Sudden cardiac death (SCD) from any cause claims 300,000–400,000 lives a year in the US. Implantable cardioverter/defibrillators (ICDs) can detect ventricular fibrillation (VF) and terminate it. For determining the optimal defibrillation threshold, ventricular fibrillation is repetitively induced intraoperatively and terminated using DC shocks of different energy. Depending on the protocol employed, several fibrillation/defibrillation sequences are mandatory before the final implantation of an ICD, thus providing an elegant model to study how LV peak pressure and RR interval develop after the termination of VF in anaesthetized patients. The 34 patients (6 females; 18%) averaged 59±10 years (from 33 to 79 years). The anaesthetic regimen was standardized for all patients. Anaesthesia was maintained with 1.5% enflurane. The ventilation was controlled; the end-expiratory pressure was set to zero. Left ventricular (LV) pressure was assessed using a microtip-catheter. ECG leads I, III und V₅ were recorded. In all patients, VF was induced with a fibrillator. After conclusion of the defibrillation threshold testing and implantation of the cardioverter/defibrillator, the functionality of the implanted device was tested by a final induction of VF and its subsequent termination by the ICD (the device test). LV peak pressure after a total of 157 VF terminations was used to derive an exponential function: LVP (t) = A x (-exp(-t/τLVP)) + B, with A, factor to determine the starting pressure [mmHg] at t = 0 s; τLVP, constant of LV pressure increase [beats]; and B, non-zero asymptote [mmHg]. The decrease in the RR-interval (RRI) was described with the exponential equation: RRI (t) = C x exp(-t/τRRI) + D, with C, factor to determine the starting RRI [s] at t = 0 s; τRRI, constant of RRI increase [beats]; and D, non-zero asymptote [s]. Data are means±SD. The exponential equation described the time-dependent peak LVPs and the RRIs very closely (r2 was 0.96±0.08 and 0.62±0.27 respectively). The LVP increased with a constant of 8±3 beats. The RRI decreased clearly quicker with a constant of 2±1 beats (t test, P<0.05). After termination of VF, peak LVP will plateau after about 40 beats whereas the heart rate will already plateau after about 10 beats, i.e. after 5 times τ. Thus, the heart ’finds’ a steady state rhythm quicker than the individual peak systolic pressure does.