“IT IS NOT A BENIGN DIAGNOSIS:” Microvascular Heart Disease. “While traditional coronary heart disease involves the buildup of plaque and resulting blockages in the large arteries that feed the heart muscle, microvascular heart disease affects the tiny branches or tributaries of these large vessels. Abnormalities in the endothelium, or inner lining, of these smaller vessels can cause spasms, resulting in pain and diminished blood flow to the heart.”