In this video, Dr. Radha Krishnan, Director, Pediatric Cardiologist at Fortis Escorts Heart Institute, New Delhi, will explain the criteria for differentiating mild, moderate and severe defects. It is generally a echocardiography findings and the measurements of the defects. Pulmonary artery pressure is predicted after the findings. If it is a large PDA or VSD, it will always cause pulmonary hypertension which damages the heart and lungs. After a certain period, pulmonary hypertension is irreversible. So it is always an emergency to close large PDA or VSD before six months of age.