Aims: Dual coil (DC) electrodes are preferred to single coil (SC) electrodes because of an assumed higher shock efficacy. However, DC-electrodes may be associated with an increased difficulty and risk of lead extraction. We aimed to compare SC- and DC-electrodes with respect to the first shock efficacy (FSE) after implantable cardioverter defibrillator (ICD) implantation.

Methods and results: One thousand and seventy-seven patients of the NORDIC ICD trial were randomly assigned to first time ICD implantation with or without defibrillation (DF) testing. The electrode configuration was determined before randomization. One thousand and sixty-seven patients eventually received an ICD, 516 (48.4%) with a SC- and 551 (51.6%) with a DC-electrode. DC-electrodes were preferentially selected in older patients, renal failure, atrial fibrillation, dual chamber, Cardiac Resynchronization Therapy (CRT) devices, angiotensin-converting-enzyme (ACE) inhibitors/angiotensin (AT) receptor blockers and without Sotalol. However, the preference of the investigational site was dominant over clinical parameters. The DF energy at the final electrode position was higher in SC-electrodes (adjusted difference +1.15 J; P = 0.005; only patients tested). Less patients with DC-electrodes required intra-operative system reconfiguration (adjusted difference -3.9; P = 0.046; only patients tested). Using mixed logistic regression, the FSE was 92.6% in SC- and 97.8% in DC-electrodes (adjusted odds ratio 4.3 (95% confidence interval [1.9, 9.8]; P < 0.001)).

Conclusion: Dual coil-electrode selection mainly depends on the preference of the investigational site and seems to be preferred in older patients, renal failure, atrial fibrillation, dual chamber, and CRT devices. Patients with DC-electrodes required less intraoperative system reconfigurations. Dual coil-electrodes provided a substantially higher FSE during follow-up. Mortality rates were not significantly different in patients with DC- and SC-electrodes.