Diagnosis of PH was based on Doppler echocardiography and defined as an estimated right ventricular systolic pressure (RVSP) of the > 40 mm Hg in the absence of left ventricular dysfunction (i.e., an ejection fraction under 50%), ischemic heart disease (manifested by regional wall motion abnormalities) or valvular heart disease. Right ventricular systolic pressure was estimated based on the modified Bernoulli equation (13) RVSP = transtricuspid gradient + right atrial pressure (RAP), where transtricuspid gradient is 4v2 (v = peak velocity of tricuspid regurgitation in meter per second) and RAP was estimated to be 5, 10 All the patients will undergo a D-dimer assay in the same day of the pulmonary function tests and Echo evaluations.