hydrochloride and verapamil hydrochloride, two commonly used antiarrhythmic agents, were examined in 20 successive patients undergoing corrective arrhythmia surgery. The minimum energy requirement for ventricular Defibrillation before and 5 minutes after the administration of 150 mg of lidocaine intravenously (n = 8), or 10 minutes after 10 mg of verapamil intravenously (n = 12), were determined. Each patient was assigned to receive either verapamil or lidocaine. Three mesh coil defibrillating electrodes (Medtronic 6891, 6892) were sutured to the epicardium of the right and left ventricles. Ventricular fibrillation was induced using alternating current. After a minimum of 10 seconds of fibrillation, the minimum energy for Defibrillation was established using sequential pulse Defibrillation. The preselected drug was then infused and the ventricular Defibrillation energy was again determined after 5 or 10 minutes circulation time. Lidocaine did not alter the minimum energy for Defibrillation (3.0 +/- 1.4 J vs. 3.0 +/- 1.8 J, mean +/- SD), despite plasma levels of lidocaine that averaged 13.2 +/- 1.9 mumol/l. In contrast, verapamil significantly increased (3.9 +/- 2.2 J vs. 6.5 +/- 2.9 J) the minimum energy necessary for Defibrillation. The difference in Defibrillation energy was significantly correlated to the fall in systolic blood pressure induced by verapamil administration (r = 0.72). These data reinforce the necessity for determining efficacy of Defibrillation when medication changes are instituted. Verapamil should be used with caution in patients with automatic defibrillators and marginal Defibrillation threshold.
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Defibrillation efficacy. Comparison of Defibrillation threshold versus dose-response curve determination.
Circulation research, 1991Co-Authors: Douglas L. Jones, W D Irish, George J. KleinAbstract:When an automatic defibrillator is implanted, it is essential to determine the efficacy of the defibrillating system accurately, while balancing the need to keep the number of fibrillation episodes to a minimum. Two methods have evolved to assess Defibrillation efficacy: 1) the "Defibrillation threshold," which requires few ventricular fibrillation episodes, and 2) the "dose-response curve," which requires many ventricular fibrillation episodes and relates percent success to energy. The purpose of this study was to compare these two methods directly. Twenty open-chest anesthetized pigs had triplicate Defibrillation threshold determinations. To produce a dose-response curve, six shocks then were delivered at 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0 times the mean Defibrillation threshold, in a balanced randomized order, during separate episodes of ventricular fibrillation. The data were fitted by logistic regression, conversions of the logistic regression, and a saturable exponential and nonsaturable growth exponential. A comparison was made of the mean Defibrillation threshold and the 50% point on the dose-response curve (ED50) for each model, for each animal. In addition, the reliability of each measure was assessed by comparing the coefficients of variation. There was no statistical difference between the group Defibrillation threshold (6.6 +/- 0.5 J) and group ED50 values (ED50 range of the models, 5.7 +/- 1.9 to 7.0 +/- 0.9 J). However, the variability about the Defibrillation threshold was less than that of the ED50 values for all mathematical models except the true logistic equation, which was virtually the same.(ABSTRACT TRUNCATED AT 250 WORDS)
George J. Klein - One of the best experts on this subject based on the ideXlab platform.
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Combination biphasic waveform plus sequential pulse Defibrillation improves Defibrillation efficacy of a nonthoracotomy lead system
Journal of the American College of Cardiology, 1994Co-Authors: Derek V. Exner, Douglas L. Jones, George J. Klein, Raymond Yee, Rahul MehraAbstract:We hypothesized that combining biphasic waveform and sequential pulse Defibrillation techniques would lower the Defibrillation threshold of a nonthoracotomy lead system in humans below that obtained with biphasic or sequential pulse Defibrillation alone. Previous studies have shown that sequential pulse monophasic shocks and biphasic waveform shocks are more effective than single monophasic shocks for ventricular Defibrillation. Thirteen patients aged 48 to 71 years undergoing nonthoracotomy Defibrillation lead testing participated in the study. Transvenous electrodes were positioned in the right ventricular apex, superior vena cava and coronary sinus. A cutaneous patch electrode was placed on the left chest wall. All electrodes were connected to an external defibrillator. In random order, Defibrillation threshold measurements were made for biphasic Defibrillation alone, sequential Defibrillation alone and combined biphasic plus sequential Defibrillation. The mean Defibrillation threshold-delivered energy was 18.0 +/- 11.9 J for biphasic Defibrillation and 16.3 +/- 9.0 J for sequential Defibrillation. Biphasic plus sequential Defibrillation significantly reduced the threshold energy to 10.2 +/- 5.3 J (p < 0.001). Threshold peak voltage and current values showed corresponding reductions. The combined waveform resulted in a greater reduction in Defibrillation threshold in patients with threshold energies > 18 J versus those with threshold values < or = 18 J for sequential (p = 0.001) or biphasic (p < 0.01) waveform alone. The nonthoracotomy lead implantation rate was improved from 62% with each of the single techniques (biphasic waveform or sequential pulse Defibrillation) to 85% with the combined waveform. Adding biphasic waveform to sequential pulse Defibrillation significantly reduced the Defibrillation threshold compared with either technique alone, and nonthoracotomy lead system implantation can be enhanced by this combined technique.
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Effects of lidocaine and verapamil on Defibrillation in humans.
Journal of electrocardiology, 1991Co-Authors: Douglas L. Jones, George J. Klein, Gerard M. Guiraudon, Raymond Yee, James E. Brown, Arjun D. SharmaAbstract:Patients with automatic defibrillators frequently require chronic antiarrhythmic drug therapy or receive acute therapy with the onset of symptoms. The effects on energy requirements for Defibrillation of lidocaine hydrochloride and verapamil hydrochloride, two commonly used antiarrhythmic agents, were examined in 20 successive patients undergoing corrective arrhythmia surgery. The minimum energy requirement for ventricular Defibrillation before and 5 minutes after the administration of 150 mg of lidocaine intravenously (n = 8), or 10 minutes after 10 mg of verapamil intravenously (n = 12), were determined. Each patient was assigned to receive either verapamil or lidocaine. Three mesh coil defibrillating electrodes (Medtronic 6891, 6892) were sutured to the epicardium of the right and left ventricles. Ventricular fibrillation was induced using alternating current. After a minimum of 10 seconds of fibrillation, the minimum energy for Defibrillation was established using sequential pulse Defibrillation. The preselected drug was then infused and the ventricular Defibrillation energy was again determined after 5 or 10 minutes circulation time. Lidocaine did not alter the minimum energy for Defibrillation (3.0 +/- 1.4 J vs. 3.0 +/- 1.8 J, mean +/- SD), despite plasma levels of lidocaine that averaged 13.2 +/- 1.9 mumol/l. In contrast, verapamil significantly increased (3.9 +/- 2.2 J vs. 6.5 +/- 2.9 J) the minimum energy necessary for Defibrillation. The difference in Defibrillation energy was significantly correlated to the fall in systolic blood pressure induced by verapamil administration (r = 0.72). These data reinforce the necessity for determining efficacy of Defibrillation when medication changes are instituted. Verapamil should be used with caution in patients with automatic defibrillators and marginal Defibrillation threshold.
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Defibrillation efficacy. Comparison of Defibrillation threshold versus dose-response curve determination.
Circulation research, 1991Co-Authors: Douglas L. Jones, W D Irish, George J. KleinAbstract:When an automatic defibrillator is implanted, it is essential to determine the efficacy of the defibrillating system accurately, while balancing the need to keep the number of fibrillation episodes to a minimum. Two methods have evolved to assess Defibrillation efficacy: 1) the "Defibrillation threshold," which requires few ventricular fibrillation episodes, and 2) the "dose-response curve," which requires many ventricular fibrillation episodes and relates percent success to energy. The purpose of this study was to compare these two methods directly. Twenty open-chest anesthetized pigs had triplicate Defibrillation threshold determinations. To produce a dose-response curve, six shocks then were delivered at 0.5, 0.75, 1.0, 1.25, 1.5, and 2.0 times the mean Defibrillation threshold, in a balanced randomized order, during separate episodes of ventricular fibrillation. The data were fitted by logistic regression, conversions of the logistic regression, and a saturable exponential and nonsaturable growth exponential. A comparison was made of the mean Defibrillation threshold and the 50% point on the dose-response curve (ED50) for each model, for each animal. In addition, the reliability of each measure was assessed by comparing the coefficients of variation. There was no statistical difference between the group Defibrillation threshold (6.6 +/- 0.5 J) and group ED50 values (ED50 range of the models, 5.7 +/- 1.9 to 7.0 +/- 0.9 J). However, the variability about the Defibrillation threshold was less than that of the ED50 values for all mathematical models except the true logistic equation, which was virtually the same.(ABSTRACT TRUNCATED AT 250 WORDS)
Rahul Mehra - One of the best experts on this subject based on the ideXlab platform.
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Combination biphasic waveform plus sequential pulse Defibrillation improves Defibrillation efficacy of a nonthoracotomy lead system
Journal of the American College of Cardiology, 1994Co-Authors: Derek V. Exner, Douglas L. Jones, George J. Klein, Raymond Yee, Rahul MehraAbstract:We hypothesized that combining biphasic waveform and sequential pulse Defibrillation techniques would lower the Defibrillation threshold of a nonthoracotomy lead system in humans below that obtained with biphasic or sequential pulse Defibrillation alone. Previous studies have shown that sequential pulse monophasic shocks and biphasic waveform shocks are more effective than single monophasic shocks for ventricular Defibrillation. Thirteen patients aged 48 to 71 years undergoing nonthoracotomy Defibrillation lead testing participated in the study. Transvenous electrodes were positioned in the right ventricular apex, superior vena cava and coronary sinus. A cutaneous patch electrode was placed on the left chest wall. All electrodes were connected to an external defibrillator. In random order, Defibrillation threshold measurements were made for biphasic Defibrillation alone, sequential Defibrillation alone and combined biphasic plus sequential Defibrillation. The mean Defibrillation threshold-delivered energy was 18.0 +/- 11.9 J for biphasic Defibrillation and 16.3 +/- 9.0 J for sequential Defibrillation. Biphasic plus sequential Defibrillation significantly reduced the threshold energy to 10.2 +/- 5.3 J (p < 0.001). Threshold peak voltage and current values showed corresponding reductions. The combined waveform resulted in a greater reduction in Defibrillation threshold in patients with threshold energies > 18 J versus those with threshold values < or = 18 J for sequential (p = 0.001) or biphasic (p < 0.01) waveform alone. The nonthoracotomy lead implantation rate was improved from 62% with each of the single techniques (biphasic waveform or sequential pulse Defibrillation) to 85% with the combined waveform. Adding biphasic waveform to sequential pulse Defibrillation significantly reduced the Defibrillation threshold compared with either technique alone, and nonthoracotomy lead system implantation can be enhanced by this combined technique.
Gust H. Bardy - One of the best experts on this subject based on the ideXlab platform.
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Clinical predictors of the Defibrillation threshold with the unipolar implantable Defibrillation system
Journal of the American College of Cardiology, 1995Co-Authors: Merritt H. Raitt, George Johnson, G. Lee Dolack, Jeanne E. Poole, Peter J. Kudenchuk, Gust H. BardyAbstract:The purpose of this study was to determine the relation between clinical variables and the Defibrillation threshold by using a standardized testing protocol and a uniform implantable defibrillator system. Past studied have not revealed useful correlations between clinical variables and the energy required to terminate ventricular fibrillation. Most of these studies did not use a uniform implantable defibrillator system or a standardized protocol to measure the Defibrillation threshold and, thus, did not control for the influence of these technical influences. We postulated that defibrillator and Defibrillation threshold measurement-based sources of variability overshadowed important clinical predictors. The Defibrillation threshold was measured by using a standardized protocol in 101 consecutive patients. We used a transvenous unipolar pectoral Defibrillation system that employed a single endocardial right ventricular Defibrillation coil as the anode and the shell of an 80-cm3 pulse generator as the cathode to deliver a 65% tilt biphasic pulse. Several clinical variables were found to be significantly associated with the Defibrillation threshold: patient gender, height, weight, body surface area, heart rate at rest, QRS and corrected QT (QTc) intervals, left ventricular mass and several measures of heart and chest size by chest roentgenogram. None of these variables had a correlation coefficient > 0.45 with the Defibrillation threshold. On multivariate analysis, left ventricular mass and heart rate at rest were the only independent predictors of the Defibrillation threshold and explained only 25% of the observed variability. Despite the use of a uniform transvenous Defibrillation system and a standardized protocol to measure the Defibrillation threshold, no clinically relevant correlation was found between clinical variables and the Defibrillation threshold. The Defibrillation threshold is probably a function of a complex interaction of anatomic, physiologic and cellular variables that are not adequately represented by easily obtainable clinical information. It is probably not possible to predict Defibrillation outcome from standard clinical variables.
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A Prospective Randomized Comparison in Humans of 90‐μF and 120‐μF Biphasic Pulse Defibrillation Using a Unipolar Defibrillation System
Journal of cardiovascular electrophysiology, 1995Co-Authors: Jeanne E. Poole, George Johnson, Peter J. Kudenchuk, G L Dolack, Gregory K. Jones, Paul Degroot, Gust H. BardyAbstract:Capacitance is known to influence Defibrillation. Optimal biphasic waveform capacitance for transvenous unipolar Defibrillation systems in man is currently being defined. In an effort to improve Defibrillation efficacy, we examined the relative Defibrillation efficacy of a 65% tilt biphasic pulse from a 90-mu F capacitor compared to a 65% tilt biphasic pulse from a 120-mu F capacitor in a prospective, randomized fashion in 16 consecutive cardiac arrest survivors undergoing defibrillator surgery. The transvenous unipolar pectoral Defibrillation system uses a single endocardial RV anodal Defibrillation coil and the shell of an 80-cc volume (88 cm2 surface area) pulse generator (Medtronic Model 7219C PCD "active CAN") as the cathode for the first phase of the biphasic shock: RV+ --> CAN-. Defibrillation thresholds for each capacitance were determined prospectively in a randomized fashion. The Defibrillation threshold results for the 90-mu F capacitance were: leading edge voltage 383 +/- 132 V; stored energy 7.4 +/- 5.0 J; and resistance 57 +/- 10 omega. The results for the 120-mu F capacitance were: leading edge voltage 315 +/- 93 V (P = 0.002); stored energy 6.5 +/- 3.7 J (P = 0.21); and resistance 57.0 +/- 11 omega (P = 0.87). We conclude that 90-mu F, 65% tilt biphasic pulses used with unipolar pectoral Defibrillation systems have equivalent stored energy Defibrillation efficacy compared to 120-mu F, 65% tilt pulses. Use of lower capacitance is possible in present implantable defibrillators without compromising Defibrillation.
Fred Morady - One of the best experts on this subject based on the ideXlab platform.
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A Prospective Evaluation of Two Defibrillation Safety Margin Techniques in Patients with Low Defibrillation Energy Requirements
Journal of cardiovascular electrophysiology, 1998Co-Authors: S. Adam Strickberger, K. Ching Man, Joseph Souza, Adam Zivin, Raul Weiss, Bradley P. Knight, Rajiva Goyal, Emile G. Daoud, Fred MoradyAbstract:Low-Energy Defibrillation. Introduction: In patients undergoing defibrillator implantation, an appropriate Defibrillation safety margin has been considered to be either 10 J or an energy equal to the Defibrillation energy requirement. However, a previous clinical report suggested that a larger safety margin may be required in patients with a low Defibrillation energy requirement. Therefore, the purpose of this prospective study was to compare the Defibrillation efficacy of the two safety margin techniques in patients with a low Defibrillation energy requirement. Methods and Results: Sixty patients who underwent implantation of a defibrillator and who had a low Defibrillation energy requirement (≤ 6 J) underwent six separate inductions of ventricular fibrillation, at least 5 minutes apart. For each of the first three inductions of ventricular fibrillation, the first two shocks were equal to either the Defibrillation energy requirement plus 10 J (14.6 ± 1.0 J), or to twice the Defibrillation energy requirement (9.9 ± 2.3 J). The alternate technique was used for the subsequent three inductions of ventricular fibrillation. For each induction of ventricular fibrillation, the first shock success rate was 99.5%± 4.3% for shocks using the Defibrillation energy requirement plus 10 J, compared to 95.0%± 17.2% for shocks at twice the Defibrillation energy requirement (P = 0.02). The charge time (P < 0.0001) and the total duration of ventricular fibrillation (P < 0.0001) were each approximately 1 second longer with the Defibrillation energy requirement plus 10 J technique. Conclusion: This study is the first to compare prospectively the Defibrillation efficacy of two Defibrillation safety margins. In patients with a Defibrillation energy requirement ≤ 6 J, a higher rate of successful Defibrillation is achieved with a safety margin of 10 J than with a safety margin equal to the Defibrillation energy requirement.
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Randomized comparison of a 90 uF capacitor three-electrode Defibrillation system with a 125 uF two-electrode Defibrillation system.
Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing, 1998Co-Authors: Marwan Bahu, K. Ching Man, Raul Weiss, Bradley P. Knight, Rajiva Goyal, Emile G. Daoud, Fred Morady, Stephen J. Hahn, S. Adam StrickbergerAbstract:Introduction: A variety of factors, including the number of Defibrillation electrodes and shocking capacitance, may influence the Defibrillation efficacy of an implantable defibrillator system. Therefore, the purpose of this study was to compare the Defibrillation energy requirement using a 125 uF two-electrode Defibrillation system and a 90 uF three-electrode Defibrillation system.
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Probability of Successful Defibrillation at Multiples of the Defibrillation Energy Requirement in Patients With an Implantable Defibrillator
Circulation, 1997Co-Authors: S. Adam Strickberger, K. Ching Man, Raul Weiss, Bradley P. Knight, Rajiva Goyal, Emile G. Daoud, Marwan Bahu, Theresa Davidson, Frank Bogun, Fred MoradyAbstract:Background The probability of successful Defibrillation has been determined in normal animals but not in patients undergoing defibrillator implantation. Therefore, the purpose of this prospective study was to determine the probability of successful Defibrillation in humans on the basis of a step-down Defibrillation energy requirement. Methods and Results Fifty-three consecutive patients underwent five separate inductions of ventricular fibrillation after the Defibrillation energy requirement was determined with the use of small decrements and a step-down protocol (20, 15, 12, 10, 8, 6, 5, 4, 3, 2, 1, and 0.8 J). The first shock energy for Defibrillation was either 1.0, 1.3, 1.5, 1.7, or 2.0 times the Defibrillation energy requirement, and the likelihoods of successful Defibrillation were 70±27%, 84±12%, 86±25%, 80±29%, and 88±32%, respectively (P=.03). The frequencies of uniformly successful Defibrillation (5 of 5 Defibrillation attempts) were 30%, 27%, 60%, 64%, and 73%, respectively (P=.01). Seven patie...
