Arterial Switch Operation for Transposition of Great Arteries

Dateline: 12/07/97

This week's article is in response to a request from a visitor to detail the Arterial Switch procedure used in the treatment of the complex congenital heart defect called Transposition of the Great Arteries (TGA). If you have a topic you'd like to see featured here, please drop me a note.

What is the Arterial Switch procedure ?

The Arterial Switch Operation (ASO) is an elegant operation that is also simple in concept. Yet it was only first successfully performed in the late 1970s by Dr.Jatene in Brazil. This was mainly due to the technical difficulty in connecting the coronary arteries to the new aorta. Coronary arteries as you know are the first branches of the aorta, and supply blood to the heart muscle itself.

How is an arterial switch operation (ASO) done ?

Surgery is carried out through an opening in the middle of the chest. The heart will have to be stopped temporarily during the operation. So the surgeon will first hook up the patient to the heart-lung machine. The aorta and pulmonary artery are disconnected from their abnormal attachments. Their positions are then "SWITCHED". The aorta is stitched back to the left ventricle and the pulmonary artery to the right ventricle. A VSD is closed, if present. The coronary arteries are also freed, and connected back to the aorta using very delicate hair-thin sutures. When you consider that the size of these coronary arteries in a new-born is hardly a millimeter, you can imagine the technical skill and expertise that the surgeon must possess to carry out this connection without mishap.

What are the advantages of an arterial switch operation ?

• It restores normal structure to the heart. After the operation, the anatomy of the heart is just as in normal people. The heart is almost as good as new.
• The left ventricle is what pumps blood to the rest of the body. In the atrial switch operation, it is the right ventricle that does this job. Nature designed the right ventricle for less severe work - pumping blood to the lungs alone. When it is made responsible for the blood flow to the rest of the body, it may not be able to cope with the increased demands. Over many years, it may "fail". With the left ventricle, there is no such problem.
• Since there is very little suturing to be done inside the heart itself, the chances of later scarring causing rhythm disturbances - arrhythmias - are less with arterial switch operation.

What are the problems with an Arterial Switch Operation (ASO) ?

ASO is a technically demanding and difficult operation, and may take sometime to perfect. Different surgeons and institutions have varying results. ASO is not suited for all patients. Abnormalities in coronary arteries greatly increase the difficulty of an ASO. And an ASO cannot be performed in patients who come to medical attention at an older age, or who have severe pulmonary valve abnormalities.

What is the long term outcome after ASO ?

When an ASO is performed well, the mortality risk is minimal, and long term survival is excellent. Essentially all patients are active without any limitations. Although the longest follow-up is barely 20 years, it is predicted that about 90% of operated patients will survive to this period.
Late complications are uncommon. Rare problems are obstruction at the site of connection of the pulmonary artery to the right ventricle, producing Pulmonary Stenosis, and sometimes leak of the new aortic valve - Aortic Regurgitation. A second operation has hardly ever been necessary for these complications.

The other kind of operations for TGA are the Atrial Switch Procedures. Read more about them.