Background: Coronary endothelial function is frequently studied by measuring the vasodilator response of coronary arteries to acetylcholine or to cold pressor test by invasive quantitative coronary angiography. Because invasive methods have substantial inherent limitations, studies should attempt to evaluate coronary endothelial function noninvasively.
Hypothesis: We attempted to evaluate the accuracy of measurement of the percent change in diameter of the left main trunk induced by cold pressor test with two-dimensional (2-D) echocardiography. Furthermore, we applied this method to the evaluation of coronary artery endothelial function in hypertensive patients.
Methods: We measured the left main trunk diameter in 21 subjects (51 +/- 4 years) before and after cold pressor test using quantitative coronary angiography followed immediately by 2-D echocardiography. The accuracy of measurement of the left main trunk diameter and its percent change by echocardiography was evaluated by comparing the values obtained by the two methods. In addition, using echocardiography, we compared left main trunk diameter responses to cold pressor test in 16 hypertensive patients [51 +/- 5 years (mean +/- standard deviation)] and 16 matched healthy subjects (50 +/- 4 years).
Results: Although there was only a weak correlation between the absolute values of the left main trunk diameter measured by the two methods (r = 0.61; p = 0.04), a strong correlation was found between the percent change in diameter measured by the two methods (r = 0.93; p = 0.0001). The percent change in diameter of the left main trunk induced by cold pressor test in hypertensive patients (-3.7 +/- 10.6%) was significantly lower than that in control subjects (13.2 +/- 6.8%, p = 0.0001).
Conclusions: Percent change in diameter of the left main trunk induced by cold pressor test can be evaluated accurately using 2-D echocardiography. Our study showed reduced vasodilation or vasoconstriction of the left main trunk after cold pressor test in hypertensive patients compared with healthy subjects, indicating impaired coronary endothelial function in hypertensive patients. The present echocardiographic method is a potentially useful new noninvasive method for evaluating coronary endothelial function.