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 c ontrol amplifiers the maximum possible sensitivity is programmed with the a im of securing optimal detection of ventricular fibrillation. This study wa s designed to prove that a reduction in maximum sensitivity is safe with re spect to appropriate sensing of ventricular fibrillation, while avoiding se nsing of extracardiac signals. Methods and Results Forty-two consecutive patients, undergoing defibrillato r implantation/replacement with programmable maximum auto-gain sensing sens itivity (Ventak Mini III(TM). Ventak AV(TM), 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(TM) , Guidant, St. Paul, MN, U.S.A.), eight patients received a single-coil lea d system with true bipolar sensing (Sprint(TM), Medtronic, Minneapolis, MN, U.S.A.). During device implantation and pre-discharge testing, arrhythmia detection times of induced ventricular fibrillation were compared at progra mmed maximum (0.18 mV) and minimum (0.43 mV) sensitivity in a randomized ma nner. Seventy-six induced episodes of ventricular fibrillation were analyse d. The mean arrhythmia detection times did not differ between the programme d sensing levels (maximum sensitivity: 1612+/-307 ms. vs minimal sensitivit y: 1602+/-330 ms; P=ns). The results were not affected by the type of impla nted lead system (integrated bipolar versus true bipolar sensing). Conclusion In the implantable defibrillator devices, reduction in maximum s ensitivity did not impair the detection of induced episodes of ventricular fibrillation. (Europace 2000; 2: 160-162) (C) 2000 The European Society of Cardiology.