Background A reduction in the density of capillaries (rarefaction) is known to occur in many tissues in patients with essential hypertension (HTN) and plays a crucial role in increasing peripheral resistance and blood pressure (BP). The aim of this clinical trial was to assess in a controlled, double blind, placebo-controlled design the effects of treatment of HTN with candesartan or amlodipine on microvascular rarefaction and other indices of vascular function in individuals with mild-to-moderate essential HTN.

Methods The capillary microcirculation was studied using the well-validated intravascular microscopy technique. After a 2-week single-blind placebo run-in period, patients who remained hypertensive (systolic BP 140–180 mmHg and/or diastolic BP 90 –110 mmHg) were randomised to 8-weeks treatment with either candesartan 8 mg daily (with forced titration to 16mg after 2 weeks) or amlodipine 5 mg orally daily (with forced titration to 10 mg after 2 weeks). Other vascular measurements included pulse wave velocity with Complior machine, central BP and Aortic Augmentation Index measurements with Omron HEM-9000AI machine.

Results Treatment with candesartan and amlodipine significantly reduced both brachial and central BP at 4 and 8 weeks (mean change -19.0 mmHg; 95% CI -−11.1 to -−26.9, p < 0.0001), and to 8 weeks active treatment (mean change -26.3 mmHg; 95% CI −17.5 to −35.0, p < 0.0001) but had no significant effect on basal (functional) or maximal (structural) capillary densities. Both drugs also reduced central BP and Aortic augmentation index significantly after 4 and 8 weeks but there was no significant changes in PWV.

Conclusions The study confirms that 8 weeks treatment with either candesartan or amlodipine significantly reduces radial and central BP in essential HTN but may not be a sufficient circumstance for inducing a regression in microvascular abnormalities.