Final answer:
The subendocardium is the region of the myocardium that receives the least perfusion during systole due to the compression of the coronary vessels during the contraction of the ventricular myocardium.
Step-by-step explanation:
The region of the myocardium that receives the least amount of perfusion during systole is subendocardium. During systole, the heart's ventricles contract, ejecting blood into the aorta and pulmonary artery to supply the body and lungs with oxygenated blood. The contraction of the ventricular myocardium compresses the coronary vessels that run through it, notably affecting the subendocardial regions that are the innermost layer of the heart muscle and closest to the ventricular cavity. This compression leads to these areas receiving a reduced blood supply during systole.
When the ventricles relax during diastole, the subendocardium receives the majority of its blood flow; thus, conditions that decrease diastolic duration can lead to subendocardial ischemia. This is particularly important in clinical situations involving increased heart rates or compromised coronary artery flow.