Arterial Switch Procedure for D-Transposition of the Great Arteries

Pathophysiology

D-Transposition of the great vessels is a congenital cardiac anomaly in which the aorta arises from the right ventricle, and the pulmonary artery arises from the left ventricle. Desaturated venous blood returning from the peripheral tissue is pumped back to the systemic circulation while oxygen rich pulmonary venous blood is pumped back to the pulmonary artery. Patients present with cyanosis. Patients with transposition of the great vessels must have a communication between the systemic circulation and the pulmonary circulation to be consistent with life. Ideally, these patients will have a patent ductus arteriosus and an atrial septal defect. These work together to allow blood to shunt from the left atrium to the right atrium allowing oxygenated blood to enter the systemic circulation. Intravenous infusion of prostaglandin E1 will usually open the ductus arteriosus and a bedside balloon atrial septostomy is performed to create a communication between the atria.

The arterial switch procedure is usually performed in the first two weeks of life. Following the early newborn period, left ventricular strength will begin to regress as pulmonary vascular resistance falls. It is for this reason that the operation is performed in the newborn period while the left ventricle remains adequately prepared to support the systemic circulation.

Surgical Technique

The arterial switch procedure requires cardiopulmonary bypass and aortic cross clamping. Following aortic cross clamping, the ascending aorta and main pulmonary artery are transected. The left and right coronary artery ostia are visualized and excised from the aortic root with adjacent aortic wall as "buttons". The coronary artery buttons are then shifted posteriorly and implanted into the facing sinuses of the main pulmonary artery root. Next, the distal pulmonary artery and its branches are brought forward (LeCompte maneuver), and the distal aorta is moved posteriorly. The distal aorta is now anastomosed to the "new" aortic root. Reconstruction of the pulmonary artery is undertaken next, utilizing a patch of cryopreserved pulmonary artery homograft. Closure of the atrial septal defect completes the arterial switch repair. Transesophageal echocardiography is utilized to help assess adequacy of repair. Delayed sternal closure is sometimes required following surgery.

Postoperative Considerations

The postoperative course following arterial switch surgery can be variable. This is an extensive operation. Lengthy great vessel suture lines predispose these patients to postoperative bleeding. Myocardial dysfunction is sometimes encountered and may require moderate dose inotropic support. Patients who present late, following regression of neonatal pulmonary vascular resistance, are more likely to encounter left ventricular dysfunction. Invasive monitors utilized following surgery include arterial, central venous, and left atrial catheters. An oximetric catheter is utilized to monitor cardiac output. Vasoactive infusions required for hemodynamic management might include dopamine or dobutamine, epinephrine, milrinone, nitroprusside, phenoxybenzamine, and nitroglycerin. Cardiac arrhythmias are a rarely encountered postoperative complication. Intracardiac pressures following arterial switch surgery should be normal. Arterial oxygen saturation should be normal. Length of hospital stay following repair averages one to two weeks.