Pediatric heart surgery Heart surgery home Congenital heart defects Atrial septal defect Ventricular septal defect    Tetralogy of Fallot Transposition of the great arteries Having Congenital heart surgery Before surgery Day of surgery After surgery

Tetralogy of Fallot (TOF) is the most common congenital heart defect causing cyanosis, a bluish discoloration of skin caused by oxygen-poor blood reaching the general circulation. An embryologic failure of the right ventricular outflow tract to form properly results in the four cardiac abnormalities characteristic of TOF:

• Ventricular septal defect (VSD): An abnormal opening between the two lower chambers of the heart

• Pulmonic stenosis (PS): A narrowed area within the main pulmonary artery, at, above or below the pulmonary valve

• Malpositioned aorta: The entrance to the aorta overrides the VSD

• Ventricular hypertrophy: An overly muscular right ventricle

In the normal heart, oxygen-poor blood returns to the right side of the heart where it is pumped to the lungs to be oxygenated. In TOF, the pulmonic stenosis increases the resistance to right ventricular outflow. This can cause elevation of right-sided heart pressures that may result in oxygen-poor blood being diverted across the VSD to the left ventricle and into the aorta (“right-to-left shunt”). When the aorta carries “mixed” blood to the general circulation, less oxygen is available to the tissues and cyanosis can result. Without surgical intervention, most patients with TOF will not survive past early adulthood.

What are the signs and symptoms of TOF?

Symptoms associated with TOF vary depending on the degree of obstruction to pulmonary blood flow. If the PS is minimal, blood will shunt from left-to-right across the VSD, and the patient may demonstrate signs of too much blood flow to the lungs: shortness of breath, heart enlargement and/or right heart failure.

If the PS is moderate, the patient may have a balanced circulation in which right heart pressures are elevated just enough to match the left heart, and relatively little shunting will occur across the VSD. These patients may demonstrate very mild or no symptoms. If the PS is significant, blood will shunt from right to left across the VSD, causing the patient to develop cyanosis. Many of these patients also will have Tet spells, which are sudden increases in the right-to-left shunting that result in severe cyanosis.

What are the surgical treatments?

The surgical approach to TOF repair is individualized for each patient based on age, anatomy and symptoms. Based on this assessment, surgery can be undertaken in one or two stages:

• First stage: Blalock-Taussig shunt: An artificial shunt is created between aorta and pulmonary artery to increase blood flow to lungs.

• First or second stage: Complete TOF repair. The VSD is patched to prevent right-to-left shunt, RV outflow tract widened to increase blood flow to lungs.

How is TOF surgery performed?

Two surgical options exist, depending upon the type of TOF. They are:

Blalock-Taussig (BT) shunt: Placement of a BT shunt is a closed-heart procedure in which the surgery takes place in vessels outside the heart. A heart-lung bypass is not needed. The chest usually is opened via a thoracotomy incision (between the ribs) on the patient’s right side. A connection is made between the subclavian artery and the right or left pulmonary artery. This may be accomplished by connecting the patient’s blood vessels or by placing a shunt made from synthetic material between the subclavian and the pulmonary artery branch. Placement of a shunt usually is a temporary measure designed to alleviate symptoms until the patient is able to undergo complete repair.

Complete TOF repair: This is an open-heart procedure. The chest is opened via a sternotomy incision through the breastbone, and the patient is connected to a heart-lung bypass machine. Depending on the location of the defect, an incision is made in the right atrium, the pulmonary artery or the outflow tract of the right ventricle. The right atrial approach in which the VSD is patched by working through the open valve (tricuspid valve) between the right atrium and the right ventricle is preferred. This approach prevents having to make an incision in the right ventricle that can lead to future right ventricular failure.

The patch for the VSD is created by the surgeon from either the patient’s pericardial tissue or a synthetic material such as Dacron, then sutured into place to close the defect. Any obstructive tissue in the right ventricular outflow tract is cut away. A second incision is made in the main pulmonary artery to complete the VSD closure and any additional resection of obstructive tissue. Additional work may be needed to widen a narrow pulmonary artery or valve, such as a patch. In some cases of severe obstruction or absence of the pulmonary artery, a conduit may be placed between the right ventricle and pulmonary arteries to provide an open communication for blood to flow to the lungs. After making these repairs, the atrial, pulmonary artery and/or infundibular incisions are closed with sutures, and the operation is completed.

See having heart surgery for general information about preparation, surgery and post-operative recovery for congenital heart surgery procedures.