Vasodilators have become the mainstay of therapy for PAH since 1996.13 Although published guidelines advocate their use in all PAH patients,14 these recommendations are counterintuitive for several reasons. Understandably, patients who qualify as responders are given calcium blockers in high doses with the expectation that the reduction in PAP achieved acutely will be reproduced over the long term. In contrast, patients who are nonresponders are recommended to receive a different class of vasodilator with the implication that these other vasodilators have some unique properties that will render them effective in minimally vasoreactive patients. Another conundrum is the extrapolation of vasodilator therapies to the entire classification of category 1 PAH patients, which implies a similarity of vascular pathology and pathobiology of each subgroup which is not the case. Thus, it has been recommended that these therapies are equally indicated for IPAH which may arise from inappropriate smooth muscle hypertrophy,15 scleroderma associated PH which may arise from autoimmune and inflammatory reactions in the pulmonary vasculature,16 and congenital heart disease associated with intracardiac shunting which may arise from high pulmonary blood flow and sheer stress in the endothelium.17 This may be one reason why the clinical results of vasodilator trials in the heterogeneous group classified as category 1 PAH are so mixed.18–21 Equally problematic is the lack of a validated assessment of how the right ventricle, which is always impaired in PAH, is affected by these drugs.22 Unfortunately, there has never been a single clinical trial designed to assess the effects of these therapies directly on the pulmonary arterial bed, or the right ventricular (RV) myocardium, as the randomized controlled trials have chosen the 6 MW test as the primary end point to support drug efficacy. Hemodynamics, when measured, were secondary outcome variables (Table 1). And although the target of vasodilator therapy in PAH is the pulmonary vascular bed, these vasodilators lack specificity for the pulmonary vessels, and have effects on the systemic circulation and myocardium which have largely been ignored in the clinical trials for PAH.