Can Atherosclerotic Coronary Arteries Vasodilate? An Intraoperative High-Frequency Epicardial Echocardiographic Study

Our purpose was to evaluate the vasodilating responses of atherosclerotic coronary arteries using intraoperativehigh-frequency (12 MHz) epicardial echocardiography. We obtained continuous high-frequency epicardial echocardiographic recordings during surgery, and determined cross-sectional lumen area from 17 coronary arterial segments (12 patients). Nitrogfycerin (100 to 400 μg/mfn) was administered intravenously to reduce mean (± SEM) arterial pressure 14 ± 1.8 mm Hg. The cross-sectional arterial images were classified using 3 different parameters: arterial lumen area, percentage of the arterial wall circumference that was atherosclerotic (wall thickness >0.7 mm), and presence of an eccentrically shaped arterial lumen (maximal/minimal luminal diameter >1.5). Nine arterial segments had small (< 5.0 mm2) arterial lumens (1.7 ± 0.40 mm2 [± SEM; range 0.6 to 3.9]). With nitroglycerin, the luminal area increased 0.8 ± 0.28 mm2 (range 0 to 2.5), and 39 ± 12.1% (range 0 to 117). The remaining 8 segments had larger (≥ 5.0 mm2) lumens (8.7 ± 0.91 mm2 [range 5.0 to 11.9]). With nitroglycerin the luminal area increased 4.3 ± 1.11 mm2 (range 1.4 to 11.4), and 51 ± 10.2% (range 16 to 96). Seven arterial segments had eccentric lumens; mean maximal/minimal ratio was 1.8 ± 0.08 (range 1.6 to 2.0). The area increased 39 ± 7.3% (range 16 to 71) with nitroglycerin. In the 10 concentrically shaped lumens (maximal/minimal lumen diameters 1.3 ± 0.04 [range 1.1 to 1.5]), nitroglycerin increased luminal area by 48 ± 12.6% (range 0 to 117) (p = NS). With regard to the percent arterial wall circumference that was atherosclerotic, 11 segments had 75% to 100% involvement of the arterial circumference (mean 96 ± 2.3%). Nitroglycerin increased luminal area by 48 ± 11.4% (range 2.3 to 117). Similar variability was seen in segments having primarily normal wall thickness (0% to 25% of circumference was abnormally thickened >0.7 mm), where luminal area increased 38 ± 18.5% (range 14 to 71). Thus, severely atherosclerotic coronary arteries retain vasodilating ability. However, the absolute and/or percent increase in luminal areas was often small, especially in the most severely diseased arteries.