Acute coronary syndrome and myocardial infarct--new definitions

Abstract

Until recently a general consensus existed for the clinical entity diagnosed as myocardial infarction using the world health organisation (WHO) definition. According to the WHO definition myocardial infarction was defined by a combination of two of three typical characteristics: typical symptoms, rise of cardiac enzymes (CK, CK-MB), and a typical ECG pattern involving the development of Q waves. New insights into the development of acute myocardial infarction, the superiority of the biochemical characteristics of cardiac troponin assays over CK and CK-MB measurements in blood, and new therapeutic concepts made a new definition of myocardial infarction, e.g. of the acute myocardial infarction, necessary. Timing of the diagnosis of myocardial necrosis is of outmost importance relative to the time of observation (acute, evolving, healing, healed MI), as is the classification of the extent of myocardial damage (microscopic, small, medium or large). The term "acute coronary syndrome" (ACS) has been established as a working diagnosis for choosing the appropriate therapeutic strategy. In patients with ACS and ST elevation ischemia (STEMI ACS, true posterior ischemia inclusive) as well as in patients with presumably new LBBB, immediate reperfusion therapy should be performed (primary PTCA or thrombolytic therapy), whereas in patients with ECG changes other than ST elevation or new LBBB (NSTEMIACS) additional antiplatlet therapy on top of aspirin and heparin is indicated. In contrast to the acute phase of infarction when troponin in blood often is not detectable yet, the diagnosis of definitive myocardial infarction is based primarily on troponin elevation. Hard criteria for established infarction are the development of pathologic Q waves or healing or healed myocardial necrosis in pathology; troponin may be normal then, depending of time relapsed.