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Prediction of Infarct Size with Baboons: A Proposed Model for Accurately Determining the Efficacy of Therapeutic Interventions

A primate model is described which allows quantitative prediction of myocardial necrosis (measured histologically at 1 week) from the area of ST segment elevation (ST$) recorded by a high resolution matrix of fixed epicardial electrodes. The predictive validity of the model is based on the production of infarcts which are transmural, limited to the left ventricular free wall, and in which the infarct volume bears a relatively uniform relationship to its epicardial surface. The electrode grid circumscribes the area of necrosis in the anterior free wall of the left ventricle (LV) produced by occlusion of a diagonal branch of the left anterior descending coronary artery (LAD). The pattern of changes in ST$ was examined throughout its evolution, and changes in the distribution of ST$ were documented. Central points within the area of ST$ consistently showed greater absolute values of ST$, and ST segments remained elevated longer than those recorded through more peripheral electrodes. Electrodes at the base demonstrated a greater magnitude of ST$ than electrodes near the apex. The number of electrodes (NST), i.e., the area of electrode matrix corresponding to those electrode points with significant ST$ (area of ST$) at each recording interval through 8 hours, was fit to the area of necrosis underlying the grid. Maximum area of ST$ (maxAST) uniformly overestimated the infarct size between animals by about 25%; however, regression analysis allowed prediction of the extent of infarction from maxAST with an error of only 5%. Correlation of maxAST with epicardial extent of infarction and total weight and volume of infarction yielded coefficients of 0.95, 0.83, and 0.91, respectively. Maximum mean ST$ (ST$) showed a poorer correlation with the epicardial extent, weight, and volume: coefficients were 0.49, 0.55, anj 0.39, respectively. Thus, maxAST correlated closely with extent of necrosis and proved an accurate predictor of infarct size.