Clinical evaluation of defibrillation efficacy with a new single-capacitorbiphasic waveform in patients undergoing implantation of an implantable cardioverter defibrillator

Aims Improvements in the size and shape of implantable cardioverter defibri llators (ICDs) might be obtained by using one capacitor instead of the seri es connection of two capacitors traditionally used in ICDs. The aim of this study was to determine whether a biphasic waveform delivered from a single 336 muF capacitor had the same defibrillation efficacy as a standard bipha sic waveform. Methods and Results Randomized. paired defibrillation threshold testing was acutely performed in 54 patients undergoing ICD implantation. A standard 1 40 muF 80% tilt biphasic waveform (two 280 muF capacitors connected in seri es) was compared with an experimental biphasic waveform delivered from a si ngle 336 muF capacitor at either 60% tilt (33 patients) or 80% tilt (21 pat ients). All waveforms had a 60/40 phase1/phase2 duration ratio. Compared wi th the standard waveform, the 60% tilt experimental waveform had a lower de livered energy (6.7 +/- 2.8 vs 7.9 +/- 3.3 joules, P < 0.02), lower peak vo ltage (218 +/- 43 vs 333 +/- 68 V, P < 0.01), and a slightly longer pulse d uration (13.4 +/- 1.4 vs 10.7 +/- 1.1 ms, P < 0-01). Conversely, the 80% ti lt experimental waveform had a higher delivered energy (9.1 +/- 3.5 vs 6.3 +/- 2.4 joules, P < 0.01), a lower peak voltage (234 +/- 44 vs 302 +/- 51 V , P < 0.01) and a much longer pulse duration (25.7 +/- 2.5 vs 11.3 +/- 1 ms , P < 0.01). Conclusion Waveforms delivered from a large capacitance are feasible but re quire a lower tilt. This technique may allow smaller. thinner ICDs without jeopardizing defibrillation success. (C) 2001 The European Society of Cardi ology.