Brief report: effect of ambrisentan treatment on exercise-induced pulmonary hypertension in systemic sclerosis: a prospective single-center, open-label pilot study.

Objective. Exercise-induced pulmonary hypertension (ePH) may represent an early, clinically relevant phase in the spectrum of pulmonary vascular disease. The purpose of this pilot study was to describe the changes in hemodynamics and exercise capacity in patients with systemic sclerosis (SSc) spectrumassociated ePH treated with open-label daily ambrisentan. Methods. Patients were treated with ambrisentan, 5 mg or 10 mg once daily, for 24 weeks. At baseline and 24 weeks, patients with SSc spectrum disorders exercised in a supine position, on a lower extremity cycle ergometer. All patients had normal hemodynamics at rest. We defined baseline ePH as a mean pulmonary artery pressure of > 30 mm Hg with maximum exercise and a transpulmonary gradient (TPG) of > 15 mm Hg. The primary end point was change in pulmonary vascular resistance (PVR) with exercise. Secondary end points included an improvement from baseline in 6-minute walking distance, health-related quality of life assessments, and cardiopulmonary hemodynamics. Results. Of the 12 enrolled patients, 11 completed the study. At 24 weeks there were improvements in mean exercise PVR (85.8 dynes x second/cm(5); P = 0.003) and mean distance covered during 6-minute walk (44.5 meters; P = 0.0007). Improvements were also observed in mean exercise cardiac output (1.4 liters/minute; P = 0.006), mean pulmonary artery pressure (-4.1 mm Hg; P = 0.02), and total pulmonary resistance (-93.0 dynes x seconds/cm(5); P = 0.0008). Three patients developed resting pulmonary arterial hypertension during the 24 weeks. Conclusion. Exercise hemodynamics and exercise capacity in patients with SSc spectrum-associated ePH improved over 24 weeks with exposure to ambrisentan. Placebo-controlled studies are needed to confirm whether this is a drug-related effect and to determine optimal therapeutic regimens for patients with ePH.