Pulmonary Vasodilation by Sildenafil in Acute Intermediate-High Risk Pulmonary Embolism – A Randomized Explorative Trial

Abstract

Background: To investigate if acute pulmonary vasodilation by sildenafil improves right ventricular function in patients with acute intermediate-high risk pulmonary embolism (PE).

Methods: Single center, explorative trial. Patients with PE were randomized to a single oral dose of sildenafil 50mg (n=10) or placebo (n=10) as add-on to conventional therapy. The time from hospital admission to study inclusion was 2.3 ± 0.7 days. Right ventricular function was evaluated immediately before and shortly after (0.5-1.5h) randomization by right heart catheterization (RHC), trans-thoracic echocardiography (TTE), and cardiac magnetic resonance (CMR). The primary efficacy endpoint was cardiac index measured by CMR.

Results: Patients had acute intermediate-high risk PE verified by computed tomography pulmonary angiography, systolic blood pressure of 135 ± 18 (mean ± SD) mmHg, increased right ventricular/left ventricular ratio 1.1 ± 0.09 and increased troponin T 167 ± 144 ng/L. Sildenafil treatment did not improve cardiac index compared to baseline (0.02 ± 0.36 l/min/m2, p=0.89) and neither did placebo (0.00 ± 0.34 l/min/m2, p=0.97).

Conclusion: A single oral dose of sildenafil 50 mg did not improve cardiac index but lowered systemic blood pressure in patients with acute intermediate-high risk PE. The time from PE to intervention, a small patient sample size and low pulmonary vascular resistance are limitations of this study that should be considered when interpreting the results.