Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Left pectoral single lead pacemaker in situ with the lead tip in the right ventricle . Left pneumothorax again noted measuring 18 mm in the apical area ( 40 mm previously ) . The heart size is stable . The right lung is clear . ECG leads on the chest . Tube projecting over the central chest .
    OUTPUT:
    
Interval reduction in size of the left - sided pneumothorax by approximately ___ % .