Angina pectoris is chest pain or discomfort caused by myocardial ischemia — a mismatch between myocardial oxygen supply and demand — without myocardial necrosis. It is the clinical presentation of obstructive coronary artery disease (CAD) and a major warning sign for impending myocardial infarction. Because angina and MI share the same pain, the distinguishing feature is the absence of myocardial cell death: troponin is negative in angina. Three main types: - Stable angina: predictable, provoked by exertion or emotional stress and relieved by rest or nitroglycerin within about 5 minutes; caused by fixed atherosclerotic stenosis. - Unstable angina (a form of acute coronary syndrome): new-onset pain, pain at rest, increasing frequency or severity, or pain not relieved by three nitroglycerin doses; caused by plaque rupture with partial occlusion; a medical emergency that lies on a continuum with NSTEMI. - Prinzmetal (variant or vasospastic) angina: occurs at rest, often at night, caused by coronary artery spasm, with transient ST elevation during attacks; treated with calcium channel blockers and nitrates, NOT beta-blockers. Angina is extremely common in US adults with CAD, and...