Neurohormonal activation and pharmacological inhibition in pulmonary arterial hypertension and related right ventricular failure

During the last decade, hyperactivity of the sympathetic nervous and renin-angiotensin-aldosterone systems (SNS and RAAS, respectively) has repeatedly been related to the pathophysiology of pulmonary arterial hypertension (PAH) and PAH-related right ventricular failure (PAH-RVF), raising the question of whether neurohormonal inhibition may be indicated for these conditions. Experimental data indicate that the RAAS may be involved in pulmonary vascular remodeling, which is in fact halted by RAAS antagonism. Favorable actions of β-blockers on the pulmonary vasculature have also been described, even if information about β-adrenergic receptors in PAH is lacking. Furthermore, the available evidence suggests that stimulation of the pressure-overloaded RV by the SNS and RAAS is initially compensatory, but becomes maladaptive over time. Consistently, RV reverse remodeling has been shown in PAH animal models treated with either β-blockers or RAAS inhibitors, although important differences with human PAH may limit the translational value of these findings. Only few observational studies of neurohormonal antagonism in PAH and PAH-RVF have been published. Nonetheless, β-blockers on top of specific therapy appear to be safe and possibly also effective. The combination of mineralocorticoid receptor and endothelin-A receptor antagonists may result in an additive effect because of a positive pharmacodynamic interaction. While neurohormonal inhibitors cannot be recommended at present for treatment of PAH and PAH-RVF, they are worth being further investigated.