The study aims at studying the efficacy of tadalafil in patients with group 2 pulmonary hypertension with elevated pulmonary vascular resistance guided by RHC. After fulfilling the inclusion criteria, investigators will recruit 48 patients, and do baseline echocardiography for comprehensive right ventricular (RV) study and 6 minute walk test, and then start tadalafil 20 mg then 4mg if tolerated, for 24 patients (drug group). After three months follow up, investigators will follow up the patients regarding RV function and the functional capacity, compared to matched control group.
