BIPHASIC DEFIBRILLATION USING A SINGLE CAPACITOR WITH LARGE CAPACITANCE - REDUCTION OF PEAK VOLTAGES AND ICD DEVICE SIZE

The volume of current implantable cardioverter defibrillators (ICD) is not convenient for pectoral implantation. One way to reduce the size of the pulse generator is to find a more effective defibrillation puls e waveform generated from smaller volume capacitors. In a prospective randomized crossover study we compared the step-down defibrillation th reshold (DFT) of a standard biphasic waveform (STD), delivered by two 250-mu F capacitors connected in series with an 80% tilt, to an experi mental biphasic waveform delivered by a single 450-mu F capacitor with a 60% tilt. The experimental waveform delivered the same energy with a lower peak voltage and a longer duration (LVLD). Intraoperatively, i n 25 patients receiving endocardial (n = 12) or endocardial-subcutaneo us army (n = 13) defibrillation leads, the DFT was determined for both waveforms. Energy requirements did not differ at DFT for the STD and LVLD waveforms with the low impedance (32 +/- 4 Ohm) endocardial-subcu taneous array defibrillation lead system (6.4 +/- 4.4 J and 5.9 +/- 4. 2 J respectively) or increased slightly (P = 0.06) with the higher imp edance (42 +/- 4 Ohm) endocardial lead system (10.4 +/- 4.6 J and 12.7 +/- 5.7 J, respectively). However, the voltage needed at DFT was one- third lower with the LVLD waveform than with the STD waveform for both lead systems (256 +/- 85 V vs 154 +/- 51 V and 348 +/- 76 V vs 232 +/ - 54 V, respectively). Thus, a single capacitor with a large capacitan ce can generate a defibrillation pulse with a substantial lower peak v oltage requirement without significantly increasing the energy require ments. The volume reduction in using a single capacitor can decrease I CD device size.