Treatment With Ambrisentan in Patients With Borderline Pulmonary Arterial Hypertension

The treatment options and prognosis of patients with borderline pulmonary arterial hypertension (PAH) defined as mean pulmonary arterial pressure (mPAP) between 21-24 mm Hg measured by right heart catheterization (RHC) are understudied. The objective of this study is to determine the treatment effect of endothelin-receptor antagonist (Ambrisentan) for patients with borderline PAH when comparing with placebo. Accordingly, 420 patients with borderline PAH will be included in this prospective, randomized, double- blind, parallel group, placebo-controlled study. Repeat screening is required if last screening was performed \> 30 days ago. Baseline medical history will be obtained and physical examination will be conducted before signed consent and randomization. Moreover, an electrocardiogram (ECG), laboratory testing, and transthoracic echocardiography (TTE) at supine will be carried out before randomization and during follow-up. Subjects have to meet all inclusion criteria and have no anyone of exclusion criteria. This study will comprise 3 stages: 1) screening period (0-30 days), 2) 1-year study period (365 ± 30 days), 3) extended follow-up duration 3 years ± 30 days. Repeat measurements of cardiac function, hemodynamic, exercise capacity, and clinical events will be scheduled at the end of study.