Waveform optimization for internal atrial defibrillation: Effects of waveform rounding, phase duration, and voltage swing

The aim of this study was to compare the efficacy of internal atrial defibr illation by conventional truncated exponential biphasic waveforms with and without waveform rounding (1-2 phases) and to determine optimal duration fo r this novel double rounded waveform. A trial fibrillation, induced by rapi d electrical stimulation, was converted by internal shocks through defibril lation catheters (lateral right atrium and coronary sinus) in anesthetised sheep. Rounding the leading edges of the conventional biphasic waveform (Ve ntritex HVS-02; settings 100/-50 V, 150/-70 V, and 200/-100 V, n = 8) reduc ed delivered peak and trough voltages, currents, and energy (by greater tha n or equal to 21%, P < 0.001; for double (both phases) rounded) without dec reasing cardioversion success. At 100/-50 V the efficacy of single (first p hase) rounded (53<plus/minus>13%; mean +/- SEM) and double rounded (59 +/- 11%) shocks was similar to the conventional waveform (56 +/- 14%). Double r ounded waveform (phase durations 1-20 ms) efficacy was optimum at 6-10 ms p hase duration (100% success at 10-ms phase duration; 1.52 +/-0.04 J deliver ed energy, n = 6). Successful cardioversion by conventional, single rounded , and double rounded biphasic waveforms (duration 6 ms each phase), convent ional monophasic, rounded monophasic (duration 12 ms), and a damped sine wa veform correlated strongly with peak-to-trough voltage swing within the wav eform (r = 0.882; P < 0.01; n = 8). For internal atrial defibrillation, rou nding both phases of the conventional biphasic waveforms, the double rounde d waveform, permits similar efficacy to the conventional truncated exponent ial biphasic waveform at reduced peak voltage, current, and delivered energ y. Optimum phase duration is 6-10 ms (tested range 1-20 ms).