Arrhythmias and left ventricular function after defibrillation during acute myocardial infarction in the intact dog.

The purpose of this study was to assess the recovery of the left ventricular pressure (PLV), and the incidence and type of arrhythmias after effective low-dose defibrillation (Imax = 18-70 A) in healthy hearts and in hearts with acute myocardial infarction (AMI) in the intact dog. In fifteen dogs 84 episodes of fibrillation-defibrillation were studied in the healthy heart and 53 episodes were studied in the acute phase of myocardial infarction 1/2 to 3 hours after occlusion of a part of the left anterior descending artery by a catheter technique. Time to recovery of PLV depended on duration of fibrillation (tF) and cumulative defibrillation current (I 1/2), and became critical at tF greater than 45 seconds and I 1/2 greater than 45 A. Total duration of arrhythmias due to defibrillation increased with increasing tF and I 1/2. Arrhythmias which have a relative greater chance of resulting in refibrillation or which may seriously decrease the cardiac output occurred more often with I 1/2 greater than 55 A (p less than 0.001), when 50% of episodes were followed by these arrhythmias. No differences were found in responses between the healthy heart and the heart with AMI.