Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left chest wall dual lead pacing device is noted . Low lung volumes are seen with pulmonary vascular congestion . No visualized parenchymal markings identified at the left lung apex . Although no discrete pleural reflection is identified , this raises concern for underlying pneumothorax . Alternatively , could represent an underlying bleb . Moderate cardiac enlargement is accentuated by low lung volumes . Median sternotomy wires and mediastinal clips are noted . Posterior left seventh , through tenth rib fractures are noted .
    OUTPUT:
    
Lack of parenchymal markings at the left lung apex raising the possibility of underlying pneumothorax . Alternatively , bleb is possible . Posterior left rib fractures are noted , age indeterminate based on this image .