Is High-Voltage Lead Integrity Measurement Adequate During Defibrillator Generator Replacement ?

The necessity for defibrillator testing at the time of implant or generator replacement is widely debated. The need for administering a shock at time of implant is lessened by the use of high-voltage integrity checks commonly employed by all device manufacturers. We report a case of a patient with a lead under safety advisory (St. Jude Riata 1580) and known externalization of conductors with no prior electrical abnormalities who underwent routine generator replacement. After the generator replacement, the high-voltage integrity check was normal, but during defibrillator testing the device was unable to deliver high-voltage therapy after successful induction of ventricular fibrillation. This was repeated after reinterrogation of the device, again showing normal high-voltage integrity and once again it failed to deliver life-saving therapy. Both failures were a result of a low impedance, and subsequent interrogation revealed nondetectable impedance consistent with a short in the high-voltage circuit. Lead analysis revealed a short in the high-voltage circuit not related to externalization of conductor wires. This case illustrates the importance of delivering an actual high-voltage shock to determine the circuit integrity for a defibrillator system at time of implant or replacement.