Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Heart is upper limits of normal in size and stable compared to previous study . Enlargement of the main pulmonary artery contour is unchanged since previous studies , and corresponds to a markedly enlarged pulmonary artery on prior CTA of ___ . Lungs are well expanded and clear except for unchanged nonspecific linear scarring in the left upper lobe . There are no pleural effusions or acute skeletal abnormalities .
    OUTPUT:
    
1 . No radiographic evidence of pneumonia . 2 . Unchanged nonspecific left upper lobe scarring , likely the sequela of a previous infection . 3 . Probable pulmonary arterial hypertension .