Benefit of millisecond waveform durations for patients with high defibrillation thresholds

BackgroundPatients 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.ObjectivesThe 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.MethodsWe compared a 65%/65% tilt biphasic waveform to a millisecond duration biphasic waveform based on the biphasic burping theory using a 90-μF shock capacitor.ResultsFifty-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 ≥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).ConclusionUse of simple millisecond biphasic waveforms instead of conventional tilt-based waveforms can lead to substantial reductions in DFT, especially in patients with high DFT.