Coronary Physiology and Atherosclerosis

The coronary vasculature has been traditionally divided into three functional groups: large conductance vessels visible on coronary angiography, which offer little resistance to blood flow; small resistance vessels ranging in size from about 250 to 10 μm in diameter; and veins. Although it has been taught that arterioles (precapillary vessels < 50 μm) account for most of the coronary resistance, studies indicate that, under resting conditions, 45% to 50% of total coronary vascular resistance resides in vessels larger than 100 μm in diameter. This may be due, in part, to the relatively great length of the small arteries.