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 (P_LV), and the incidence and type of arrhythmias after effective low-dose defibrillation (I_max = 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 $\text{1}\text{2}$ to 3 hours after occlusion of a part of the left anterior descending artery by a catheter technique. Time to recovery of P_LV depended on duration of fibrillation (t_F) and cumulative defibrillation current ($\text{I}\text{1}\text{2}$), and became critical at t_F > 45 seconds and $\text{I}\text{1}\text{2}\text{> 45 A}$. Total duration of arrhythmias due to defibrillation increased with increasing t_F and $\text{I}\text{1}\text{2}$. Arrhythmias which have a relative greater chance of resulting in refibrillation or which may seriously decrease the cardiac output occurred more often with $\text{I}\text{1}\text{2}\text{> 55 A}$ (p < 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.