What distinguishes a subendocardial myocardial infarction (MI)?

A subendocardial myocardial infarction specifically involves damage to the innermost layer of the heart muscle, known as the endocardium. This type of heart attack typically occurs when there is insufficient blood flow to this area, often due to narrowed coronary arteries, which can be a consequence of atherosclerosis or other cardiac conditions. In a subendocardial MI, the infarct does not penetrate through the entire thickness of the myocardium, instead affecting only the inner layer. This distinguishes it from other types of myocardial infarctions that involve different layers of the heart wall, such as epicardial or full-thickness (transmural) infarctions. Thus, recognizing that a subendocardial MI specifically targets the endocardial layer is crucial for proper diagnosis and treatment.