The pathogenesis of PAH involves multiple mechanisms. However, three common factors are thought to cause the increased pulmonary vascular resistance that characterizes this devastating disease: vasoconstriction, pulmonary vascular proliferation and remodeling, and thrombosis in situ. Advances in our knowledge of the molecular mechanisms involved in PAH suggest that endothelial dysfunction with chronic impaired production of vasoactive mediators plays a key role. Reduced production of vasoactive mediators, such as nitric oxide (NO) and prostacyclin, along with prolonged overexpression of vasoconstrictors such as endothelin-1 (ET-1), not only affect vascular tone but also promote vascular remodeling. Thus, these substances represent logical pharmacological targets. Animal studies showed ET-1 could stimulate aldosterone secretion in different species, both in vivo and in vitro. This stimulation involves the ET-B alone and both ET-A and ET-B receptor subtypes in rats and humans. Animal studies also showed spironolactone combined with ACE inhibitor could normalize blood pressure, prevents upregulation of vascular ET-1, restore nitric oxide (NO)-mediated endothelial dysfunction. Beta-blockers have ability to reduce dp/dt in pulmonary artery, as well as left ventricle, thus prevent further damage to the dysfunctional endothelium. Furthermore, we observed from our practice that the aforementioned therapy could lower pulmonary artery pressure in patents with pulmonary hypertension secondary to left ventricular dysfunction. Thus, we hypothesize spironolactone combined with ACE inhibitor and beta-blocker has the ability to reverse remodeling of pulmonary artery in PAH patients.
