True or false: Most infarcts are transmural.

True or false: Most infarcts are transmural.

• A. False
• B. True
• C. Sometimes
• D. Never

Answer: (B)

Most infarcts in the heart are transmural because a sudden, complete blockage of a coronary artery deprives all layers of the myocardium in that territory of blood flow. The inner subendocardial region is the most vulnerable to ischemia, so necrosis begins there and, if the occlusion persists, extends through the full thickness of the wall, producing a transmural (full-thickness) infarct. This pattern underlies the classic ST-segment elevation MI on ECG and the typical wedge-shaped, pale area seen on gross pathology. Subendocardial infarcts occur when perfusion is only partially reduced or when collateral blood flow limits necrosis, so only the inner layers are affected. Thus, the statement that most infarcts are transmural aligns with how complete arterial occlusion generally produces full-wall necrosis.

Most infarcts in the heart are transmural because a sudden, complete blockage of a coronary artery deprives all layers of the myocardium in that territory of blood flow. The inner subendocardial region is the most vulnerable to ischemia, so necrosis begins there and, if the occlusion persists, extends through the full thickness of the wall, producing a transmural (full-thickness) infarct. This pattern underlies the classic ST-segment elevation MI on ECG and the typical wedge-shaped, pale area seen on gross pathology. Subendocardial infarcts occur when perfusion is only partially reduced or when collateral blood flow limits necrosis, so only the inner layers are affected. Thus, the statement that most infarcts are transmural aligns with how complete arterial occlusion generally produces full-wall necrosis.