Large capacitor defibrillation waveform reduces peak voltages without increasing energies.
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)
Hahn
S J
SJ
Cardiac Pacemakers, Inc., St. Paul, Minnesota 55112.
Heil
J E
JE
Lang
D J
DJ
D000818:Animals; D017147:Defibrillators, Implantable; D004553:Electric Conductivity; D004554:Electric Countershock / Q000379:methods; D004567:Electrodes, Implanted; D004699:Endocardium; D004867:Equipment Design; D005260:Female; D013552:Swine; D014693:Ventricular Fibrillation / Q000628:therapy*