What are atrial switch operations? Cardiology Basics

What are atrial switch operations? Cardiology Basics

Atrial switch operations were the initial operations developed for the treatment of transposition of great arteries. In transposition of great arteries, the aorta arises from the right ventricle and pulmonary artery from the left ventricle. Normally aorta originates from the left ventricle and pulmonary artery arises from the right ventricle.

In transposition of great arteries, systemic venous return is pumped back into the body without being sent to the lungs for oxygenation. Blood returning from the lungs is pumped back into the lungs.

So, survival is impossible unless there is good mixing by a congenital defect which permits mixing of pulmonary and systemic venous returns. Best form of mixing can occur if there is an atrial septal defect.

In those with poor mixing, an opening is created in the atrial septum in neonatal period by a procedure known as balloon atrial septostomy to improve systemic oxygen saturation and thereby survival. Balloon atrial septostomy catheter is introduced through the umbilical vein if it is done early after birth. Procedure can be done under fluoroscopy or echocardiography guidance and is an emergency palliative procedure. Corrective surgery is done later when the physical condition of the baby permits.

In the ideal surgery for transposition of great arteries, known as arterial switch operation, the abnormally positioned aorta and pulmonary artery are switched back to their expected positions. Arterial switch operation was described in 1975.

Prior to that transposition of great arteries was treated by switching the systemic and pulmonary venous return to the opposite side to functionally correct the transposition. These were called as atrial switch operations. The first one known as Senning operation, using atrial flaps, was described in 1957. The second one was Mustard operation, using pericardium, described in 1963.

While arterial switch redirects the arteries arising from the ventricles, atrial switch re-routes the blood coming to the atria.  In atrial switch, blood returning to the right atrium is redirected to the left ventricle. Similarly, blood returning from the lungs to the left atrium after oxygenation is redirected to the right ventricle. So, though the position of the arteries is not corrected, the type of blood which they receive are those which they should have received normally. Hence it is a functional correction of transposition of great arteries. Just as we say double negative becomes positive!