Coronary atherosclerosis: extending to the microcirculation?

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This editorial refers to ‘Coronary microcirculatory vasodilator function in relation to risk factors among patients without obstructive coronary disease and low to intermediate Framingham risk score’[†][1], by R. Rubinshtein et al. on page 936 The coronary circulation, responsible for the delivery of oxygen and other nutrients to the myocardium, is a complex system of conductance and resistance vessels. Each has its own mechanisms of dynamic regulation of its calibre through changes in the contractile state of the underlying smooth muscle. In addition, each plays a different role in determining myocardial perfusion in health and disease. The larger epicardial coronary arteries normally offer no significant resistance to blood flow and thus contribute little to the adaptive response of the coronary circulation to the physiological changes in myocardial oxygen demands that occur, for example, during exercise. However, they are the site for the development of coronary atherosclerosis, the best known and most dreaded form of ischaemic heart disease. That atherosclerotic obstructions of the epicardial coronary arterial lumen contribute to the occurrence of myocardial ischaemia and necrosis is easily demonstrable and well accepted. In fact, the diagnosis of ‘coronary artery disease’ is conventionally applied only to patients who are shown to have significant narrowing of one or more major epicardial coronary artery. Although controversies persist regarding their optimal utilization, there is a large armamentarium of therapies available to treat patients with severely narrowed epicardial coronary arteries. These include multiple medications, and percutaneous and surgical revascularization, in many instances supported by the results of randomized clinical trials demonstrating their relative efficacy. The smaller coronary arteries (i.e. too small in calibre to be visualized by angiography) constitute the coronary microcirculation and are those that normally offer significant vascular resistance. Consequently, it is the changes in the calibre of these smaller vessels that determine coronary blood … *Corresponding author. Tel: +1 202 877 9090, Fax: +1 202 877 9034, Email: julio.a.panza{at}medstar.net [1]: #fn-1