Regional distribution of the MB isoenzyme of creatine kinase in the human heart.

Human myocardial tissue obtained at autopsy from ten patients was examined for content of the MB isoenzyme of creatine kinase (CK-MB). We wished to determine whether this isoenzyme is distributed homogeneously throughout the heart. In eight cases, there was no history or pathological evidence of heart disease. Two had a history of previous myocardial infarction; in these, tissue was obtained from sites distant from the scar. Difference was found between the CK-MB content of the right atrium and the left atrium, and between the right ventricle and left ventricle. In all cases, the CK-MB content of the right side of the heart significantly exceeded that of the left side of the heart. Statistically significant differences were also found between the CK-MB content of the anterior interventricular septum and that of the posterior septum. These topographical variations in CK-MB content may be related to differences in the density of contractile elements in various parts of the heart and, moreover, are not taken into account in the enzymatic estimation of infarct size.