Ventricular septal defect (VSD) is a form of congenital heart disease where there is a hole in the ventricular septum, between the ventricles of the heart. This hole allows blood to flow from the left side of the heart to the right, meaning a large volume of blood flows to the lungs. 

A large VSD causes high blood pressure in the pulmonary arteries (pulmonary hypertension) and means the left heart has to work harder than normal. This may lead to heart failure.

VSDs may close over time and not need treatment. Alternatively, surgery may be required. Pulmonary artery banding may be performed, allowing surgery to take place at a later date.

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