Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: AP upright portable chest radiograph was provided . Midline sternotomy wires are noted as well as mediastinal clips . A rounded density projects over the left mediastinal border which is of unclear etiology . Enlargement of the main pulmonary arterial silhouette suggests pulmonary arterial hypertension . The heart is mildly enlarged . The lungs appear grossly clear , though perihilar opacities could reflect bronchovascular crowding . No pneumothorax or effusion . Clips in the left upper quadrant noted . EKG leads and a catheter overlie the field of view somewhat limiting evaluation .
    OUTPUT:
    
Mild cardiomegaly with abnormal mediastinal contour . A chest CT is recommended with contrast to further evaluate .