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

Patients with PE randomized to a single oral dose of sildenafil 50mg (n=10) or placebo (n=10) as add-on to conventional therapy. Right ventricular function 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.

Inclusion Criteria:

• Patients with acute pulmonary embolism confirmed by contrast enhanced computed tomography (CT)
• symptom duration of less than 14 days
• older than 18-80 years
• right ventricular/left ventricular ratio (RV/LV) >1 measured by trans-thoracic echocardiography (TTE, 1 cm above the atrio-ventricular valves in the four-chamber view at end-diastole).

Exclusion Criteria:

• pregnant
• cardiac arrest that required cardiopulmonary resuscitation
• a life expectancy <120 days
• systolic blood pressure <90 mmHg
• metal implants, obesity or claustrophobia that excluded the patient from cardiac magnetic resonance (CMR)
• altered mental status making the patient unable to provide informed consent
• recent use of drugs with influence on the Nitric oxide-cyclic guanosine monophosphate pathway
• known or suspected chronic thromboembolic pulmonary hypertension
• inability to perform study protocol < 72 hours after conventional PE treatment was instituted
• active bleeding after thrombolysis.

By request

Treatment was blinded by the institutional pharmacy embedding the placebo or treatment pill in a gelatinous cap