What is the most common cause of myocardial infarction?

• A. Viral infection
• B. Spasm
• C. Trauma
• D. Blood clot in an artery narrowed by plaque

Answer: (D)

The most common cause of a myocardial infarction is a blood clot forming in a coronary artery that is already narrowed by atherosclerotic plaque. When a vulnerable plaque ruptures, its exposed contents trigger the clotting process—platelets adhere and aggregate, and a fibrin-rich thrombus forms. This thrombus often occludes the artery, abruptly stopping blood flow to a region of heart muscle and causing infarction. This mechanism is why treatments focus on antiplatelet and anticoagulant therapy and rapid reperfusion to restore blood flow. Other scenarios like viral myocarditis, coronary vasospasm, or trauma can cause heart injury, but they account for far fewer cases of MI and don’t reflect the predominant path to obstruction and tissue death.