Summarize the radiology report findings into an impression within 3 sentences.
    INPUT: Portable AP upright chest radiograph was obtained . The lungs are relatively well expanded and clear without pleural effusion or pneumothorax . The heart is mildly but stably enlarged , particularly the left atrial contour , with normal mediastinal and hilar contours .
    OUTPUT:
    
No acute intrathoracic process . Cardiomegaly and left atrial enlargement .