What is the primary cause of acute coronary syndrome?

• A. Sympathetic stimulation
• B. Cor pulmonale
• C. Atherosclerosis
• D. Cardiac arrhythmias

Answer: (C)

The central idea is that acute coronary syndrome stems from plaque instability in a coronary artery. A vulnerable atherosclerotic plaque can rupture or erode, exposing thrombogenic material and triggering rapid platelet activation and clot formation. The resulting thrombus narrows or blocks blood flow, creating myocardial oxygen shortage and chest pain, which may progress to a full heart attack if the occlusion is complete and lasting. This mechanism explains the spectrum of ACS—from unstable angina to NSTEMI and STEMI—depending on how much flow is restored or blocked and how long the tissue is deprived.

Sympathetic stimulation can raise heart rate and oxygen demand and might precipitate symptoms, but it’s not the root cause of ACS. Cor pulmonale is a separate condition related to right heart failure from lung disease. Cardiac arrhythmias can accompany ischemia but are not the primary initiating event of ACS.