Palliative Operations for Tetralogy of Fallot

Dateline: 11/23/97

This week's article is about one of the most common severe birth defects of the heart, a condition called Tetralogy of Fallot. To learn more about the condition itself, you can read my article on it. This feature is about "Palliative Operations" for those patients who aren't candidates for a complete one-stage correction.

What are the palliative operations for ToF ?

The significant problem in ToF is REDUCED blood flow into the lungs. This results in reduced oxygen delivery to the body.
The operations designed to increase blood flow into the lungs are called Systemic-Pulmonary Shunts. These are connections between the aorta or one of its branches (the "systemic" arteries) and the pulmonary artery. The principle underlying these shunts is that a portion of blood flow from the arteries will be directed across the shunt into the pulmonary artery and its branches. This has two effects.

• First, by increasing the total lung blood flow, the amount of oxygen available for distribution to the rest of the body is increased.
• Second, the increasing amount of blood flowing into the pulmonary artery and its branches stimulates them to grow in size. The narrow portions may become wider. So, later, when an operation for total correction is performed, there is little or no obstruction to lung blood flow.

What are the types of systemic - pulmonary shunts ?

The BLALOCK - TAUSSIG SHUNT.

This shunt was the first of its kind, and revolutionised the treatment of "blue-baby" disease. Dr.Helen B.Taussig was a famous cardiologist, who studied heart disease in children in great detail. She thought of the idea of diverting blood from the subclavian artery, which is a branch of the aorta, to the pulmonary artery. (The subclavian artery is so named because it lies under - "sub" - the collar bone or clavicle - "clavian") . By improving the amount of lung blood flow, and increasing the oxygen content, it would relieve the cyanosis - or bluish discoloration.
In Dr.Alfred Blalock, she found a surgeon both highly skilled and daring enough to attempt this procedure on sick children. After practising many times on experimental animals, Dr.Blalock performed the first "shunt" operation on September 23rd, 1944 at Johns Hopkins Hospital, Maryland, USA.
The results were dramatic. At the end of the operation, when the clamps on the artery were released, the blue color of the child disappeared. Instead, the child turned a healthy pink - and the operating room personnel burst into spontaneous applause !
Ever since, the Blalock-Taussig shunt, or its "modified" version, have been used in the palliation of thousands of children with ToF, with great success.

How is this shunt created ?
Through an opening on one side of the chest, the surgeon has to first identify and free the pulmonary artery and the subclavian branch of the aorta. Clamps are applied on both vessels to allow better visualisation. The subclavian artery is divided, turned down and then sewed to an opening in the side of the pulmonary artery using fine hair-like thread made of polymers like polypropylene.
Although widely performed, this shunt has a few problems. The isolation and division of the subclavian artery is a time consuming and difficult procedure. Also, it carries a risk of injury to nerves that supply the hand and arm muscles, and to the blood supply of the upper limb.
In the modified version, which is most commonly performed now, the subclavian artery is not divided. Instead, an artificial tube made of material like PTFE (Poly tetra-fluoro ethylene) is used to create the shunt. The PTFE tube is sewn to the subclavian artery on one side and to the pulmonary artery on the other, using fine surgical sutures. In this way, the same effect is achieved, without interrupting either artery and with lesser risk.
The effects of a Blalock-Taussig shunt are immediate, and usually last long. The severity of cyanosis ("blueness") is reduced. However, it is only a temporary measure. It aims to improve oxygen supply and promote growth of the pulmonary artery branches. Once these have been achieved, an intra-cardiac repair can be performed safely.

How safe is a Blalock-Taussig shunt operation ?
A Blalock-Taussig shunt is a reasonably safe procedure. Complications are rare and include:

• Blockage of the shunt. This causes the blue color to return. Clot dissolving medication, or even repeat operation may be required.
• Infection. Since the PTFE tube is a "foreign" material, it may become a site of implantation for bacteria that cause infection.
• Excessive lung blood flow. This happens rarely when an inappropriately large PTFE tube is used. If left uncorrected, this may cause thickening and hardening of the lung blood vessels which compromise later corrective surgery.
• Distortion of the pulmonary artery. As a child grows, the point at which the PTFE graft is attached to the artery may not grow, causing a bend or kink in the pulmonary artery at that point.

What are the other types of "Shunt" operations ?

Instead of choosing the subclavian artery, other branches or even the aorta itself may be used in a shunt.
In the POTTS shunt, a direct connection is made between the lower part of the aorta (on the left side of the chest) and the left branch of the pulmonary artery. This operation was popular earlier, but has more or less been given up now. This is because of certain drawbacks, both in its function, and in the difficulty of closing it during the time of the total correction operation.
In the WATERSTON - COOLEY shunt, a connection is made between the back of the aorta and the right branch of the pulmonary artery. Though still popular in some hospitals, it is a difficult operation to perform perfectly.
In the DAVIDSON shunt, a short tube of PTFE is used to create a shunt between the aorta and the pulmonary artery through an opening in the middle of the chest.

If you enjoyed reading this article, please send me your comments. And you can subscribe to my FREE e-mail newsletter by filling in this brief form, or sending me a request e-mail.