Early, reliable detection of acute myocardial infarction and of coronary artery recanalization, in patients receiving thrombolytic agents, is essential to guide the course of therapy. Because the MM and MB isoenzymes of creatine kinase (CK) released from myocardium, undergo time-dependent removal of carboxyl terminal lysine residues from each monomer during exposure to circulating carboxypeptidase N, plasma profiles of the resulting isoforms are altered promptly and markedly after the release of new tissue isoenzymes. This paper reviews the results of experimental and preliminary clinical studies, showing the potential for rapid diagnosis of myocardial infarction and coronary artery recanalization by analysis of isoforms of CK isoenzymes in plasma.