title: Biphasic defibrillation using a single capacitor with large capacitance: reduction of peak voltages and ICD device size.
abstract: The volume of current implantable cardioverter defibrillators (ICD) is not convenient for pectoral implantation. One way to reduce the size of the pulse generator is to find a more effective defibrillation pulse waveform generated from smaller volume capacitors. In a prospective randomized crossover study we compared the step-down defibrillation threshold (DFT) of a standard biphasic waveform (STD), delivered by two 250-microF capacitors connected in series with an 80% tilt, to an experimental biphasic waveform delivered by a single 450-microF capacitor with a 60% tilt. The experimental waveform delivered the same energy with a lower peak voltage and a longer duration (LVLD). Intraoperatively, in 25 patients receiving endocardial (n = 12) or endocardial-subcutaneous array (n = 13) defibrillation leads, the DFT was determined for both waveforms. Energy requirements did not differ at DFT for the STD and LVLD waveforms with the low impedance (32 +/- 4 omega) endocardial-subcutaneous array defibrillation lead system (6.4 +/- 4.4 J and 5.9 +/- 4.2 J, respectively) or increased slightly (P = 0.06) with the higher impedance (42 +/- 4 omega) endocardial lead system (10.4 +/- 4.6 J and 12.7 +/- 5.7 J, respectively). However, the voltage needed at DFT was one-third lower with the LVLD waveform than with the STD waveform for both lead systems (256 +/- 85 V vs 154 +/- 51 V and 348 +/- 76 V vs 232 +/- 54 V, respectively). Thus, a single capacitor with a large capacitance can generate a defibrillation pulse with a substantial lower peak voltage requirement without significantly increasing the energy requirements. The volume reduction in using a single capacitor can decrease ICD device size.
authors.affiliation: Department of Cardiology/Angiology, Hospital of the Westfälische Wilhelms-University of Münster, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Block
authors.forename: D
authors.initials: D
authors.lastname: Hammel
authors.forename: D
authors.initials: D
authors.lastname: Böcker
authors.forename: M
authors.initials: M
authors.lastname: Borggrefe
authors.forename: T
authors.initials: T
authors.lastname: Budde
authors.forename: F
authors.initials: F
authors.lastname: Isbruch
authors.forename: H H
authors.initials: HH
authors.lastname: Scheld
authors.forename: G
authors.initials: G
authors.lastname: Breithardt
mesh_terms: D000328:Adult; D000368:Aged; D018592:Cross-Over Studies; D017147:Defibrillators, Implantable; D004562:Electrocardiography / Q000295:instrumentation*; D004867:Equipment Design; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012815:Signal Processing, Computer-Assisted / Q000295:instrumentation*; D017180:Tachycardia, Ventricular / Q000503:physiopathology / Q000628:therapy*; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000503:physiopathology / Q000628:therapy*