Safety and Efficacy Trial to Treat Diastolic Heart Failure Using Ambrisentan

Hypothesis: patients with pulmonary hypertension secondary to diastolic congestive heart failure (CHF) treated with ambrisentan for 16 weeks will have improved hemodynamics, increased exercise capacity and improved functional class with an acceptable safety profile, compared with placebo treated patients. Objectives: to evaluate the safety and efficacy of ambrisentan treatment in patients with pulmonary hypertension due to diastolic CHF. Efficacy will be assessed by improvement in hemodynamics (PVR(Pulmonary Vascular Resistance): primary efficacy endpoint), six minute walk distance (6MWD), World Health Organization (WHO) functional class and quality of life after 16 weeks of treatment with ambrisentan. Safety of ambrisentan will be compared to placebo. Concomitant Medication: Treatment with standard medications for CHF including diuretics and optimal blood pressure control with antihypertensive medications will be allowed throughout the study period. Diuretics adjustment will also be allowed and encouraged based on the planned diuretic management protocol. Approved medications for CHF in general are allowed as well, though it should be noted that there are no medications shown to have benefit in diastolic CHF. Patients may not be on an endothelin antagonist or sildenafil.