Acute coronary syndrome

Acute coronary syndrome (ACS) is a syndrome (a set of signs and symptoms) due to decreased blood flow in the coronary arteries such that part of the heart muscle is unable to function properly or dies. The most common symptom is centrally located pressure-like chest pain, often radiating to the left shoulder or angle of the jaw, and associated with nausea and sweating. Many people with acute coronary syndromes present with symptoms other than chest pain, particularly women, older people, and people with diabetes mellitus.

Acute coronary syndrome is subdivided in three scenarios depending primarily on the presence of electrocardiogram (ECG) changes and blood test results (a change in cardiac biomarkers such as troponin levels): ST elevation myocardial infarction (STEMI), non-ST elevation myocardial infarction (NSTEMI), or unstable angina. STEMI is characterised by complete blockage of a coronary artery resulting in necrosis of part of the heart muscle indicated by ST elevation on ECG, NSTEMI is characterised by a partially blocked coronary artery resulting in necrosis of part of the heart muscle that may be indicated by ECG changes, and unstable angina is characterised by ischemia of the heart muscle that does not result in cell injury or necrosis.

ACS should be distinguished from stable angina, which develops during physical activity or stress and resolves at rest. In contrast with stable angina, unstable angina occurs suddenly, often at rest or with minimal exertion, or at lesser degrees of exertion than the individual's previous angina ("crescendo angina"). New-onset angina is also considered unstable angina, since it suggests a new problem in a coronary artery.