Efficacy of Sildenafil in Severe Pulmonary Hypertension Secondary to Rheumatic Chronic Valvular Disease: A Double-Blinded Placebo Randomized Control Trial

Pulmonary hypertension (PH) secondary to left heart disease represents the most common form of pulmonary hypertension and is associated with significantly increased morbidity and mortality. In low- and middle-income countries, rheumatic chronic valvular heart disease remains a major contributor to left heart disease, with many patients presenting late with severe pulmonary hypertension and advanced right ventricular dysfunction. Severe pulmonary hypertension in this population complicates surgical decision-making, increases perioperative risk, and limits therapeutic options while patients await corrective valve surgery.

Sildenafil, a selective phosphodiesterase-5 inhibitor, increases cyclic guanosine monophosphate levels in the pulmonary vasculature, resulting in pulmonary vasodilation and improved right ventricular-pulmonary arterial coupling. While sildenafil has demonstrated efficacy in pulmonary arterial hypertension and selected forms of secondary pulmonary hypertension, evidence supporting its use in patients with pulmonary hypertension secondary to rheumatic valvular heart disease is limited. This randomized controlled trial is designed to evaluate the efficacy of sildenafil as an adjunct to standard medical therapy in patients with severe pulmonary hypertension due to rheumatic chronic valvular disease.

This study is a double-blind, placebo-controlled, randomized clinical trial conducted at the adult cardiology and cardiac surgery departments of the National Institute of Cardiovascular Disease (NICVD), Karachi and Hyderabad, Pakistan. Eligible patients aged 18 to 80 years with diagnosed rheumatic chronic valvular heart disease and severe pulmonary hypertension (defined as systolic pulmonary artery pressure ≥60 mmHg on echocardiography) will be enrolled. Participants will be randomized in a 1:1 ratio using permuted block randomization to receive either sildenafil 25 mg three times daily or matching placebo, in addition to standard guideline-directed medical therapy, for a duration of six weeks.

Randomization concealment will be ensured through an electronic allocation system, and outcome assessments will be performed by an independent team blinded to treatment allocation. Standard medical therapy will include rheumatic fever prophylaxis, diuretics, and guideline-directed therapy for heart failure where indicated. Patients undergoing corrective cardiac surgery within six weeks, those with contraindications to sildenafil, unstable cardiovascular conditions, or recent major cardiovascular events will be excluded.

The primary efficacy outcome is the change in six-minute walk distance from baseline to six weeks. Secondary outcomes include changes in right ventricular function and dimensions assessed by echocardiography, systolic pulmonary artery pressure, New York Heart Association functional class, and number of hospitalizations during the study period. Safety monitoring will include regular telephonic follow-up to assess medication adherence and adverse events, with predefined criteria for treatment discontinuation and trial termination in the event of significant harm.