What is the underlying process that typically causes an acute myocardial infarction?

• A. Vasospasm of a coronary artery without plaque rupture
• B. Occlusion due to embolism from a distant source
• C. Atherosclerotic plaque rupture with thrombosis causing occlusion of a coronary artery
• D. Spasm of a coronary artery due to cocaine use

Answer: (C)

The main process behind most acute myocardial infarctions is rupture of an atherosclerotic plaque in a coronary artery with subsequent thrombosis that occludes the vessel. When a vulnerable plaque with a lipid-rich core and a thin fibrous cap tears, tissue factors and exposed collagen trigger rapid platelet adhesion and activation, and the coagulation cascade accelerates to form a thrombus. If the thrombus grows or lodges at the site, it can completely block blood flow to the myocardium supplied by that artery, causing ischemia and then infarction.

Other mechanisms exist—vasospasm can cause ischemia and chest pain, and emboli from other sites can rarely lodge in a coronary artery—but the typical underlying event in an acute myocardial infarction is plaque rupture with thrombosis leading to occlusion.