What area of the myocardium is most vulnerable to ischemia?

The left ventricular subendocardium is indeed the area of the myocardium that is most vulnerable to ischemia. This susceptibility is primarily due to its anatomical and physiological characteristics.

The subendocardial layer, which lies just beneath the endocardium, receives its blood supply from the epicardial coronary arteries. Because of this positioning, it is the furthest from the arterial supply, making it more susceptible to reduced blood flow, particularly during times of increased demand, such as during myocardial ischemia.

In conditions such as decreased perfusion pressures or increased myocardial oxygen demand, the subendocardium is often the first to become ischemic. This is due to the fact that during diastole, when coronary blood flow occurs, the pressure in the left ventricle can compress the subendocardial vessels, thereby limiting their blood supply further.

In contrast, the other areas mentioned, including the left ventricular epicardium and the right ventricular myocardium, have relatively better perfusion and are less vulnerable to ischemia under similar stress conditions. Therefore, acknowledging the unique anatomical features of the left ventricular subendocardium helps understand its heightened risk for ischemic conditions.