The proximal segments of the main coronary vessels are the most often localization of "soft" unstable atherosclerotic plaques. The maximum number of plaques developed in the anterior descending branch of the left coronary artery. Pathognomonic relationship was found between the type of these plaques (with ulceration, rupture, thrombosis) and certain acute coronary syndrome. It was shown that the criteria of the plaque instability correlated with clinical manifestations of coronary syndromes. The bases and effects of "pathological" vascularization of unstable atherosclerotic plaques on the angioarchitectonics and hemodynamics of the heart were determined. Dissociation between myocardial vascularization degree and myocardial blood supply index was detected, which underlies the development of "unstable" myocardium in patients with acute coronary syndromes.