EFFECT OF PLAQUE BURDEN ON CORONARY VASOREACTIVITY IN EARLY ATHEROSCLEROSIS

Coronary atherosclerosis, during its initial stages of development, ma y result in abnormal endothelium-dependent vasomotor responses. The re lation between the degree of vasoreactivity and the amount of atheroma tous plaque load has not been decisively determined. The aim of the pr esent study was to investigate the effects of segmental plaque burden on endothelium-dependent and independent coronary stimulation. We stud ied 37 individual coronary segments along the course of coronary arter ies that had angiographically either nonvisible or nonobstructive athe romatous lesions. Endothelium-dependent and independent stimulation of each segment from 10 patients with known significant coronary artery disease was examined with intracoronary administrations of normal sali ne, acetylcholine 10(-6) M and 10(-5) M, and nitroglycerin, respective ly, using quantitative coronary angiography. Simultaneous vasomotor ef fects on the microcirculation were evaluated by a Doppler guidewire (F lowire). Subsequently, intracoronary ultrasound was used at each segme nt for detailed morphometric and composition analysis. By quantitative coronary angiography, when compared with normal saline, acetylcholine produced a reduction in minimal lumen diameter of 15.2 +/- 25.6%, and nitroglycerin produced an increase of 18.0 +/- 22.5%. The degree of v asoconstriction induced by acetylcholine correlated inversely (r = 0.5 1, p = 0.001) to the amount of segmental maximal plaque thickness. No relation between the response to nitroglycerin and the parameters obta ined by intracoronary ultrasound was documented. Fibrous coronary plaq ues showed less vasomotor changes than plaques with mixed echogenicity , probably due to a significantly larger plaque burden. Acetylcholine produced overall a differential vasomotor response in the epicardial s egments (vasoconstriction) compared with the microcirculation (vasodil ation). These results indicate that in early atheromatous coronary les ions, the degree of endothelium-dependent vasoconstrictive response is inversely related to the amount of segmental plaque burden. (C) 1998 by Excerpta Medica, Inc.