Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: There is a dual lead right pectoral pacemaker with leads noted within the right atrium and ventricle , respectively . Median sternotomy wires are well aligned . Mild cardiomegaly and mild central pulmonary vascular congestion are noted . Low lung volumes results in crowding of the bronchovascular structures . Left lower lobe atelectasis and a probable small pleural effusion are seen , with superimposed infection difficult to exclude . The upper lung fields are grossly clear .
    OUTPUT:
    
1 . Dense left lower lobe airspace opacity may represent effusion with atelectasis , although superimposed infection is difficult to exclude . 2 . Mild cardiomegaly , mild central pulmonary vascular congestion , and probable small left pleural effusion .