Improved implantable cardioverter-defibrillator shock efficacy using programmable pulse width

Each phase of a biphasic implantable cardioverter-defibrillator (ICD) shock waveform can be characterized by either the percentage of peak voltage that decays (tilt) or the time taken for that decay (pulse width). Although shock programming has typically relied on fixing the tilt, patient-specific fixed pulse widths may improve shock success.

The purpose of this study was to compare shock energies and success rates to treat spontaneous ventricular tachycardia/ventricular fibrillation using ICD/CRT-D (cardiac resynchronization therapy - defibrillator) devices with fixed pulse width vs fixed tilt waveforms.

US patients with single-coil ICD or CRT-D devices (Ellipse, Assura, Unify, and Fortify, Abbott) were identified who had received defibrillation or cardioversion shock therapy (≥1 episode) when programmed to both 65% fixed tilt and fixed pulse width modes for distinct periods. Patient demographic characteristics, programming, and shock episodes were downloaded from the Merlin.net Patient Care Network (Abbott). Shock energies and success rates were compared across shock waveform types within each patient.

In total, 277 patients experiencing at least 1 shock-delivered episode with each shock type were evaluated (mean age 70 ± 14 years; 157 [57%] with ICDs; 120 [43%] with CRT-Ds). The first-shock success rate was significantly greater with fixed pulse width vs fixed tilt (median [25th, 75th percentile] 100.0% [75.0%, 100.0%] of episodes vs 87.5% [42.1%, 100.0%] of episodes; P < .001), and more patients experienced 100% first-shock success with fixed pulse width vs fixed tilt (69.3% of episodes vs 46.2% of patients; P < .001). With fixed pulse width, 79.4% of patients (220 of 277) experienced greater-or-equal first-shock success, and they did so by delivering comparable energies (33.0 [29.6, 35.1] J vs 32.9 [25.7, 36.9] J; P = .53).

Reprogramming shock waveforms from 65% fixed tilt to fixed pulse width significantly improved intrapatient shock success.