CAN ATHEROSCLEROTIC CORONARY-ARTERIES VASODILATE - AN INTRAOPERATIVE HIGH-FREQUENCY EPICARDIAL ECHOCARDIOGRAPHIC STUDY

Our purpose was to evaluate the vasodilating responses of atherosclero tic coronary arteries using intraoperative high-frequency (12 MHz) epi cardial echocardiography. We obtained continuous high-frequency epicar dial echocardiographic recordings during surgery, and determined cross -sectional lumen area from 17 coronary arterial segments (12 patients) . Nitroglycerin (100 to 400 mu g/min) was administered intravenously t o reduce mean (+/-SEM) arterial pressure 14 +/- 1.8 mm Hg. The cross-s ectional arterial images were classified using 3 different parameters: arterial lumen area, percentage of the arterial wall circumference th at was atherosclerotic (wall thickness >0.7 mm), and presence of an ec centrically shaped arterial lumen (maximal/minimal luminal diameter >1 .5), Nine arterial segments had small (<5.0 mm(2)) arterial lumens (1. 7 +/- 0.40 mm(2) [+/- SEM; range 0.6 to 3.9]). With nitroglycerin, the luminal area increased 0.8 +/- 0.28 mm(2) (range 0 to 2.5), and 39 +/ - 12.1% (range 0 to 117). The remaining 8 segments had larger (greater than or equal to 5.0 mm(2)) lumens (8.7 +/- 0.91 mm(2) [range 5.0 to 11.9]). With nitroglycerin the luminal area increased 4.3 +/- 1.11 mm( 2) (range 1.4 to 11.4), and 51 +/- 10.2% (range 16 to 96). Seven arter ial 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 (max imal/minimal lumen diameters 1.3 +/- 0.04 [range 1.1 to 1.5]), nitrogl ycerin increased luminal area by 48 +/- 12.6% (range 0 to 117) (p = NS ). With regard to the percent arterial wall circumference that was ath erosclerotic, 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 s egments having primarily normal wall thickness (0% to 25% of circumfer ence was abnormally thickened >0.7 mm), where luminal area increased 3 8 +/- 8.5% (range 14 to 71). Thus, severely atherosclerotic coronary a rteries retain vasodilating ability. However, the absolute and/or perc ent Increase in luminal areas was often small, especially in the most severely diseased arteries.