title: Prospective comparison of biphasic and monophasic shocks for implantable cardioverter-defibrillators using endocardial leads.
abstract: Bidirectional shocks using 2 current pathways have been used in endocardial lead systems for implantable cardioverter-defibrillators, but the optimal shock waveform for endocardial defibrillation is unknown. The clinical efficacy and electrical characteristics of bidirectional monophasic and biphasic shocks for endocardial cardioversion-defibrillation of fast monomorphic or polymorphic ventricular tachycardia (VT), or ventricular fibrillation (VF) were evaluated. Thirty-three patients (mean age 60 +/- 12 years, and mean left ventricular ejection fraction 34 +/- 13%) were studied. Defibrillation catheter electrodes were located in the right ventricular apex and superior vena cava/right atrial junction. A triple-electrode configuration including the 2 catheter electrodes and a left thoracic patch was used to deliver bidirectional shocks from the right ventricular cathode to an atrial anode (pathway 1) and the thoracic patch (pathway 2). The shock waveforms examined were sequential and simultaneous monophasic, and simultaneous biphasic. The efficacy of 580 V (20 J) shocks for fast monomorphic VT were comparable for the 3 waveforms (73% for sequential monophasic, 73% for simultaneous monophasic, and 100% for simultaneous biphasic). However, for polymorphic VT and VF, 580 V sequential monophasic shocks had a significantly lower efficacy (25%) than did simultaneous monophasic (75%; p = 0.01) or biphasic (89%; p less than 0.001) shocks. Single-shock defibrillation thresholds with simultaneous biphasic shocks were significantly lower (9 +/- 5 J) than were those with simultaneous monophasic shocks (15 +/- 4 J; p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Cardiology, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, Newark.
authors.forename: S
authors.initials: S
authors.lastname: Saksena
authors.forename: H
authors.initials: H
authors.lastname: An
authors.forename: R
authors.initials: R
authors.lastname: Mehra
authors.forename: P
authors.initials: P
authors.lastname: DeGroot
authors.forename: R B
authors.initials: RB
authors.lastname: Krol
authors.forename: E
authors.initials: E
authors.lastname: Burkhardt
authors.forename: D
authors.initials: D
authors.lastname: Mehta
authors.forename: T
authors.initials: T
authors.lastname: John
mesh_terms: D004554:Electric Countershock / Q000295:instrumentation / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019736:Prostheses and Implants; D013610:Tachycardia / Q000628:therapy; D014693:Ventricular Fibrillation / Q000628:therapy