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.