Abstract
It is believed that simultaneous targeting of two or more of the three pathogenic pathways of pulmonary arterial hypertension (the endothelin, nitric oxide, and prostacyclin pathways) is associated with additive or synergistic effects with subsequent increasing efficacy and improving outcomes. However, there is lack of evidence to guide the use of combination strategy among pulmonary arterial hypertension patients and many questions remain to be answered. One of these vital questions is whether the strategy of upfront initiation of combination therapy could improve patients outcomes compared to the strategy of initial monotherapy. The recently published AMBITION trial represents an important forward step towards answering this question by comparing a strategy of first-line combination therapy (ambrisentan and tadalafil) versus first-line monotherapy (ambrisentan or tadalafil) in patients with pulmonary arterial hypertension.