This study tested the hypothesis that increasing capacitance would allow a reduction in ICD size without reducing the deliverable energy. For example, the volume of a single 450 microF capacitor (390 V peak) is 1/3 less than that of two 250 microF capacitors (780 V), but it can store equivalent amounts of energy.
Methods: Endocardial defibrillation electrodes (3.4 cm) were positioned in the RV apex and at the RA/SVC junction in six mixed-breed, isoflurane anesthetized pigs (41 +/- 3 kg). Three 17-cm ribbon wires were positioned subcutaneously on the left lateral chest (SQArray). Two CPI VENTAK ECDs were equipped to deliver 60/40 biphasic waveforms using either 125 microF (STD) or 500 microF (LD) of capacitance. A 15 shock up/down protocol was used to determine the 50% probability of success levels for each waveform in each animal. Shocks were delivered from RV(-)-->SVC + SQArray(+) in random order. Results were compared using paired Student's t-tests and are reported as mean +/- SE.
Results: The 500 microF, long duration waveform reduced peak voltage 41% (374 +/- 18 V [STD] vs 219 +/- 14 V [LD], P < 0.001) and reduced peak current 38% (11.0 +/- 1.1 A [STD] vs 6.8 +/- 0.6 A [LD], P < 0.001) but did not significantly change the delivered energy (12.4 +/- 1.3 J [STD] vs 13.4 +/- 1.0 J [LD]). Durations increased from 10.0 +/- 0.2 to 17.6 +/- 0.5 msec (P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)