A breathing tube (endotracheal tube) will first be inserted into the mouth and down the windpipe (trachea) to maintain an airway. A urinary catheter is also inserted and connected to a collection bag to measure the patient’s urine output.

An incision is made in the chest and the breastbone (full median sternotomy). A retractor is then used to gently spread the edges and open up the chest. The child is connected to a heart-lung machine, which allows the heart to be safely stopped during the procedure. Once the heart has been stopped and emptied, the oxygen-poor blood flow is diverted to the pulmonary artery. This may be done by constructing a tunnel within the upper ventricle or by grafting a tube outside of the chamber. In some patients, a small window (fenestration) is used allow the blood to mix and to help balance the pressure. Some temporary drains will be placed in the child as well. 

After the procedure has been completed, the heart incision is closed and the heart is restarted. When the surgical team is satisfied that the heart is beating strongly again, the heart-lung machine is disconnected. The chest incision is then closed (sutured).