Effect of angiotensin type 1 receptor blockade on coronary vasomotion assessed by ¹⁵O-water PET in patients with hypertension

Abstract

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Objectives: Coronary vasomotion is impaired in patients with essential hypertension at early stage. Increased attention is given to developing strategies that target coronary vasomotor function in the treatment of hypertension. Angiotensin type 1 receptor blockade (ARB) could have a beneficial effect on coronary vasomotion. Thus, we evaluated the effects of long-term ARB treatment on coronary endothelial function assessed by ¹⁵O-water PET in patients with hypertension.

Methods: This study included ten patients with untreated essential hypertension without left ventricular hypertrophy (mean age 48±15 years old) and ten age-matched healthy controls. MBF was measured non-invasively with ¹⁵O-water PET at rest, during cold pressor test (CPT) at baseline and after 12 weeks of ARB olmesartan (mean 27±14 mg per day) treatment. Coronary vascular resistance (CVR) was calculated by dividing the mean blood pressure by MBF for correcting the effect of blood pressure. CPT-induced MBF changes (ΔMBF) and CVR during CPT (CPT-CVR) were used as a marker of coronary endothelial function.

Results: Left ventricular mass index, blood sugar and total cholesterol were similar between the two groups. At baseline, ΔMBF in patients was lower, and CPT-CVR was higher than those in healthy controls (0.00±0.23 vs. 0.31±0.17 ml/g/min, 119±30 vs. 88±16 mmHg/ (ml/g/min); respectively, p<0.01). After ARB treatment, resting blood pressure in patients significantly decreased (146±11/98±18 vs. 124±11/79±14 mmHg; p<0.01). ΔMBF and CPT-CVR in patients were significantly improved to the comparable level of those in control subjects (0.28±0.20 ml/g/min; p<0.01 vs. baseline, 97±27 mmHg/ (ml/g/min); p<0.05 vs. baseline, respectively).

Conclusions: Long-term ARB therapy in patients with hypertension restores ΔMBF and CPT-CVR, indicating that ARB olmesartan has a beneficial effect on coronary vasomotion. Furthermore, ¹⁵O-water PET provides useful information to monitor the effects of medical intervention on coronary vasomotor function non-invasively.