Abstract
Endothelial dysfunction of precapillary arterioles impairs nutritional microcirculation at rest as well as during post‐ischemic reactive hyperemia. In this monocentric, prospective, double‐blind, placebo‐controlled, randomized cross‐over study we investigated the acute effect of 50 mg sildenafil, a selective PDE‐5 inhibitor, on resting and post‐ischemic capillary circulation in twenty patients with angiographically confirmed coronary artery disease not taking nitrates or NO‐donors. Mean erythrocyte velocity in digital nail‐fold capillaries was determined before and after sildenafil and placebo, both baseline and after a three‐minutes supra‐systolic occlusion of the upper arm. Primary efficacy parameter was the drug effect on peak velocity during reactive hyperemia (peak velocity: Vmax ).
Post ischemic maximal capillary erythrocyte velocity Vmax significantly increased by 47% one hour after 50 mg sildenafil (mean value±standard deviation: 0.85±0.42 mm/s vs. 0.58±0.18 mm/s at baseline, p=0.0023), whereas placebo had no effect (p=0.5248). The difference between sildenafil and placebo was significant (p=0.0129) and sildenafil's effect can be regarded as biometrically highly relevant with standardized difference according to Cohen of 0.81.
In spite a small decrease of both systolic and diastolic blood pressure after sildenafil, sildenafil significantly increased capillary erythrocyte velocity at rest.
Conclusion: A single oral dose of sildenafil significantly increased resting and post‐ischemic cutaneous capillary circulation in patients with coronary artery disease. Future studies should assess whether sildenafil also improves nutritional capillary blood flow in other organs and in other diseases with impaired endothelial function and microcirculation, for example in diabetic microangiopathy.