The Effect of Tracleer® on Male Fertility

Inclusion Criteria: * Male patients age 18-65 years. * Bosentan-naïve. * PPH, WHO functional class III/IV, in need of TRACLEER * Patients pulmonary arterial hypertension (PAH) secondary to congenital heart disease. * Written informed consent. Exclusion Criteria: * Female * Patients with PAH secondary to connective tissue vascular diseases or HIV. * Patients who have undergone a vasectomy. * Patients with an average baseline sperm concentration \< 15 x 10\[6\]/mL, or any sample with a sperm concentration \<= 7.5 x 10\[6\]/mL. * Patients with an average baseline sperm motility \<20% or normal sperm morphology \<5%. * Body weight \< 50 kg. * Hypotension, defined as systolic blood pressure less than 85 mm Hg. * AST and/or ALT plasma levels greater than 3 times ULN. * Hypersensitivity to bosentan or any of the components of the formulation. * Treatment with glyburide, cyclosporine A or tacrolimus at inclusion or planned during the study. * Treatment with hormone suppressive agents, including androgens, estrogens, anabolic steroids or glucocorticoids within the past 6 months or planned during the study. * Current treatment less than 3 months prior to inclusion or planned treatment with prostacyclin or prostacyclin analogues (e.g., Flolanâ or Remodulin). * Patients who received an investigational drug in the month preceding the study start or who are due to be treated with another investigational drug during the study period. * Known drug or alcohol dependence or any other factors that will interfere with conduct of the study. * Any illness other than PPH that will reduce life expectancy to less than 6 months. * Active cancer. * Prior treatment with an anti-neoplastic agent or ionizing radiation. * Hot tub/Jacuzzi use. * Uncontrolled diseases including diabetes, liver or kidney disease. * Patients receiving spironolactone (aldactone) less than 3 months prior to inclusion or dose \>25 mg/day at baseline or anytime during the study.