Use of changes in the epicardial QRS complex to assess interventions which modify the extent of myocardial necrosis following coronary artery occlusion.

The goal of this study was to determine if changes in the epicardial QRS complex after coronary artery occlusion (CAO) can be used to evaluate the efficacy of interventions designed to limit infarct size. Forty-one open-chest dogs with CAO were studied: 15 were controls, 18 received hyaluronidase and eight received propranolol starting 20 minutes after CAO. Epicardial ECGs were recorded at specific time intervals to analyze ST-segment elevation and changes in Q and R waves. Transmural specimens were obtained 24 hours after CAO from the same sites at which ECGs were recorded. Q wave development (deltaQ), R wave fall (deltaR), and their combination (deltaR + deltaQ) at 24 hours correlated with the extent of necrosis, as determined by myocardial creatine phosphokinase activity depression and histologic appearance. In the control group ST-segment elevation 15 minutes after CAO (ST15M) predicted changes in Q and R waves 24 hours later; in the treated groups, the same ST15M prior to drug administration resulted in significantly less QRS changes. Thus, 1) Q wave development and R wave fall 24 hours after CAO accurately reflect myocardial necrosis. 2) ST15M predicts subsequent changes in Q and R waves. 3) The efficacy of hyaluronidase and propranolol, agents previously shown to reduce myocardial necrosis, can be detected by less Q wave development and a smaller fall in R wave voltage.