Benefit of millisecond waveform durations for patients with high defibrillation thresholds.
BACKGROUND
Patients with a high defibrillation threshold (DFT) present an atypical but vexing problem with regard to implantable cardioverter-defibrillator (ICD) therapy. Their implant procedures are lengthy and involve more risk of complications. These patients often sustain a reduced safety margin that may compromise their survival.


OBJECTIVE
The purpose of this study was to evaluate the use of fixed millisecond duration model-optimized biphasic waveforms compared with conventional tilt-based waveforms in patients having a high DFT.


METHODS
We compared a 65%/65% tilt biphasic waveform to a millisecond duration biphasic waveform based on the biphasic burping theory using a 90-microF shock capacitor.


RESULTS
Fifty-four patients were evaluated. Mean DFT with tilt was reduced from 11.0 +/- 5.5 J to 8.8 +/- 4.1 J, for a mean reduction of 20% (P < .0001). For the 13 patients with tilt-based DFTs > or = 15 J, DFT was reduced from 18.7 +/- 4.1 J to 13.4 +/- 3.5 J, for a mean DFT reduction of 28% (P = .009). The population peak DFT was reduced from 29.0 J to 17.5 J, for a 41% reduction (P = .03).


CONCLUSIONS
Use of simple millisecond biphasic waveforms instead of conventional tilt-based waveforms can lead to substantial reductions in DFT, especially in patients with high DFT.
Denman
Russell A
RA
Department of Cardiology, The Prince Charles Hospital, Brisbane, Australia.
Umesan
Chirammal
C
Martin
Paul T
PT
Forbes
Ross N
RN
Kroll
Mark W
MW
Anskey
Emma J
EJ
Burnett
Helen E
HE
D000328:Adult; D000368:Aged; D017147:Defibrillators, Implantable / Q000009:adverse effects; D004554:Electric Countershock / Q000009:adverse effects / Q000379:methods*; D017097:Electric Impedance; D004867:Equipment Design; D005260:Female; D019220:High-Energy Shock Waves; D006801:Humans; D008297:Male; D008875:Middle Aged; D012107:Research Design; D018570:Risk Assessment; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000628:therapy