Efficacy of lower-energy biphasic shocks for transthoracic defibrillation: a follow-up clinical study.
OBJECTIVE
This clinical study prospectively evaluated the first-shock defibrillation efficacy of 150-joule impedance-compensated, 200-microF biphasic truncated exponential (BTE) shocks in patients with electrically-induced ventricular fibrillation (VF), and compared it with a historical control group treated with 200-J monophasic damped sine (MDS) shocks.


METHODS
Ventricular tachyarrhythmias were induced in patients undergoing electrophysiologic (EP) testing for ventricular arrhythmias or testing of an implantable cardioverter-defibrillator (ICD). A 150-J shock was delivered as the primary therapy to terminate induced arrhythmias in the EP group, and as a "rescue" shock when a single ICD shock failed to terminate the arrhythmias in the ICD group.


RESULTS
Ninety-six patients received study shocks. The preshock rhythm was classified as VF in 77 patients and as ventricular tachycardia (VT) in 19 patients. First-shock success rates for VF and VT were 75 out of 77 (97.4%) and 19 out of 19 (100%) for the 150-J BTE compared with the historical control rates of 61 out of 68 (89.7%) and 29 out of 31 (94%) for 200-J MDS. The first-shock success rate for VF treated with 150-J BTE was technically equivalent to that of 200-J MDS (p=0.001). The transthoracic impedance did not vary between groups, yet the peak current delivered by the 150-J BTE shock was about 50% lower.


CONCLUSIONS
This study demonstrated that 150-J shocks of this impedance-compensated, 200-microF BTE waveform provided very high efficacy for defibrillation of short duration, electrically-induced VF. These lower-energy biphasic shocks had a success rate equivalent to that of 200-J MDS shocks, and they provided this efficacy while exposing patients to much less current than the monophasic shocks.
Scripps Memorial Hospital, La Jolla, California 92037, USA. epdoc@cardiacarrhythmia.org
Steven L
SL
Higgins
Sharon G
SG
O'Grady
Isabelle
I
Banville
Fred W
FW
Chapman
Paul W
PW
Schmitt
Paula
P
Lank
Robert G
RG
Walker
Marina
M
Ilina
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002307:Cardiography, Impedance; D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012494:Sampling Studies; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*