Acute coronary syndrome (ACS) refers to any constellation of clinical symptoms that are compatible with acute myocardial ischemia. ACS is divided into ST- elevated myocardial infarction (STEMI), non-ST elevated myocardial infarction (NSTEMI), and unstable angina (UA). STEMI results from complete and prolonged occlusion of an epicardial coronary blood vessel and is defined based on ECG criteria..NSTEMI usually results from severe coronary artery narrowing, transient occlusion, or microembolization of thrombus and/or atheromatous material. NSTEMI is defined by an elevation of cardiac biomarkers in the absence of ST elevation. The syndrome is termed UA in the absence of elevated cardiac enzymes. History, physical examination, ECG, biochemical markers, ECHO all remain important tools to make an appropriate diagnosis The management of ACS should focus on rapid diagnosis, risk stratification, and institution of therapies that restore coronary blood flow and reduce myocardial ischemia.