Data collection. Electronic database will have 178 variables including among others, data of onset symptoms, medical history, personal and family history, physical examination, six - minute walk distance, treatment, ECG, chest x-ray, echocardiogram, pulmonary function tests, V/Q lung scan, pulmonary angiography, right heart catheterization, acute vasodilator challenge, biomarkers and (in the follow - up) MACE.