Which statement is true about myocardial infarcts?

Which statement is true about myocardial infarcts?

• A. Most infarcts are transmural
• B. Most infarcts are subendocardial
• C. Infarcts are never transmural
• D. Infarcts are always subepicardial

Answer: (A)

Infarct patterns hinge on how completely a coronary artery is blocked and which myocardial layers are most vulnerable to ischemia. When a major epicardial artery is acutely occluded, the deprived myocardium necroses through the full thickness of the wall, producing a transmural infarct. The inner endocardial region is the most sensitive to ischemia because it has the highest metabolic demand and is furthest from the epicardial blood supply; if the occlusion persists, necrosis spreads from subendocardium outward, resulting in a transmural lesion. This is why transmural infarcts are common and often correlate with ST-elevation MI on ECG. Subendocardial infarcts occur when there isn’t complete occlusion, or in situations of global hypoperfusion or microvascular dysfunction, affecting only the inner portion of the wall. They are less common than transmural infarcts. The statements claiming infarcts are never transmural or always subepicardial are not correct, and saying most infarcts are subendocardial contradicts the typical pattern described above.

Infarct patterns hinge on how completely a coronary artery is blocked and which myocardial layers are most vulnerable to ischemia. When a major epicardial artery is acutely occluded, the deprived myocardium necroses through the full thickness of the wall, producing a transmural infarct. The inner endocardial region is the most sensitive to ischemia because it has the highest metabolic demand and is furthest from the epicardial blood supply; if the occlusion persists, necrosis spreads from subendocardium outward, resulting in a transmural lesion. This is why transmural infarcts are common and often correlate with ST-elevation MI on ECG.

Subendocardial infarcts occur when there isn’t complete occlusion, or in situations of global hypoperfusion or microvascular dysfunction, affecting only the inner portion of the wall. They are less common than transmural infarcts. The statements claiming infarcts are never transmural or always subepicardial are not correct, and saying most infarcts are subendocardial contradicts the typical pattern described above.