Effects of coronary atherosclerosis on coronary reserve

Abstract

To assess the physiologic significance of coronary obstructions in patients at the time of open-heart surgery we have studied coronary reactive hyperemic responses to a 20-second coronary occlusion. Coronary blood flow velocity was measured with a single crystal pulsed-Doppler probe coupled to the surface coronary vessel with a small suction cup. Our studies have demonstrated that normal vessels supplying a normal myocardium increase coronary blood flow velocity 5–6 fold following release of a 20-second coronary occlusion. Furthermore, patients with severe coronary obstructions (greater than 90% diameter narrowing) have markedly blunted reactive hyperemic responses (i.e. less than a two-fold increase in coronary blood flow velocity following release of a 20-second coronary occlusion). In patients with obstructions of intermediate severity (10–90% diameter narrowing) the relationship between percent stenosis and the reactive hyperemic response was poor. In other studies, we have shown that the measurement of absolute cross-sectional area of a lesion with quantitative coronary angiographic techniques allows a better separation of patients with normal and abnormal coronary reserve than the use of percent stenosis. These studies emphasize the futility of utilizing percent stenosis to assess the physiologic significance of coronary obstructions in patients with atherosclerosis, particularly when the coronary obstructive lesions are of intermediate severity (10–90% diameter stenosis).