The Arterial Switch Operation for Transposition of the Great Arteries Richard A. Jonas Transposition of the great arteries, together with tetral- Ijased on the fact that (luring fetal life hoth ventricles ogy of Fallot, is one of the most common congenital are exposed to the same pressure load. Thus, the left cardiac anomalies resulting in cyanosis. It is hardly ventricle is prepared at birth. However, hecause pulnio- surprising, therefore, that shortly after the introduc- nary resistance falls ra1)idlj within 6 to 8 weeks ancl tion of cardiopulmonary hypass in the early 195Os, perhaps as quicltly as within 2 to 4 weeks, the left attempts were made at anatomical correction of transpo- ventricle is no longer prepared. Iiitroduction of an sition, ie, the arterial switch procedure. These early essentially elective complex neonatal operation in 1983 attempts were uniformly unsuccessful for a number of initially met with consitlerahle resistance, particularly reasons : 1)ecause hy this time the surgical mortality for the atrial 1. Microvascular techniques were not adequately level procedures had reached very low levels. However, developed for delicate coronary artery transfer. a prospectivr study conducted Ijy the Congenital Heart 2. Pulmonary vascular disease is common in transpo- Surgeons Society‘ showed that the overall survival of an sition beyond the first year of life. entire population of patients with transposition en- 3. Surgeons failed to appreciate that in the presence rolled in the neonatal period was superior with the of an intact ventricular septum, the left ventricle was neonatal arterial switch approach because of the previ- inadequately prepared to acntely take over the pressure ously uncaptured deaths that occurred before atrial load of the systemic circulation. level procedures that were performed later in infancy. Various atrial level physiological procedures were Today, the primary arterial switch procedure in the developed in the late 1950s and early 1960s including neonatal period has become the standard of care the Senning and Mustard procedure. These procedures worldwide. were widely applied over the next 15 years, particularly after the introduction of balloon atrial septostomy by Rashlcind and Miller’ in 1966. This innovative proce- Indications for the Arterial Switch Procedure dure allowed for a 75% survival rate of transposition The main population of patients who should undergo patients with an intact ventricular septum. Previously, the arterial switch procedure are those with d-trans- these patients had either not survived or had to undergo position of the great arteries. In approxiinately 75% of a surgical septectomy procedure, usually the Blalock- these patients, the ventricular septum will be intact. A Hanlon procedure, which was introduced in 1950. small percentage of patients will have an associated In 1975, Jatene and associates’ described the first patent ductus arteriosus or secunduni atrial septal successful arterial switch procedure in a patient with defect (ASD). We continue to recommend that a halloon d-transposition of the great arteries and a large ventricu- atrial septostomy be performed if an adequate sized lar septal defect (VSD). By this time, thoracic surgeons ASD is not present. The atrial septal defect helps to had become familiar with microvascular techniques stabilize the patient during long distance transportation necessary for direct surgery on the coronary arteries. and is also useful intraoperatively in that it facilitates Also, there was appreciation of the need for the left intraoperative decompression of the left heart during ventricle to be adequately prepared. cardiopulmonary bypass with a single venous cannula In 1977. Yacoub and associate\’ descrihecl a method in the right atrium. Patients with transposition and to prepare the left ventricle in patients with transposi- associated VSD or multiple VSDs are also suitable tion and intact ventricular septum, thereby potentially candidates for the arterial switch procedure. Patients extending the arterial switch procedure to a much wider with a double-outlet right ventricle ancl a sub1mlinonai-y population of patients. However. this approach re- VSD are generally better suited to an arterial switch quired an initial palliative procedure followecl hy an procedure than an intraveiitricular repair. 4n arterial intermediate period of up to several months. In 1983, switch procedure can also he applied in the setting of the concept of primary neonatal arterial switch proce- L-loop transposition of the great arteries (congenitally dure was introduced by Norwood and Castaneda at mrrectetl transposition). In this setting, a concomitani Children’s Hospital, Boston, MA.4 This procedure was atrial level procedure must also I-)? perforinetl. Parti alar Challenges the arterial switch procedure has clocunientetl that coi-ofi(I ry 4ii utorny cwronar) artery anatomy is no longer a risk factor lor po.it.riorly placed coronary artery supplying left early mortality (Figure l).' ventricle. Early in our experience with the arterial Inverted riglit and circumflex coronary artery. switc'll ~~rocetlure,we fountl that cwronary artery pat- This coronary pattern is usually seen in association with terti< III which the left ventricle was I~l*e'l~tminatitly side by sick great arteries with the aorta lying to the suppl~t.tl1)y a coronary artery that passe(1 behind the right of antl perhap slightly anterior relative to the main maill 1 ,ulnionary artery from an origin either directly pulmonary artery. The right coronary artery antl from the right posterior facing sinus or as a hranch of anterior descending coronary artery arise from the right coronary artery (eg. Figure IA, hut not Figure the anterior facing sinus, whereas the circumflex coro- IB) c*at.rietl a higher risk of myocardial ischemia and nary artery arises from the posterior facing sinus. If death. It appeared that a fee.tlhack loop could be set up the circumflex coronary artery is particularly domi- in whir11 dilation of the left ventricle resulted in tension nant, the prohlem as described previously can exist. In on this cwronary artery that either lcinlcetl or flattened addition, because the anterior coronary artery must the coronary artery and resulted in worse left ventricu- he transferred in a direct leftward direction because lar ischemia. This then resulted in worse dilation and so of the side by side nature of the great arteries and on. It was found that awurate placement of the coro- because this is directly away from the line of the right nary I)utton, particularly with the aid of initial marking coronary artery there is a reasonable probability that sutures placed as the first step of the procedure, as well the anterior coronary insertion will be under some as careful avoidance of rotation of the aortic anastomo- degree of tension. Although mobilization of the right sis helped to reduce this risk. Furthermore, with time coronary artery from the atrioventricular (AV) groove we tended to mobilize more of the posteriorly placed can reduce this tension, it is occasionally necessary to coronary artery, perhaps as much as 5 or 6 mm, which extend the anterior coronary button. This can be allowed for some movement of the vessel in response to performed by adding a short tube, usually no more than the changing shape and size of the left ventricle. A 5 mm in length, constructed from autologous pericar- subsequent analysis of our more recent experience with dium. A A t t LTRP P Right Left anterior descending b/ Left circumflex coronary artery ' coronary artery w A Single right coronary artery B Single left coronary artery Fig I. Single right coronary artery (A) previously carried a higher risk of mortality probably hecauie of the long posterior course of the coronary artery supplying the left ventricle. Single left coronary artery (B) tloes not carry this risk. Single posterior coronary artery. This is exceecl- together it is possible to split the two coronary arteries ingly rare (Figure 11). There is a single ostium arising into two separate huttons and to transfer these in a posteriorly antl the right or left coronary artery passes relatively routine fashion. It may I)e nrcessar! to place between the aorta antl the pulmonary artery. This is a very fine sutures within the ostium of the coronary difficult situation to (leal with. Pro1)ahly the hrst option arteries themselves. It also is often necessary to detach is to rotate the hutton 90" posteriorly antl to cotnplete the llosterior ~~oiiiniiss~~reof the neopLilmonary valve. the anastomosis of the coronary hutton to the neoaorta This can su1)sequently be resusl)entletl on the pericar- with a hood of autologous peric*arcliuni. However, there dial patch, which is used to fill the coronary donor is significant risk that this area of coronary transfer will area$. he compressed between the neoaorta and the neopulmo- nary artery. Situations where a single coronary artery arises from either the right or left posterior facing sinus Left Ventricular Outflow Tract Obstruction and a coronary artery then runs behind the pulmonary Left ventricular outflow tract obstruction in association artery can be handled in the usual fashion including the with transposition can be either fixed or dynamic .' caveat as described previously. Fixed left ventricular outflow tract obstruction can be Intramural coronary arteries. We were initially due to hypoplasia of the pulmonary annulus, valvar concerned early in our arterial switch experience that pnlmonary stenosis, fihrous sulipdmonary stenosis, or the intramural coronary artery represented a high risk tunnel suhpulmonary stenosis. Alternatively, the oh- situation, but this has not eventuated. Generally, the struction may be dynamic, ie, the higher pressure in the left coronary artery passes intrainurally behind the right ventricle relative to the left ventricle results in the posterior rommissure of the original aortic valve and muscular ventricular septum bulging into the left ven- the ostium emerges in the right posterior facing sinus tricular outflow tract. Under these circumstances, per- relatively close to the ostium of the right coronary formance of an arterial switch procedure will result in artery.