Synchronized defibrillation shock delivery based on endocardial ventricular fibrillation waveform analysis is lead dependent

Previous studies have demonstrated that the defibrillation efficacy can be improved if the shock is synchronized at a high absolute VF voltage (AVFV) peak recorded from lead II of the ECG. In this study, two different endocardial lead configurations, SY1:RV-coil (+) ↔ (SVC-coil+Can) (-) and SY2:RV-coil(+) ↔Can(-), were tested utilizing the peak shock method in a close-chest canine model (SY1:n=2, SY2:n=7). The leads were used both for sensing the VF signal and for the shock delivery. The performance of this new peak shock method was compared to the conventional method of shocking at fixed time in 225 paired trials. For SY1, the peak shock method did not improve the success comparing with the conventional shock method. For SY2, peak shock method performed better in four (4) of the seven (7) subjects (8%-40% increase) and no difference in one. In the remaining two cases, additional 4-5 shock trial pairs were tested using lead II of the ECG for sensing and the performance with the peak shock was improved. The synchronized shock based on VF waveform analysis using endocardial electrograms recorded from the same electrodes for shocking may be potentially useful for implantable devices if further studies can identify an optimal endocardial lead.