Introduction : Established pulmonary arterial hypertension (PAHI) carries bad prognosis.Early detection of underlying cause of PAH may be of great prognostic and therapeutic importance.Trans-thoracic and trans-esophageal echocardiographies are great tools for diagnosis of cardiac causes of PAH, but have their own limitations.Multi Detector Computed Tomography (MDCT), owing to it high spatial resolution can provide excellent information about cardiac chambers, shunts, pulmonary vessels and lung parencyma.Objectives: To determine incremental diagnostic value of cardiac MDCT over trans-thoracic and trans-esophageal echocardiography in determining secondary cause of PAH.