Derangements of myocardial metabolism preceding onset of ventricular fibrillation after coronary occlusion

Abstract

To determine alterations in myocardial metabolism and and hemodynamics that occur within the first 30 minutes after coronary arterial occlusion, before the onset of ventricular fibrillation, measurements were compared in two series of dogs. Series A, 90 dogs that did not manifest ventricular fibrillation after coronary occlusion, were considered a control group. Series B consisted of 28 dogs that had ventricular fibrillation within 30 minutes after occlusion. All had similar comprehensive measurements completed preceding the onset of ventricular fibrillation. The animals in series B (subseuqnt fibrillation) had significantly higher heart rates before and after coronary occlusion. In this series cardiac metabolism of the occluded segment judged by transmyocardial lactate extraction, potassium balance, sodium/potassium ratio and blood pH because grossly more abnormal after coronary occlusion than in series A. In 5 animals whose measurements were obtained within 5 minutes of the onset of ventricular fibrillation, a sudden massive lactate production, potassium loss and increased acidosis of the occluded portion supervened minutes before the onset of the fatal arrhythmia. Animals with ventricular fibrillation had higher intracoronary S-T segment elevation that persisted until the onset of ventricular fibrillation. Measurements of abnormal hemodynamic function (left ventricular end-diastolic pressure, peak systolic pressure and first derivative of left ventricular pressure [DP/dt]) were not associated with an increased incidence of ventricular fibrillation. The study indicates that animals that manifest ventricular fibrillation within 30 minutes after coronary occlusion have higher preocclusion heart rates, a more severe metabolic disorder of the coronary occluded segment and more persistent intracoronary S-T segment elevation compared with animals that do not manifest ventricular fibrillation.