[Progressive decrease of the causes that maintain ventricular fibrillation after experimental coronary occlusion].
Progressive diminution of the causes that maintain ventricular fibrillation after coronary occlusion. Extracorporeal circulation was performed on a group of normal dogs in which a ligature was placed on the left anterior descending coronary artery, immediately beneath the bifurcation of the left coronary artery. The incidence of ventricular fibrillation was of 15 dogs out of 20 (table 1). In a control group without extracorporeal circulation ventricular fibrillation appeared in 24 dogs out of 30 (table 2). These results demonstrate that extracorporeal circulation performed with the idea of improving coronary circulation does not prevent ventricular fibrillation in coronary occlusion. In those dogs with the cross circulation, attempts to defibrillate the ventricles with an electric a.c. defibrillator (three electrical shocks applied directly on the myocardium every 4 or 5 minutes) were uniformly unsuccessful until a period ranging from 12 to 80 minutes elapsed after the onset of ventricular fibrillation. After these periods all fibrillating dogs were defibrillated and recovered either normal or idioventricular rhythm. It is assumed that a "fibrillator substance" liberated by the injury in the initial state of infarction is washed out of the myocardium, or a zone of increased excitability and conduction disturbance is progressively eliminated so that the chances of originating circus movements are diminished.