Sildenafil's protective effect against cardiac hypertrophy

Heart Failure with Preserved Ejection Fraction and Pulmonary Hypertension: Focus on Phosphodiesterase Inhibitors

Pulmonary hypertension (PH) is common in patients with heart failure with preserved ejection fraction (HFpEF). A chronic increase in mean left atrial pressure leads to passive remodeling in pulmonary veins and capillaries and modest PH (isolated postcapillary PH, Ipc-PH) and is not associated with significant right ventricular dysfunction. In approximately 20% of patients with HFpEF, "precapillary" alterations of pulmonary vasculature occur with the development of the combined pre- and post-capillary PH (Cpc-PH), pertaining to a poor prognosis. Current data indicate that pulmonary vasculopathy may be at least partially reversible and thus serves as a therapeutic target in HFpEF. Pulmonary vascular targeted therapies, including phosphodiesterase (PDE) inhibitors, may have a valuable role in the management of patients with PH-HFpEF. In studies of Cpc-PH and HFpEF, PDE type 5 inhibitors were effective in long-term follow-up, decreasing pulmonary artery pressure and improving RV contractility, whereas studies of Ipc-PH did not show any benefit. Randomized trials are essential to elucidate the actual value of PDE inhibition in selected patients with PH-HFpEF, especially in those with invasively confirmed Cpc-PH who are most likely to benefit from such treatment.

Phosphodiesterase 5 inhibitor sildenafil in patients with heart failure with preserved ejection fraction and combined pre- and postcapillary pulmonary hypertension: a randomized open-label pilot study

BACKGROUND

Heart failure with preserved ejection fraction (HFpEF) is frequently complicated by pulmonary hypertension (PH). A pulmonary vascular contribution could be considered as a substantial therapeutic target in HFpEF and PH and combined pre- and postcapillary PH (Cpc-PH).

METHODS

We enrolled 50 patients with HFpEF and Cpc-PH who were determined by echocardiography to have pulmonary artery systolic pressure (PASP) > 40 mmHg, pulmonary vascular resistance > 3 Wood units, and/or transpulmonary gradient > 15 mmHg.

RESULTS

The patients were assigned to the phosphodiesterase 5 (PDE5) inhibitor sildenafil group (25 mg TID for 3 months followed by 50 mg TID for 3 months; n = 30) or the control group (n = 20). In the sildenafil group after 6 months, the 6-min walk distance increased by 50 m (95% CI, 36 to 64 m); substantial improvement in NYHA functional class and exercise capacity during diastolic stress test were revealed; decreases in early mitral inflow to mitral annulus relaxation velocities ratio by 2.4 (95% CI, - 3.3 to - 1.4) and PASP by 17.0 mmHg (95% CI, 20.4 to 13.5) were observed; right ventricular systolic function (M-mode tricuspid annular plane systolic excursion) increased by 0.42 cm (95% CI, 0.32 to 0.52 cm; P < 0.01 for all). No changes occurred in the control group.

CONCLUSIONS

In a subset of patients with HFpEF and Cpc-PH assessed by echocardiography, PDE5 inhibition was associated with an improvement in exercise capacity, pulmonary haemodynamic parameters, and right ventricular function. The role of sildenafil needs to be considered in randomized trials in selected patients with HFpEF with invasively confirmed Cpc-PH.

TRIAL REGISTRATION

Russian National Information System of Research, Development and Technology Data of Civilian Usage (NIS, https://rosrid.ru), registration number 01201257849 . Registered 20 April 2012. This manuscript adheres to the CONSORT guidelines.

Differential regulation of PDE5 expression in left and right ventricles of feline hypertrophy models

Background

Though long known to affect smooth muscle biology, recent studies indicate that phosphodiesterase 5 (PDE5) is also expressed in myocardium. Recognizing that the regulation of PDE5 in hypertrophy is not well understood, we assessed the response of PDE5 expression and the level of cGMP-dependent kinase I (cGKI) in the left and right ventricles of feline hypertrophy models.

Methodology/Principal Findings

Using a cDNA library of feline aortic smooth muscle cells, we identified and cloned PDE5 cDNA for the first time in this species. The sequence shares 98% identity with its human orthologue at the amino acid level. E. coli expression of the cloned allele allowed selection of antibodies with appropriate specificity, facilitating the analysis of PDE5 expression in feline models created by selective proximal aortic (Ao) or pulmonary artery (PA) banding that resulted in hypertrophy of the left ventricle (LV) and right ventricle (RV), respectively. We demonstrated that PDE5 expression responded differentially with a decreased expression in the LV and an increased expression in the RV in the Ao-banded model. Similarly, in the PA-banded model, LV showed reduced expression while the RV expression was unaltered. In addition, the expression of cGKI was significantly decreased in the RV of Ao-banded group, correlating inversely with the increase in PDE5 expression.

Conclusions/Significance

The differential regulation of PDE5 and cGKI expression suggests that the mechanisms involved in hypertrophy could be different in RV vs. LV. Reciprocal PDE5 and cGKI expression in the RV of Ao-banded model suggests functional significance for PDE5 up-regulation.