Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: A small left apical pneumothorax persists and is non increased despite interval removal of the chest tube . No evidence of tension . No pleural effusion . Lung volumes remain low . Unchanged bibasilar atelectasis . Stable postoperative appearance of the cardiomediastinal silhouette with mild enlargement of the heart . Median sternotomy wires and the replaced mitral valve appear intact and unchanged in position .
    OUTPUT:
    
Stable small left apical pneumothorax after chest tube removal .