Myocardial infarction is caused by which mechanism?

• A. A coronary thrombosis - stopping blood flow.
• B. Bacterial infection.
• C. Autoimmune reaction.
• D. Dehydration.

Answer: (A)

The key idea is that a myocardial infarction results from an acute blockage of a coronary artery, most often caused by a thrombus forming on an atherosclerotic plaque. That clot stops blood flow to a section of heart muscle, so that tissue is deprived of oxygen and begins to die if flow isn’t restored. This is why the mechanism described as a coronary thrombosis that stops blood flow best explains MI.

The other options don’t fit this mechanism: bacterial infection can affect the heart in conditions like endocarditis or myocarditis but isn’t the direct cause of the typical acute blockage; an autoimmune reaction can inflame heart tissue but doesn’t normally produce the sudden arterial occlusion seen in MI; dehydration affects circulating volume but doesn’t by itself create the abrupt occlusion of a coronary artery.