ABNORMAL ENDOTHELIUM-DEPENDENT CORONARY VASOMOTION IN HYPERTENSIVE PATIENTS

Coronary vasomotion is abnormal in hypertensive patients, as evidenced by reduced coronary vasodilator reserve, but endothelium-dependent coronary vasomotion in hypertensive patients has not been studied. To assess the integrity of endothelium-dependent vasodilation, the response of coronary arteries to acetylcholine (an endothelium-dependent vasodilator) and nitroglycerin (an endothelium-dependent vasodilator) was studied in 14 patients undergoing cardiac catheterization. Eight patients with essential hypertension were compared with six normotensive patients. None had obstructive disease detectable by coronary arteriography. Coronary artery diameter was measured with digital-subtracted arteriography and coronary blood flow velocity with a Doppler flow velocity catheter. At baseline, coronary artery diameter was similar in the hypertensive and the normotensive control patients (2.4 +/- 0.3 vs. 2.8 +/- 0.7 mm). During intracoronary acetylcholine infusion (30-mu-g/min), coronary artery diameter decreased to 1.3 +/- 0.7 mm in the hypertensive patients (p < 0.005), but was unchanged (2.7 +/- 0.8 mm) in the normotensive patients. With intracoronary nitroglycerin (200-mu-g), coronary artery diameter increased significantly in both groups. Calculated coronary blood flow decreased during acetylcholine infusion by 59 +/- 31% in the hypertensive patients but increased by 3 +/- 3% in the normotensive group (p < 0.005). There was a significant negative correlation between the percent change in estimated coronary blood flow during acetylcholine infusion and mean arterial pressure measured at baseline (r = 0.67, p < 0.02). Therefore, these hypertensive patients exhibited marked coronary vasoconstriction in response to intracoronary acetylcholine but normal vasodilation in response to nitroglycerin, suggesting abnormal endothelium-dependent vasodilation. The latter may be a mechanism contributing to reduced coronary vasodilator reserve and angina pectoris in hypertensive patients.