Background: Abnormal endothelium-dependent coronary response to acetylcholine has been shown in patients with essential hypertension. We tested the hypothesis that flow-dependent dilatation, which has been shown in normal human coronary arteries, is impaired in hypertensive patients.
Methods and results: The coronary vasomotor response to maximal increase of blood flow induced by papaverine was studied in 10 control subjects and in 14 hypertensive patients with no other risk factors and angiographically normal coronary arteries. After the injection of papaverine in the midportion of the left anterior descending coronary artery (LAD), the diameter of the proximal LAD (LAD1) was measured by quantitative angiography, whereas that of the proximal circumflex artery (LCx) served as control segment. Estimates of coronary blood flow in the distal LAD (LAD2) were calculated by intracoronary Doppler flow velocity measurements. An increase in LAD2 blood flow of 521 +/- 41% (P < .001) in control subjects was associated with a 17.0 +/- 3.3% dilatation of the LAD1 (P < .001) and with no significant change in the diameter of the LCx. In hypertensive patients, despite a comparable increase in LAD2 blood flow of 406 +/- 32% (P < .001), the LAD1 failed to dilate (-0.4 +/- 0.6%, NS). The dilative response to isosorbide dinitrate was similar in control subjects and hypertensive patients (30.0 +/- 4.1%, P < .001 and 21.9 +/- 1.9%, P < .001, respectively).
Conclusions: Thus, the flow-mediated coronary dilatation is lost in hypertensive patients, and this may impair normal dilatation observed in response to an increase in myocardial metabolic demand.