Optimal method to achieve consistently low defibrillation energy requirements

Reduction of the defibrillation energy requirement offers the opportunity to decrease implantable cardioverter defibrillator (ICD) size and to increase device longevity. Therefore, the purpose of this prospective study was to obtain confirmed defibrillation thresholds (DFTs) of < or = 15 J in each patient with an endocardial dual-coil lead system incorporating an active pectoral pulse generator (TRIAD lead system: RV- --> SVC+ + CAN+). According to our previous clinical and experimental studies, we tried to lower DFTs that were > 15 J by repositioning the distal coil of the endocardial lead system in the right ventricle. A total of 190 consecutive patients requiring ICDs for ventricular fibrillation and/or recurrent ventricular tachycardia were investigated at the time of ICD implantation (42 women, 148 men; mean age 61.9 +/- 12.0 years; mean left ventricular ejection fraction 42.7 +/- 16.6%). Coronary artery disease was present in 139 patients; nonischemic dilated cardiomyopathy in 34 patients; and other etiologies in 17 patients; 47 patients had undergone previous cardiac surgery. Regardless of optimal pacing and sensing parameters, for patients having DFTs > 15, we repositioned the distal coil of the endocardial lead system toward the intraventricular septum to include this part of both ventricles within the electrical defibrillating field. In 177 of 190 patients, induced ventricular fibrillation was successfully terminated with < or = 15 J (group I) using the initial lead position. Repositioning of the endocardial lead was necessary in 13 patients whose DFT(plus) (DFT(plus) = second additional success at lowest energy level) were > 15 J (group II). In all patients, repositioning was successful within a 15 J energy level (100% success). The mean DFT(plus) was 7.3 +/- 3.5 J (group I) and 11.0 +/- 4.5 J (group II; p<0.005). The mean DFT(plus) of all patients enrolled in the study was 7.6 +/- 3.7 J (range: 2 to 15 J). In 87% of all patients, DFT(plus) of < or = 10 J was achieved. Repositioning of the endocardial lead in the right ventricle is a simple and effective method to reduce intraoperative high DFTs. As a result of this procedure, ICDs with a 20 J output should be sufficient for the vast majority (87%) of our patients. Furthermore, we were able to avoid additional subcutaneous or epicardial electrodes in all patients.