Coronary artery constriction caused by the cold pressor test in human hypertension

Epicardial coronary arteries are not adequately sized in hypertensive patients

OBJECTIVES

This study sought to compare coronary artery dimensions in hypertensive patients and normal subjects.

BACKGROUND

Myocardial oxygen demand at rest and corresponding coronary blood flow are the main determinants of large coronary artery dimensions in humans. Coronary diameters are increased in aortic valve disease.

METHODS

Left main, proximal and distal left anterior descending and proximal circumflex coronary artery diameters were measured by quantitative angiography in 10 control subjects (group 1) and 26 untreated hypertensive patients, 12 without (group 2a) and 14 with (group 2b) left ventricular hypertrophy. All patients had normal cholesterol levels and angiographically normal coronary arteries. Measurements were made at baseline and after 2 mg of intracoronary isosorbide dinitrate to obtain maximal dimensions of vessels. Coronary flow velocity was measured in the distal left anterior descending coronary artery by Doppler ultrasound.

RESULTS

Despite a higher rate-pressure product in hypertensive patients, all segment diameters were slightly but not significantly higher at baseline in group 2b than in groups 1 and 2a. Diameters were similar in the three groups after isosorbide dinitrate. Conversely, coronary flow velocity was significantly higher in hypertensive patients than in group 1 either at baseline (10.4 +/- 2.2 [mean +/- SD] cm/s [group 2a] and 12.8 +/- 2.4 cm/s [group 2b] vs. 6.5 +/- 2.0 cm/s [group 1], all p < 0.001) or after isosorbide dinitrate (6.8 +/- 2.8 cm/s [group 2a] and 7.8 +/- 2.1 cm/s [group 2b] vs. 3.7 +/- 0.8 cm/s [group 1], p < 0.01 and p < 0.001, respectively).

CONCLUSIONS

Despite an elevated myocardial oxygen demand, maximal dimensions of large coronary arteries are not increased in hypertensive patients, resulting in an elevated coronary flow velocity that may increase longitudinal shear stress at the endothelial surface. This elevated flow velocity might be an important determinant in the pathogenesis of atherosclerosis in hypertensive patients.

Coronary artery response to cold-pressor test is impaired early after operation in heart transplant recipients

OBJECTIVES

The aim of the present study was to evaluate the coronary vasomotor response to the cold-pressor test within 3 months after heart transplantation.

BACKGROUND

Normal epicardial coronary arteries dilate in response to sympathetic stimulation evoked by the cold-pressor test. In transplant recipients, abnormal coronary vasomotion has been described shortly after operation.

METHODS

Fourteen heart transplant recipients were compared 52 +/- 15 days (mean +/- SD) after operation with 10 control subjects. All had angiographically normal epicardial coronary arteries. Coronary blood flow velocity was measured with a Doppler catheter placed in the proximal left anterior descending coronary artery. Four segments in each patient were analyzed by quantitative coronary angiography to assess the diameter changes during the cold-pressor test and after intracoronary injection of isosorbide dinitrate.

RESULTS

Coronary flow velocity increased similarly during the cold-pressor test in control subjects and in transplant recipients, from 7.5 +/- 2.3 to 11.0 +/- 3.9 cm/s and from 10.3 +/- 3.2 to 13.7 +/- 4.8 cm/s (both p < 0.01). In control subjects, 39 of 40 segments analyzed dilated during the cold-pressor test. In transplant recipients, 48 of 56 segments analyzed did not change or constricted. The mean epicardial coronary diameter increased significantly during the cold-pressor test in control subjects (+13 +/- 6%, p < 0.001), whereas it did not change significantly in transplant recipients (-2 +/- 9%, p = NS). In transplant recipients, isosorbide dinitrate elicited coronary vasodilation similar to that in control subjects.

CONCLUSIONS

These data indicate that in human transplanted denervated hearts, coronary vasodilation in response to sympathetic stimulation by cold exposure is impaired shortly after operation.

Loss of flow-dependent coronary artery dilatation in patients with hypertension

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.