Arterial Switch Operation

Transcript of the video: Arterial switch operation is the ideal corrective surgery for D-Transposition or dextro transposition of great arteries, if it can be detected early in life. As the left ventricle is facing the pulmonary artery in dextro transposition of great arteries, if there is a delay beyond two to three weeks of life, there is possibility that the muscle mass of the left ventricle can regress, so that, later if arterial switch operation is done, it will not be able to face the systemic vascular resistance and it will fail. That is why, arterial switch operation has to be done very early in life. For the same reason, early detection by newborn screening is also important to facilitate arterial switch operation.

This is a very highly simplified representation of Jatene procedure, which is the other name for arterial switch operation. In dextro transposition of great arteries or D-TGA, there is ventriculoarterial discordance. That is, right ventricle is connecting to aorta, and left ventricle to pulmonary artery. In simple terms, arterial switch is restoring the normal connections. That is, pulmonary artery is transposed over to the right ventricle, and aorta over to the left ventricle, so that normal anatomy is restored. But that is easily said than done. It is much more difficult than you think from this simple block diagram.

This is a more realistic diagrammatic representation of arterial switch operation. This is the left ventricle, connected to the pulmonary artery before surgery, right ventricle connected to the aorta before surgery. You can see that the coronary arteries are arising from the aorta. And you can see that the left ventricular muscle is thick, because it is connected to the fetal pulmonary circulation with a higher resistance as the lung is not functional. This is the thickness which will come down, regression of left ventricular mass, if there is a delay in surgery. And this is the region where the transsections are done, and a button of the coronary artery (error) a coronary artery along with a button of the aorta, are also taken and transposed to the new aorta. This is the aorta here. This is transposition of the coronary arteries and you have a reconstruction of the pulmonary arteries as well. You can see that a small segment is added here. That is usually either a durameter piece, or a graft, synthetic graft can be added, as the pulmonary artery lengthe may not be enough to reach here. Some surgeons also do extensive mobilization of pulmonary artery, so that additional graft material can be avoided. Graft material has the disadvantage that it will not grow as the baby grows and can lead to supravalvar pulmonary stenosis later, one of the delayed complications of arterial switch. To prevent that, extensive mobilization of pulmonary artery and anastomosing directly has also used, in which case, delayed stenosis of the pulmonary artery has been lesser.

This is diagrammatic representation of stenosis of pulmonary artery at the site where it has been repaired. That can occur as a delayed complication of arterial switch operation, not in all cases, but in some cases. Then, when you have missed the initial window for surgery, corrective surgery, there is another method known as producing temporary obstruction to the pulmonary outflow, so that left ventricle does not regress. It can be either a natural stenosis if it is there, it will widen the time window for arterial switch operation. Suppose there is narrowing here, in the outflow, left ventricle is protected from regression. Another method is to produce a banding and then you can have a second stage repair so that left ventricle is thicker. Still another method adopted is intraoperative conditioning. First you band the pulmonary artery, partial obstruction is created for a period of a few hours, the surgery is delayed after that. Then there can be corrective surgery done. All these methods have been tried when the initial two to three weeks window for repair has been missed. And it is not possible at all, then what is done is atrial switching. That is instead of the arterial switching, what they do is that they redirect the atrial output to the ventricles in the opposite direction. Mustard and Senning procedures, they are known as atrial switch operations, alternative to arterial switch when time window for arterial switch has been missed.

This is diagrammatic representation of another of the complications, delayed sequelae of arterial switch. There could be enlargement of aorta, neoaorta, producing annuloaortic ectasia and aortic regurgitation, another long term sequelae of arterial switch operation. And still another is, when the coronary arteries are transposed, there could be stenosis at the site of coronary artery implantation. You should imagine that these are neonatal coronary arteries, which are quite small and it is easy to develop stenosis at the anastomotic region. In spite of all these potential complications, or delayed sequelae of arterial switch operation, arterial switch is still a much better long term option for treatment of transposition of great arteries, compared to the delayed procedure of atrial switch operation. Long term results are much better than atrial switch operations. Another problem with atrial switch operation is that, they are likely to have atrial arrhythmias, and several other problems and the physiology is not exact as in case of arterial switch operation.