Phosphodiesterase-5 (PDE5) Inhibition and Pulmonary Hypertension in Diastolic Heart Failure

Heart failure (HF) with preserved left ventricular (LV) ejection fraction (EF) (HFpEF) is a public health problem and a major topic in clinical cardiology. Its prevalence, in fact, is increasing and the outcome seems to be similar to that of HF with LV systolic dysfunction (LVSD). Pulmonary hypertension (PH) in HFpEF is highly prevalent and often severe and, like in LVSD (3), is a predictor of morbidity and mortality (4). Because of the thin wall and the distensibility, the right ventricle (RV) is much more vulnerable by an excessive afterload than by preload. The pulmonary circulation is a central determinant of RV afterload, and an increase in impendance to RV ejection, like occurring in LV dysfunction, can easily result in RV failure, tricuspid regurgitation, central venous pressure (CVP) rise. Development of RV failure is unanimously viewed as a predictor of poor prognosis but the underlying mechanisms have not been extensively investigated.

Because of the prevalence and clinical significance of PH secondary to HF, attenuation of the pulmonary vascular tone and of the RV hemodynamic burden has been suggested as a goal to be achieved with HF therapy. Attempts with endothelin receptor antagonists, or prostacyclin analogues, were basically unsuccessful. Experimental models and human studies, showing that in HF nitric oxide (NO) - dependent pulmonary vasodilatation is impaired and pulmonary vascular resistance elevation is at least in part due to pulmonary endothelial dysfunction, have suggested therapeutic strategies with agents that increase NO activity, like nitrates or phosphodiesterase - 5 (PDE5) inhibitors (12-14). The latter agents offer the double advantage of selectively dilating the pulmonary vessels and not producing tachyphylaxis.

In this 1-year duration study, the primary end-point was to probe whether pulmonary hemodynamics and RV performance in HFpEF with PH may be targets of PDE5 inhibition with sildenafil.