Estimation of Acute Myocardial Infarct Size

This study was performed to determine the relationship between myocardial infarct size estimated by serum CK-MB methods and the extent of irreversible injury in acute myocardial infarction. In 321 consecutive patients, infarct size was estimated by different mathematical models, and in 22 patients who died in hospital, the extent of myocardial necrosis was determined by autopsy. We also investigated the depletion of CK-MB in infarcted tissue, the recovery of CK-MB in the plasma volume, and the elimination ofCK-MB from plasma. Myocardial CK-MB depletion was relatively greater in the larger infarcts, whereas the recovery of enzyme in plasma was independent of the infarct size. Correction of serum CK-MB for changes in plasma volume improved the estimate significantly (p < 0.05). The correlation between the measured infarct size (g) and the estimated infarct size (units per liter and gram-equivalents) was highly significant (r = 0.85-0.89, SEE = 23-27%, p < 0.001). Thus, a semiquantitative expression of the extent of myocardial necrosis can be determined in vivo.