https://www.heartrhythmjournal.com/article/S1547-5271(04)00784-2/pdf

One conversion of ventricular fibrillation is adequate for implantable cardioverter-defibrillator implant: An analysis from the Low Energy Safety Study (LESS)

Defibrillation with Small Capacitance. Introduction: The size of current implantable cardioverter defibrillators (ICD) is still large in comparison to pacemakers and thus not convenient for pectoral implantation. One way to reduce ICD size is to defibrillate with smaller capacitors. A trade-off exists, however, since smaller capacitors may generate a lower maximum energy output.



Methods and Results: In a prospective randomized cross-over study, the step-down defibrillation threshold (DFT) of an experimental 90-μF biphasic waveform was compared to a standard 125-μF biphasic waveform. The 90-μF capacitor delivered the same energy faster and with a higher peak voltage but provided only a maximum energy output of 20 instead of 34 J. DFTs were determined intraoperatively in 30 patients randomized to receive either an endocardial (n = 15) or an endocardial-subcutaneous array (n = 15) defibrillation lead system. Independent of the lead system used, energy requirements did not differ at DFT for the experimental and the standard waveforms (10.3 ± 4.1 and 9.5 ± 4.9 J, respectively), but peak voltages were higher for the experimental waveform than for the standard waveform (411 ± 80 and 325 ± 81 V, respectively). For the experimental waveform the DFT was 10 J or less using an endocardial lead-alone system in 10 (67%) of 15 patients and in 12 (80%) of 15 patients using an endocardial-subcutaneous array lead system.



Conclusions: A shorter duration waveform delivered by smaller capacitors does not increase defibrillation energy requirements and might reduce device size. However, the smaller capacitance reduces the maximum energy output. If a 10-J safety margin between DFT and maximum energy output of the ICD is required, only a subgroup of patients will benefit from 90-μF ICDs with DFTs feasible using current defibrillation lead systems.

Internal defibrillation with smaller capacitors: a prospective randomized cross-over comparison of defibrillation efficacy obtained with 90-microF and 125-microF capacitors in humans.

The Low Energy Endotak Trial (LEET) was designed as a prospective, randomized, multicenter study to evaluate the efficacy and safety in nonthoracotomy cardioverter-defibrillator therapy with lower defibrillation energies compared to the conventional programming with devices set at maximum output. Between December 1993 and January 1996, 172 consecutive patients, undergoing implantation of a biphasic cardioverter-defibrillator with a single endocardial defibrillation lead system, were screened for study enrollment in 4 European study centers. Study inclusion criteria were defined as documented ventricular fibrillation, polymorphic ventricular tachycardia, or fast, hemodynamically unstable ventricular tachycardia, unresponsive to antitachycardia pacing and an augmented defibrillation threshold (DFT+) ≤ 15 Joules (J). Patients presenting slow, pace-terminable ventricular tachycardias were excluded. Patients were randomized into 2 study arms: (1) test group patients: the first-shock energy of the implanted devices was programmed at 2 × DFT+, the second to fifth shocks at maximum output (34 J); (2) control group patients: all shocks were programmed at 34 J. Ventricular fibrillation (VF) conversion tests (first shock energy DFT+; second shock 2 × DFT+) were performed in test group patients intraoperatively, during predischarge test, and after 12 months follow-up. In the control group patients, the arrhythmia conversion tests were performed with maximum device output (34 J). Spontaneous tachyarrhythmia episodes were classified by stored intracardiac electrogram analysis, and conversion rates were compared between the 2 study groups. Of the 172 screened patients, 162 (94%) met the inclusion criteria and were enrolled in the study. The mean DFT+ was 9.6 ± 3.2 J in the test group and 10.0 ± 3.5 J in the control group. The success rate for the test group for a repeated arrhythmia conversion test at DFT+ was 84.4% (157 of 186 induced VF episodes); the cumulative success rate for the first and the second shocks was 99.5% (185 of 186 induced episodes). In the control group, the first-shock conversion rate at 34 J was 98.8% (158 of 160 induced episodes). During a mean follow-up of 10 ± 7 months, the first-shock conversion rate for spontaneous arrhythmia episodes was 98.5% (65 of 66 episodes) in the test group patients and 92% (69 of 75 episodes) in control group patients (p >0.05). Analyzing the pooled data of spontaneous and induced arrhythmia episodes, there were no differences regarding the first shock conversion rate between the 2 groups (test group: 98.4%; control group: 96.6%; p >0.05). The overall mortality was 3%, equally distributed in both groups. The preliminary results of this study suggest that over a 1-year period, the “2 × DFT+” safety margin was equally effective as the margin provided by a 34-J device for conversion of induced and spontaneous tachyarrhythmia episodes. (Am J Cardiol 1996;78(suppl 5A):26–32)

Safety Margins: Lessons from the Low Energy Endotak Trial (LEET)

Objectives: The effect of implantable cardioverter/defibrillator (ICD) lead placement in the right ventricle (RV) on defibrillation efficacy has not been thoroughly investigated. Therefore, the goal of this combined experimental and clinical study was to evaluate the effect of a septal and a non-septal position of the right ventricular endocardial spring lead on defibrillation energy. Methods: In 12 isofluraneanaesthetized swine and subsequently in 8 patients who underwent ICD implantation, two different positions of the distal spring lead in the RV were investigated in randomized order: non-septal position (free wall of the RV) and septal position (interventricular septum). For each position, separate 50% probability determinations of energy (E 50), peak voltage (V50) and peak current (A50) were calculated using the three reversal up/down defibrillation procedure. The E 50 ,V 50 ,A 50 and impedance (I) were averaged and compared using the two-sided t-test for paired samples. Results: Both the experimental study and the clinical study demonstrated that placing the distal defibrillation lead near to the septum rather than near to the ventricular free wall resulted both in the swine and in the patients in significantly lower E50 -31.6%/ - 37.1%, V50 -16.1%/-20.9% and A50 -10.0%/ - 24.2%, respectively. Defibrillation impedances were significantly reduced only in the experimental study. Conclusions: Defibrillation efficacy depends on the position of the distal spring electrode in the RV. A septal position significantly reduces the energy requirements compared to a non-septal position. The decrease in energy requirements might be explained by an increase in current flow through the septum and the posterolateral wall of the left ventricle. © 1998 Elsevier Science B.V. All rights reserved

/pdf/effect-of-implantable-cardioverter-defibrillator-lead-49b8b2w6w9.pdf

Effect of implantable cardioverter/defibrillator lead placement in the right ventricle on defibrillation energy requirements. A combined experimental and clinical study.

The Low Energy Endotak Trial (LEET) was designed as a prospective, randomized, multicenter study to evaluate the efficacy and safety in nonthoracotomy cardioverter-defibrillator therapy with lower defibrillation energies compared to the conventional programming with devices set at maximum output. Between December 1993 and January 1996, 172 consecutive patients, undergoing implantation of a biphasic cardioverter-defibrillator with a single endocardial defibrillation lead system, were screened for study enrollment in 4 European study centers. Study inclusion criteria were defined as documented ventricular fibrillation, polymorphic ventricular tachycardia, or fast, hemodynamically unstable ventricular tachycardia, unresponsive to antitochycardia pacing and an augmented defibrillation threshold (DFT+) ≤15 Joules (J). Patients presenting slow, pace-terminable ventricular tachycardias were excluded. Patients were randomized into 2 study arms : (1) test group patients: the first-shock energy of the implanted devices was programmed at 2 x DFT+, the second to fifth shocks at maximum output (34 J) ; (2) control group patients: all shocks were programmed at 34 J. Ventricular fibrillation (VF) conversion tests (first shock energy DFT+ ; second shock 2 x DFT+) were performed in test group patients intraoperatively, during predischarge test, and after 12 months follow-up. In the control group patients, the arrhythmia conversion tests were performed with maximum device output (34 J). Spontaneous tachyarrhythmia episodes were classified by stored intracardiac electrogram analysis, and conversion rates were compared between the 2 study groups. Of the 172 screened patients, 162 (94%) met the inclusion criteria and were enrolled in the study. the mean DFT+ was 9.6 ± 3.2 J in the test group and 10.0 ± 3.5 J in the control group. The success rate for the test group for a repeated arrhythmia conversion test at DFT+ was 84.4% (157 of 186 induced VF episodes) ; the cumulative success rate for the first, and the second shocks was 99. 5% (185 of 186 induced episodes). In the control group, the first-shock conversion rate at 34 J was 98.8% (158 of 160 induced episodes). During a mean follow-up of 10 ± 7 months, the first-shock conversion rate for spontaneous arrhythmia episodes was 98.5% (65 of 66 episodes) in the test group patients and 92% (69 of 75 episodes) in control group patients (p >0.05). Analyzing the pooled data of spontaneous and induced arrhythmia episodes, there were no differences regarding the first shock conversion rate between the 2 groups (test group : 98.4% ; control group : 96.6% ; p >0.05). The overall mortality was 3%, equally distributed in both groups. The preliminary results of this study suggest that over a 1-year period, the 2 x DFT+ safety margin was equally effective as the margin provided by a 34-J device for conversion of induced and spontaneous tachyarrhythmia episodes.

Safety margins : Lessons from the low energy endotak trial (LEET). Discussion

Mapping And Pacing Of Atrial Fibrillation Mechanisms Of Defibrillation Electrode Configurations For Internal Atrial Defibrillation Current Distribution Around Defibrillation Electrodes: Computer Modelling Approach Profiles Of High-Risk Patients Reflections On Guidelines For The Use Of Implantable Pacemaker-Cardioverter-Defibrillators Which ICD For Which Patient? Surgical Aspects Of CD Implantation Influence Of Electrode Position Of Defibrillation Threshold Implantable Transvenous Cardioverter-Defibrillator With Pectoral Subcutaneous Patch Relationship Between Acute Defibrillation Threshold And Therapy Outcome Chronic Clinical Results Of Nonthoracotomy Implantable Cardioverter-Defibrillator Therapy Treatment Of Ventricular Tachycardia With Antitachycardia Pacing In Patients With An Implantable Cardioverter-Defibrillator The Use of Antiarrhythmic Drugs In ICD Patients Transtelephonic ICD Monitoring U-CARE: Unexplained Cardiac Arrest Registry Of Europe Defibrillator Implantation For Patients With Primary Electrical Disease Miracles: A Study Of Prevention Of Sudden Cardiac Death In High-Risk Patients By Defibrillator Implantation Early After AMI The Future Of Arrhythmia Surgery Principles And Techniques Of Catheter Ablation Treatment Of "Mahaim" Tachycardias By Radiofrequency Catheter Ablation Radiofrequency Ablation Of The Slow Pathway In AV Nodal Reentrant Tachycardia: Electrogram Patterns At The Successful Site Radiation Exposure During RF-Ablation Of Accessory Pathways

Transvenous defibrillation and radiofrequency ablation

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Transvenous defibrillation and radiofrequency ablation