TRUNCATED EXPONENTIAL VERSUS DAMPED SINUSOIDAL WAVE-FORM SHOCKS FOR TRANSTHORACIC DEFIBRILLATION

Currently available transthoracic defibrillators use either a damped s inusoidal or truncated exponential (TE) waveform. Truncated exponentia l waveforms deliver a long pulse if the transthoraic impedance is high ; it has been suggested that such a long pulse may be less effective f or defibrillation. Our objective was to compare the ability of damped sinusoidal (DS) waveform shocks versus TE waveform shocks to terminate ventricular fibrillation (VF) and achieve survival from witnessed car diac arrest. We retrospectively reviewed field-recorded electrocardiog rams from 86 patients with witnessed VF, treated by prehospital person nel equipped with DS or TE waveform defibrillators. forty-four patient s received 130 shocks from TE defibrillators; 42 patients received 108 shocks from DS defibrillators. There were no significant differences in time from arrest to first shock (8.0 vs 8.1 minutes), nor were ther e any differences in the size of the communities involved. The shocks resulted in the following rhythms: organized rhythm: TE: 15 of 130 (12 %), DS: 24 of 108 (22%), p=0.10 (NS); persistent VF: TE: 85 of 130 (65 %), DS: 45 of 108 (42%), p <0.01; asystole: TE: 30 of 130 (23%), DS: 3 9 of 108 (36%), p=NS; and survival to hospital discharge: TE: 5 of 44 (11%), DS: 8 of 42 (19%), p=NS. We conclude that DS waveforms terminat ed VF more frequently than TE, but there was no significant difference in resumption of an organized rhythm or survival. A prospective compa rison of these 2 waveforms is needed. (C) 1996 by Excerpta Medica, Inc .