Sildenafil and phosphodiesterase-5 inhibitors for heart failure

Treatment of heart failure (HF) is a challenging task. An impaired nitric oxide pathway contributes to several abnormal cardiac and vascular phenotypes typical of the failing cardiovascular system. Inhibition of phosphodiesterase-5 (PDE5) is a new therapeutic strategy for overexpressing nitric oxide signaling by increasing the availability of cyclic guanosine monophosphate (cGMP). A number of background studies support the use of PDE5 inhibitors in HF. Treatment of pulmonary hypertension secondary to left ventricular dysfunction appears to be a primary target by virtue of the high PDE5 selectivity for the pulmonary circulation. Basic studies suggest that increased cGMP activity by PDE5 inhibition has potentially favorable direct myocardial effects that may block adrenergic, hypertrophic, and proapoptotic signaling. Furthermore, studies in humans have underscored the benefits of acute PDE5 inhibition on lung diffusion capacity, systemic endothelial function, muscle perfusion, and exercise performance. Despite promising initial data, larger controlled trials are necessary to define the safety, tolerability, and potential impact of PDE5 inhibitors on morbidity and mortality across the wide spectrum of patients with HF.