Defibrillation shocks at 1.5xE-DFT had significantly higher efficacy for electrically induced ischemic VF (76%) compared to spontaneous VF (31%), which often recurred before ECG recovery.
Does defibrillation efficacy differ between spontaneous and electrically induced ventricular fibrillation during acute ischemia or reperfusion in a porcine model?
Spontaneous ventricular fibrillation can be halted by a shock but quickly restart before ECG amplifier recovery, falsely appearing as a failed shock, which explains the higher apparent defibrillation threshold for spontaneous VF.
Absolute Event Rate: 76% vs 31%
BACKGROUND: Shocks that have defibrillated spontaneous ventricular fibrillation (VF) during acute ischemia or reperfusion may seem to have failed if VF recurs before the ECG amplifier recovers after shock. This could explain why the defibrillation threshold (DFT) for spontaneous VF appears markedly higher than for electrically induced VF. METHODS AND RESULTS: The DFT for electrically induced VF (E-DFT) was determined in 15 pigs before ischemia, followed by left anterior ascending or left circumflex artery occlusion. VF was electrically induced 20 minutes after occlusion, followed 5 minutes later by reperfusion. Whether spontaneous or electrically induced, VF during occlusion or reperfusion was treated with up to 3 shocks at 1.5xE-DFT. If all 3 shocks failed, shock strength was increased. Thirty minutes after reperfusion, the other artery was occluded and the protocol was repeated. Defibrillation was considered successful if postshock sinus/idioventricular rhythm was present for > or = 30 seconds. VF recurring within 30 seconds after the shock was considered immediate or delayed if the first postshock activation complex in a rapidly restored ECG recording was VF or sinus/idioventricular rhythm, respectively. Defibrillation efficacy at 1.5xE-DFT was significantly higher for electrically induced ischemic VF (76%) than for spontaneous VF (31%). The incidence of delayed recurrence after electrically induced nonischemic (3%) or ischemic (20%) VF was significantly lower than after spontaneous VF (75%). Mean VF recurrence time after spontaneous VF was 4.6+/-5.3 seconds. CONCLUSIONS: Spontaneous VF can be halted by a shock but then quickly restart before a standard ECG amplifier has recovered from postshock saturation, making it appear that the shock failed.
Qin et al. (Tue,) conducted a other in Ventricular fibrillation during acute ischemia or reperfusion (n=15). Defibrillation shocks vs. Spontaneous ventricular fibrillation was evaluated on Defibrillation efficacy at 1.5xE-DFT. Defibrillation shocks at 1.5xE-DFT had significantly higher efficacy for electrically induced ischemic VF (76%) compared to spontaneous VF (31%), which often recurred before ECG recovery.