🔹 Unstable Angina – Overview Unstable angina is a clinical syndrome under the spectrum of acute coronary syndromes (ACS) , caused by reduced blood flow to the heart due to partial obstruction of a coronary artery. It is a medical emergency . 🔹 Key Features Chest pain/discomfort at rest or with minimal exertion. New-onset angina (within the last 4–6 weeks, usually severe). Increasing frequency, duration, or severity of pre-existing angina (crescendo angina). Pain often lasts >20 minutes , not fully relieved by rest or nitroglycerin. May radiate to jaw, neck, left arm, or back. Associated symptoms: sweating, shortness of breath, nausea, palpitations, anxiety. 🔹 Pathophysiology Rupture or erosion of an atherosclerotic plaque . Platelet aggregation and non-occlusive thrombus formation. Leads to intermittent myocardial ischemia without necrosis (troponin negative). 🔹 Differentiation from Other ACS Unstable Angina (UA): No rise in...