Acute Coronary Syndromes: Introduction and Pathophysiologic Classification

Abstract

Several different classifi cations of acute coronary syndromes (ACS) exist, and most of them are based on the electrocardiogram (ECG). Based on differences in pathophysiology, treatment, and outcome, ACS are classifi ed as ST-elevation myocardial infarction (STEMI), non-ST-elevation MI, and unstable angina. STEMI is the most urgent subtype of ACS, because it is believed to refl ect acute ongoing transmural myocardial ischemia caused by acute coronary occlusion. Based on changes in the different parts of the ECG, ACS patients may be classifi ed according to the extent of the ischemic process or myocardial injury, the acuteness of the disease process, and the severity of myocardial ischemia. In the majority of patients, ACS classifi cation is rather straightforward, but some controversial issues remain to be solved in the future. The role of different ACS subtypes regarding choice of medication also needs to be explored more in detail. This chapter reviews pathophysiological mechanisms explaining the different ECG patterns encountered in ACS; the different ECG manifestations are also presented by illustrative fi gures. Both established guidelines and ECG-based expert reports for the classifi cation of ACS are presented. Unresolved, controversial issues regarding ECG manifestations of ACS are discussed.