Abstract
An Objective of this study is to describe the characteristics of ventricular fibrillation (Vf) for successful defibrillation. Ten piglets were subjected to this study. Animals were ventilated with room air under anesthesia and Vf was induced with 50 volt AC for 3 seconds. Cardiopulmonary resuscitation was started 8 minutes after the induction. Closed-chest compression was standardized by using a mechanical chest compressor. Either epinephrine or propranolol, lidocaine and bretylium were given intravenously and DC shocks (100 joules) were delivered every one minute for 5 minutes until cardiac rhythm was restored. The lead II ECG in the course of resuscitation were recorded every one minute after induction of Vf. The Vf patterns were also recorded as digital signals for 4 seconds and used for fast fourier transform analysis on line. Both amplitude and frequency at peak level were successively presented on the spectrum analysis. As a result we succeeded in defibrillation in 5 piglets (=Success group) out of ten. Electrophysiological study revealed that the peak amplitude suddenly decreased at 3 minutes after the induction of Vf and thereafter (P<0.01 vs baseline), that the peak frequency remained more than 10Hz for 5 minutes and gradually decreased following time course (P<0.01 vs baseline), that the increase of amplitude resulted from CPR (P<0.01 vs at beginning of CPR), and that the increase of frequency was observed just before the successful DC (P<0.01 vs at 8 beginning of CPR) in Success group. The amplitude-frequency distribution of successful defibrillation on a scatter diagram was clearly defined from that of failed DC's (P<0.01). We conclude that spectral analysis of Vf waveforms offers us better information for successful defibrillation than raw Vf waveforms and that successful defibrillation seems to depend on recovery in both frequency and amplitude.
