Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: PA and lateral chest views were obtained with patient in upright position . Analysis is performed in direct comparison with the next preceding available PA and lateral chest examination ___ ___ . There is now status post sternotomy ( not present on the preceding examination six months ago ) . The heart size is at the upper limit of normal variation . Cardiac contour is somewhat obscured by extrapericardial apical fat pad on the left side and additional pleural and parenchymal thickenings suggestive of old scar formations . The lateral view discloses the presence of the metallic components of a porcine aortic valve prosthesis in place . There is a mild prominence of the left ventricular contour but no significant left atrial enlargement can be identified . There is no evidence of new acute pulmonary parenchymal infiltrates and the right and left - sided lateral as well as posterior pleural sinuses are free from any major fluid accumulation . Skeletal structures of the thorax grossly unremarkable . Similar as seen on the preceding chest examination , a nodular density projects on the frontal view in the left upper lobe area overlying the posterolateral contour of the left - sided sixth rib . This nodular density existed already on the preceding examination and has not undergone any change in size . Had been evaluated on previous chest CT of ___ , at which time they were considered to be stable and indicating benign etiology .
    OUTPUT:
    
In comparison with the next preceding preoperative chest examination ___ ___ , the patient has undergone sternotomy and aortic valve replacement . The heart size has not changed significantly , and no pulmonary congestion has developed . Prominent extrapericardial apical fat pad and linear scar formations on the left base existed already prior to operation and have not changed significantly . No evidence of acute pulmonary processes .