“There are three main types of ischemic heart disease: obstructive coronary artery disease; nonobstructive coronary artery disease; and coronary microvascular disease. Coronary artery disease affects the large arteries on the surface of the heart and many people have both obstructive and nonobstructive forms of this disease. Coronary microvascular disease affects the tiny arteries in the heart muscle. It may occur with or without coronary artery disease.” https://www.nhlbi.nih.gov/health-topics/ischemic-heart-disease