Implantable intravascular defibrillator: Defibrillation thresholds of an intravascular cardioverter-defibrillator compared with those of a conventional ICD in humans

Background A percutaneous intravascular cardioverter-defibrillator (PICD) has been developed with a right ventricular (RV) single-coil lead and titanium electrodes in the superior vena cava (SVC)–brachiocephalic vein (BCV) region and the inferior vena cava (IVC). Objective To compare defibrillation thresholds (DFTs) of the PICD with those of a conventional ICD in humans. Methods Ten patients with ischemic cardiomyopathy and ejection fraction ≤35% were randomized to initial testing with either PICD or conventional ICD. A standard dual-coil lead was positioned in the RV apex. If randomized to PICD, the device was placed into the vasculature such that 1 titanium electrode was positioned in the SVC-BCV region and the second in the IVC. For PICD DFTs, the RV coil of the conventional ICD lead was connected to the PICD mandrel [shock vector: RV (+) to SVC-BCV (−) + IVC (−)]. When testing the conventional ICD, a subcutaneous pocket was formed in the left pectoralis region and the ICD was connected to the lead system and positioned in the pocket [shock vector: RV (+) to SVC (−) + active can (−)]. Each device was removed before testing with the other. A step-down binary search protocol determined the DFT, with the initial shock being 9 J. Results The mean PICD DFT was 7.6 ± 3.3 J, and the conventional ICD system demonstrated a mean DFT of 9.5 ± 4.7 J (N = 10; paired t test, P = .28). Conclusion The intravascular defibrillator has DFTs similar to those of commercially available ICDs.