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Document Details :

Title: Thransthoracic defibrillation of short lasting ventricular fibrillation
Subtitle: A randomised trial for comparison of the efficacy of low-energy biphasic rectilinear and monophasic damped sine shocks
Author(s): SZILI-TOROK, Tamas , THEUNS, Dominic , VERBLAAUW, Ton , SCHOLTEN, Marcoen , KIMMAN, Geert-Jan , RES, Jan , JORDAENS, Luc
Journal: Acta Cardiologica
Volume: 57    Issue: 5   Date: October 2002   
Pages: 329-334
DOI: 10.2143/AC.57.5.2005448

Abstract :
Background— Biphasic rectilinear shocks are more effective than monophasic shocks for transtho-
racic atrial defibrillation and for ventricular arrhythmias during electrophysiological testing.We under-
took the present study to compare the efficacy of 100 J rectilinear biphasic waveform shocks with
150 J monophasic damped sine waveform shocks for transthoracic defibrillation of true ventricular
fibrillation during defibrillation threshold testing (DFT).The second aim of the study was to analyse
the influence of patch positions on the efficacy of defibrillation.
Methods— 50 episodes of 14 patients (age ranging from 37 to 82 years) who underwent DFT testing were randomised for back-up shocks with either a sequence of 100 and 200 J biphasic waveform, or a sequence of 150 and 360 J conventional monophasic shocks.A binary search protocol was used at implantation and before hospital discharge.Patients were also randomised to an antero-posterior position versus a right-anterior-apical position. A crossover was performed between implantation and pre-hospital discharge for biphasic versus monophasic sequence as well as for the 2 different positions.

Results— After failed internal shocks, 27 episodes were treated with biphasic, and 23 with monophasic shocks. The first attempt by the external device did not terminate 11 episodes (2 biphasic, 9 monophasic). The first shock efficacy was significantly greater with biphasic than with monophasic shocks (p<0.02). The overall success rate was 93% with biphasic shocks and 64% with monophasic shocks. In multivariate regression analysis including patch position, arrhythmia duration, type of wave- form, testing order and session,only waveform was associated with successful defibrillation (p<0.02).

Conclusion— For transthoracic defibrillation of ventricular fibrillation, low-energy rectilinear biphasic shocks are more effective than monophasic shocks. The position of the defibrillation shock pads has no influence on the biphasic shock efficacy, but anteroposterior pad position is more effective using monophasic shocks.