In normal people, coronary arteries dilate in response to sympathetic stimulation evoked by the cold pressor test. Similarly, in normal coronary arteries the increase in blood flow velocity induced by papaverine results in flow-dependent coronary dilation.
To assess the coronary responses to both stimuli in hypertensive patients, variations of coronary artery diameters measured on proximal left anterior descending coronary arteries and coronary blood flow velocity were measured using quantitative coronary angiography and intracoronary Doppler in 10 controls and 12 hypertensive patients. All participants had angiographically normal coronary arteries. Total serum cholesterol, triglycerides, high-density Upoprotein and low-density lipoprotein cholesterol were within the normal range in all participants. None smoked or had diabetes mellitus.
During the cold pressor test (hands immersed in iced water for 120s), the rate-pressure product and coronary blood flow velocity increased respectively by 33±9% (P<0.001) and 51±26% (P<0.05) in controls and by 28±18% (P<0.001) and 68±52% (P<0.05) in hypertensive patients. Coronary arteries dilated by +12.0±4.4% (P<0.001) in controls and constricted by −10.3±8.5% (P<0.001) in hypertensive patients. After injection of 10 mg papaverine into the distal left anterior descending coronary artery, proximal left anterior descending coronary artery dilated by +17.0±10.6% (P<0.001) in controls and did not vary (-0.7%±10.6%) in hypertensive patients when blood flow velocity was increased respectively by 449±97% and 383±103% (P<0.001 in both groups). After 2mg isosorbide dinitrate, an endothelium-independent coronary dilator, selectively injected into the left coronary artery, dilation was similar in the two groups (+30.0±12.9% in controls, +22.3±7.5% in hypertensive patients, P<0.001 in both groups).
Coronary response to sympathetic stimulation and flow velocity endothelium-dependem coronary vasodilation are both impaired in hypertensive patients with angiographically normal coronary arteries.