Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left - sided AICD / pacemaker device is noted with leads terminating in the right atrium and right ventricle . The cardiac silhouette is markedly enlarged . Mediastinal and hilar contours are stable . While there is mild prominence of the pulmonary vascularity , no pulmonary edema is seen . Retrocardiac opacity may reflect atelectasis , though an underlying effusion can not be excluded , nor can infection be excluded . No pneumothorax is demonstrated . There is no acute osseous abnormality .
    OUTPUT:
    
Marked cardiomegaly without pulmonary edema . Retrocardiac opacity may reflect atelectasis or infection , and a left pleural effusion can not be excluded .