COMPARISON OF THE EFFECTS OF EXERCISE AND COLD PRESSOR TEST ON THE VASOMOTOR RESPONSE OF NORMAL AND ATHEROSCLEROTIC CORONARY-ARTERIES AND THEIR RELATION TO THE FLOW-MEDIATED MECHANISM

This study was designed to assess the vasomotor response of coronary a rteries to exercise and the cold presser test, and its relationships w ith the endothelium-mediated dependent mechanism. Twenty-two patients were entered in the study. Group 1 was composed of 12 patients with a total cholesterol level <200 mg/dl associated with angiographically sm ooth, normal coronary arteries. Group 2 consisted of 10 patients with a cholesterol level >240 mg/dl and angiographic luminal irregularities of the left anterior descending coronary artery. Coronary blood flow was assessed by a 0.018-inch tip guidewire during Doppler ultrasonogra phy, and analysis of the coronary arterial dimension of the midportion of the left anterior descending coronary artery was performed by quan titive coronary angiography. Catecholamine concentrations were assesse d at the different stages of the protocol. The rate-pressure product i ncreased during both the cold presser test and exercise (p <0.001). Co ronary blood flow velocity increased during the cold presser and exerc ise tests by 24.5 +/- 10% and 72 +/- 42%, respectively (p <0.001), and by 127 +/- 62% (p <0.0001) after administration of papaverine. In gro up 1, the cold presser test had a more pronounced vasodilating effect on epicardial coronary arteries (+11.2 +/- 16%) compared with group 2 (-2 +/- 9%, p <0.05). Similarly, exercise had a vasodilating action in group 1 (11.3 +/- 15%)compared with group 2 (-1.9 +/- 8%, p <0.05). B oth responses were highly correlated (r = 0.92, p <0.001). Papaverine administration had a vasodilating action in patients from group 1 (11. 6 +/- 16%) compared with group 2 (-1.2 +/- 8%, p <0.05). Both the vaso motor responses to the cold presser test and exercise were correlated to the response to papaverine administration, r = 0.90 and r = 0.92, r espectively (all p <0.001). Noradrenaline concentrations increased bot h during the cold pressor test and exercise (p <0.05), but not after p apaverine administration. These results show that the endothelium modu lates the response of epicardial coronary arteries to sympathetic stim ulation, mainly by a flow-mediated mechanism.