HETEROGENEOUS VASOMOTOR RESPONSES OF CORONARY CONDUIT AND RESISTANCE VESSELS IN HYPERTENSION

Objectives. The purpose of our study was to investigate the relation b etween conductance and resistance coronary vasomotor responsiveness in hypertensive patients without atherosclerosis. Background. Although s imilar in morphology, conduit and resistance coronary vessels differ i mportantly in size, function and local environment and appear to be di fferentially affected in certain disease processes, such as atheroscle rosis and hypertension, However, little is known about the effect of h ypertension on contiguous coronary conduit and resistance vessels in h umans. Methods. Changes in coronary blood flow (a measure of resistanc e vessel reactivity) and coronary artery diameter (a measure of condui t vessel reactivity) were investigated in response to graded infusion of the endothelium-dependent agonist acetylcholine (ACh) in 98 patient s with normal coronary arteries. Results. In 31 normotensive, euglycem ic patients, conduit and resistance coronary artery responses to intra coronary infusion of ACh were significantly correlated (r = 0.73, p = 1 x 10(-6)), although eight patients (26%) had constriction of conduit but dilation of resistance arteries at peak effect, In 28 hypertensiv e patients without left ventricular hypertrophy (LVH), conduit and res istance artery responses to ACh remained significantly correlated (r = 0.5, p = 0.006), although 12 patients (43%) had discordant findings, Finally, in 39 hypertensive patients with LVH, conduit and resistance artery responses to ACh displayed the lowest correlation (r = 0.38, p = 0.02), with 22 patients (56%) demonstrating conduit artery constrict ion and resistance artery dilation. Conclusions. Despite angiographica lly normal coronary arteries, heterogeneous vasomotor responses (dilat ion and constriction) were demonstrated in contiguous conduit and resi stance arteries in normotensive and hypertensive patients referred for cardiac catheterization because of chest pain, In addition to more se vere endothelial dysfunction among conduit and resistance arteries, a greater frequency of discordant conduit and resistance artery response s and resistance vessel constriction was found with increasing severit y of hypertension, Our study suggests differing mechanisms of endothel ium responsiveness to ACh among conduit and resistance coronary arteri es. (C) 1998 by the American College of Cardiology.