Evaluation of Sildenafil for the Treatment of Moderate Congestive Heart Failure

Objective: To determine the effect of acute and long-term treatment with sildenafil on the clinical status of patients with moderate HF. Secondary Objectives: To determine the effect of acute and long-term treatment with sildenafil on cardiopulmonary exercise performance, the effect of acute and long-term treatment with sildenafil on neurohormonal activation, the effect of acute and long-term treatment with sildenafil on hemodynamics, and the effect of long-term treatment with sildenafil on quality of life. Background: Secondary pulmonary hypertension (PH) is a frequent manifestation of heart failure resulting in impaired vascular reactivity and permeability which contributes to the symptoms of HF. Levels of endothelin-1 (ET-1), a potent vasoconstrictor, are increased in patients with HF. At the same time, pulmonary artery nitric oxide (NO) production is decreased. NO increases concentrations of the second messenger cyclic-GMP, ultimately leading to vasodilation. This imbalance between NO-dependent vasodilation and ET-1 induced vasoconstriction likely contributes to the development of secondary pulmonary hypertension. cGMP is metabolized by the type 5 isoform of phosphodiesterase (PDE5) an enzyme that is highly expressed in the lung. Sildenafil, a selective PDE5 inhibitor, has been used extensively for the treatment of erectile dysfunction and has recently been approved for use in the treatment of PH. Recent studies of short-term administration of sildenafil in HF patients with secondary PH have demonstrated reductions in pulmonary arterial pressure, pulmonary vascular resistance, pulmonary capillary wedge pressure, and systemic vascular resistance while increasing cardiac index and exercise performance. However, it remains to be seen if sildenafil is safe and effective in the long-term treatment of heart failure. Methods: This will be an open-label, pilot study designed to evaluate the safety and efficacy of sildenafil for the treatment of moderate heart failure. The primary endpoint will be change in 6-minute walk test distance. Secondary endpoints will be changes in peak oxygen consumption (measured by cardiopulmonary exercise testing), neurohormones (b-type natriuretic peptide, catecholamines, ET-1), quality of life scores. Additionally, we will attempt to analyze responsiveness to sildenafil on the basis of PDE5 polymorphisms. Study procedures will be performed at the UNM General Clinical Research Center and the UNM Congestive Heart Failure Clinic. Patients will be hospitalized for 3 days to analyze safety and efficacy of sildenafil administered three times daily. Patients will complete exercise testing, neurohormone, and hemodynamic assessments at baseline (day 1) and following 24 hours of sildenafil treatment. The patients will then be discharged to complete a 12-week maintenance phase of treatment. At the conclusion of the maintenance phase the patients will be readmitted for 2 day to have repeat measurements performed. The main analysis will be done using paired t-tests. All statistical analysis will be performed using SAS v6.12.