Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Right - sided pacer device is noted with leads terminating in the right atrium and right ventricle , similar to the previous study . Mild enlargement of the cardiac silhouette is present with a left ventricular predominance . The aortic knob is calcified . Mediastinal and hilar contours are within normal limits . Patchy opacities are demonstrated in the lung bases . A trace left pleural effusion is present . No pneumothorax is identified . Pulmonary vasculature is not engorged . Remote chronic left - sided rib fractures are re - demonstrated .
    OUTPUT:
    
1 . Patchy opacities within the lung bases may reflect atelectasis , but infection is not excluded in the correct clinical setting . 2 . Trace left pleural effusion .