Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Frontal and lateral views of the chest . A cardiac pacer with leads in the right atrium and right ventricle is noted . A ventriculoperitoneal shunt courses through the thorax . The cardiac silhouette has increased since ___ . The aortic knob is calficited . There are tiny bilateral pleural effusions . No pneumothorax .
    OUTPUT:
    
Interval enlargement of the cardiac silhouette since ___ could be due to differences in technique ; however , cardiomegaly or a pericardial effusion are possible .