Myocardial infarction is caused by what?

• A. Coronary thrombosis that stops blood flow.
• B. Viral infection.
• C. Allergic reaction.
• D. Low blood sugar.

Answer: (A)

Myocardial infarction happens when blood flow to a part of the heart is suddenly blocked, so heart muscle tissue is starved of oxygen and begins to die. The usual trigger is a coronary thrombosis that occludes a coronary artery, typically at the site of a ruptured atherosclerotic plaque. When the plaque ruptures, it exposes material that promotes clot formation, and a fast-forming thrombus can completely block the artery, stopping oxygen delivery to the heart muscle beyond that point.

The other options don’t fit the typical mechanism: a viral infection can cause myocarditis rather than a sudden blockage of a coronary artery; an allergic reaction can cause various systemic effects and, in rare cases, coronary spasm, but it’s not the standard cause of a myocardial infarction; low blood sugar affects energy availability but does not directly block coronary blood flow.