Myocardial ischemia is not always due to epicardial atheromatous disease.

Symptoms related to myocardial ischemia, for the most part, are due to high-grade epicardial coronary artery stenoses. However, in some instances at coronary angiography, no such lesions are seen to account for symptoms due to an imbalance between myocardial oxygen supply and myocardial oxygen demand. Thus, the finding of normal or nonobstructive epicardial coronary arteries at coronary angiography does not exclude the presence of myocardial ischemia in some patients.