Detection of ventricular fibrillation in implantable defibrillators with automatic gain control amplifiers: effects of programming sensitivity.

AIMS

In newer implantable cardioverter-defibrillators with automatic gain control amplifiers the maximum possible sensitivity is programmed with the aim of securing optimal detection of ventricular fibrillation. This study was designed to prove that a reduction in maximum sensitivity is safe with respect to appropriate sensing of ventricular fibrillation, while avoiding sensing of extracardiac signals.

METHODS AND RESULTS

Forty-two consecutive patients, undergoing defibrillator implantation/replacement with programmable maximum auto-gain sensing sensitivity (Ventak Mini III, Ventak AV , Guidant, St. Paul, MN, U.S.A.), were prospectively investigated. Thirty-four patients were implanted with a dual-coil lead system, providing integrated bipolar sensing (Endotak, Guidant, St. Paul, MN, U.S.A.), eight patients received a single-coil lead system with true bipolar sensing (Sprint, Medtronic, Minneapolis, MN, U.S.A.). During device implantation and pre-discharge testing, arrhythmia detection times of induced ventricular fibrillation were compared at programmed maximum (0.18 mV) and minimum (0.43 mV) sensitivity in a randomized manner. Seventy-six induced episodes of ventricular fibrillation were analysed. The mean arrhythmia detection times did not differ between the programmed sensing levels (maximum sensitivity: 1612 +/- 307 ms, vs minimal sensitivity: 1,602 +/- 330 ms; P = ns). The results were not affected by the type of implanted lead system (integrated bipolar versus true bipolar sensing).

CONCLUSION

In the implantable defibrillator devices, reduction in maximum sensitivity did not impair the detection of induced episodes of ventricular fibrillation.