The Arterial Switch Operation

Surgical Repair of d-Transposition of the Great Vessels

Arterial switch operation for d-TGA with intact ventricular septum

Cardiopulmonary bypass can be conducted in a number of ways, depending on the surgeon’s preference or the time required to accomplish complete repair, particularly in the presence of a ventricular septal defect or other anomalies such as coarctation of the aorta or a hypoplastic or interrupted aortic arch. In a patient with D-transposition of the great arteries and an intact ventricular septum, the operation is preferably performed with the patient under either total circulatory arrest or continuous low-flow (50 ml/kg/min) hypothermic perfusion, limiting circulatory arrest time to the few minutes necessary to close the atrial septal defect. In the presence of a ventricular septal defect or other complex associated lesions, two periods of deep hypothermic circulatory arrest are used, interposing 10 to 15 minutes of hypothermic reperfusion is between them, or the arterial switch itself may be performed under continuous low-flow cardiopulmonary bypass, with profound hypothermic circulatory arrest for closure of the ventricular septal defect and other procedures such as repair of an interrupted aortic arch.

Stage I: Preparation

• Aprotinin, solumedrol (30 mg/kg), Regitine (0.1 mg/kg), and prophylactic antibiotics are given preoperatively.
• The sternum is opened, the patient heparinized, and a large segment of pericardium is harvested and prepared with 0.6% glutaraldehyde.
• The coronary arteries and great vessels are inspected.
• The arterial duct is dissected free, as are the left and right pulmonary arteries, including the first pulmonary artery branches in the hilum of each lung. The right pulmonary artery can be dissected prior to bypass, and the left dissected while on bypass.
• The ascending aorta is cannulated as far distally as possible to allow adequate length for the aortic anastomosis. A single venous cannula is placed within the right atrium. The left ventricle is vented with a catheter placed in the right superior pulmonary vein.

Stage II: Cardiopulmonary

• Cardiopulmonary bypass is begun, and the patient cooled for a minimum of 20 minutes to 20°C rectal temperature .
• The arterial duct is doubly ligated and divided, and the branch pulmonary arteries are completely mobilized.
• The site of aortic transection is marked before the cross clamp is applied. This is just distal to the pulmonary artery bifurcation, as best judged by the take-off of the left pulmonary artery.
• At 20°C rectal temperature, the distal ascending aorta is clamped, and cold blood cardioplegia is delivered into the proximal ascending aorta.
• The aorta is divided at the previously marked site, and the main pulmonary artery is divided just proximal to its bifurcation.
• The aortic and pulmonary valves are carefully inspected, as is the presence of left ventricular outflow tract obstruction.
• The Lecompte maneuver is performed, and the pulmonary artery is held in position anterior to the ascending aorta by moving the aortic cross clamp.
• The anterior commissure of the neoaorta is marked with a silk suture. Alternatively, the exact positions of the implantation sites are identified by juxtaposing the explanted coronary arteries or by placing marking sutures before cardiopulmonary bypass, when the aortic and pulmonary roots are distended.

Stage III: Coronary Transfer

• The ostium, the initial course of the left and right coronary arteries, and the presence of infundibular branches are identified.
• The coronary ostia are excised along with a large segment of surrounding aortic wall, extending the incision well into the base of the sinus of Valsalva.
• The proximal coronary arteries are mobilized sufficiently to avoid tension or distortion. Infundibular branches are very rarely sacrificed.
• The distal aorta is anastomosed to the proximal neoaorta with a continuous 6-0 Prolene or Maxon.
• The coronary implantation sites are prepared by making a neoaortotomy into the left and right anterior aspects of the neoaorta while the aortic cross-clamp is temporarily removed, angling the incisions from posterior to anterior, and using the commissural marking stitch as a guide.
• The coronary ostia are transferred by sewing the coronary flaps to these incisions with a continuous 7-0 Maxon suture.

• When the circumflex coronary artery arises from the right coronary artery, the site of right coronary implantation must be placed either higher than usual on the proximal neoaorta or, occasionally, above the suture line on the distal ascending aorta to avoid distortion of the circumflex artery.
• Adequate mobilization of the right coronary artery is frequently necessary to avoid distortion of the circumflex coronary artery. If the two coronary arteries originate from the same sinus, they can often be included in the same aortic flap (provided there is not an intramural course for one of the coronaries).
• If the coronary ostia are located closely adjacent (paracommissural) to the posterior commissure, excision of a segment of the posterior commissure of the native aortic valve (neopulmonary valve) is often necessary; the resultant neopulmonary regurgitation is generally mild and well tolerated.

Stage IV: Circulatory Arrest

• At this point, the pump is turned off and the venous cannula removed. The atrial communication is closed through a right atriotomy, which, as a rule, can be accomplished by suture closure after balloon septostomy, as there is usually no tissue deficiency.

Stage V: Right Ventricular Outflow Reconstruction

• The atriotomy is closed, and the aortic and venous cannula replaced.
• Cardiopulmonary bypass is resumed and the aortic cross-clamp removed.
• The left ventricular vent is turned on.
• Full-flow and rewarming are begun. An additional dose of Regitine 0.1 mg/kg is given in the pump.
• The coronary explantation sites in the neopulmonary artery are then filled, using a single, long, inverted bifurcated patch of 0.6% glutaraldehyde-pretreated, autologous pericardium. An incision is made into the pericardium to fit into the posterior commissure, and the free pericardial edge is sutured to the area of the aorta (neopulmonary artery) corresponding to the explanted coronary flaps, using a continuous 6-0 suture. When the anterior remnant of the aortic wall is reached, the pericardium, at this point cylindrically shaped, is tailored to bridge the distance between the proximal neopulmonary artery and the distal pulmonary artery without tension. Discrepancies in caliber between the proximal neopulmonary artery and the distal pulmonary artery are reconciled with this pericardial extension.
  • Alternatively, two separate pericardial patches can be used, one for the site of each coronary donor.
  • The relationship of the great vessels will require other certain modifications. With side-by-side great vessels, for example, a Lecompte maneuver is not always performed, and the central stoma in the transverse pulmonary artery is moved to the right pulmonary artery.
  • The proximal neopulmonary artery is anastomosed to the bifurcation of the native pulmonary artery. Some authors prefer to place the bifurcated pericardial patch as the first maneuver after removing the coronary arteries from the aorta and before coronary reimplantation in some cases.

Rapid Two-Stage Repair of d-TGA with intact ventricular septum

Through either a right thoracotomy or a midline sternotomy, a 3.5- or 4-mm polytetrafluoroethylene (GoreTex) graft is used to connect the right subclavian artery to the right pulmonary artery. Subsequently, and after minimal dissection, a Dacron-reinforced Silastic band is tightened around the main pulmonary artery to achieve a left ventricular pressure that is approximately 75% of systemic pressure. The pericardium is then loosely closed after thoroughly irrigating the pericardial space with heparinized saline to flush out any residual blood or fibrin clots.

The only modification required relative to the standard operative approach for the arterial switch operation is to first divide and oversew the modified Blalock-Taussig shunt, and to remove the pulmonary artery band. Because the second stage is carried out an average of 7 days after the first stage, adhesions do not usually present a problem. In the unusual situation in which the origin of the left coronary artery cannot be visualized after the banding, the arterial switch operation is deferred (for about 12 months) at which time clear delineation of the coronary anatomy can be made by coronary arteriography and/or magnetic resonance imaging.

The conventional treatment for neonates and infants with D-transposition of the great arteries, a ventricular septal defect, and hemodynamically significant left ventricular outflow tract obstruction has been an initial Blalock-Taussig shunt. However, either direct relief of the obstruction is attempted, accompanied by ventricular septal defect closure and an arterial switch operation, or, in the case of a long-segment hypoplastic left ventricular outflow tract obstruction or valvar pulmonary stenosis, a Rastelli operation using a cryo-preserved valved aortic or pulmonary homograft is performed (particularly in the neonate or young infant in whom the severe cyanosis is due in part to poor mixing, in spite of the possibility of adequate or even over circulation of the pulmonary vascular bed).

The occasional discrete subpulmonary membrane or excrescence of endocardial cushion tissue is easily resected through the posterior (pulmonary) semilunar valve. More common, and surgically more demanding, is left ventricular outflow tract obstruction caused by a posteriorly deviated outlet septum.

Once the ascending aorta and main pulmonary artery are divided in the course of an arterial switch operation, the obstructing muscle is more safely exposed through the pulmonary semilunar valve. Although exposure of the outlet septum is often easier through the anterior (aortic) semilunar valve, in patients with D-transposition of the great arteries, incision and excision of the outlet septum via the aortic valve run the risk of damaging the pulmonary valve, because the pulmonary semilunar valve originates at a lower level than the aortic semilunar valve. Therefore, the trans-pulmonary approach allows a more aggressive excision of the posteriorly deviated outlet septum, at the same time leaving sufficient muscle to anchor the ventricular septal patch. It helps to engage the outlet septum with a skin hook and to deliver it further into the left ventricular outflow tract before excising the muscle mass.

Often, in the case of a long, hypoplastic left ventricular outflow tract, resection is not feasible. In such cases a Rastelli operation is preferred to a palliative shunt operation, regardless of the patient’s age. After opening the chest through a midline sternotomy, an appropriate-size valved homograft (aortic or pulmonary) is selected, usually varying in size from 9 mm for a neonate to 14 mm for an older infant. In addition, a patch of pericardium is harvested and pretreated with 0.6% glutaraldehyde for later use to augment the anastomosis from the right ventricle to the homograft. Depending on the age and size of the child, either circulatory arrest or cardiopulmonary bypass with low-flow hypothermic perfusion is used. The main pulmonary artery commonly lies posterior and to the left of the ascending aorta, and its branches are dissected and the ligamentum arteriosum divided. If continuous cardiopulmonary bypass is used, the aorta is cross clamped at 25°C, and cold cardioplegia is injected. A vertical right ventriculotomy is then made to expose the aortic valve, the ventricular septal defect and the tricuspid valve. Unless the malaligned septal defect is larger than the diameter of the aortic valve, it is enlarged by making two incisions (at 2 o’clock and 4 o’clock) into the anterosuperior limb of the septal band. The intervening muscle is excised. This maneuver is important to achieve an unobstructed pathway between the left ventricle and the aorta. Interrupted horizontal mattress sutures, reinforced with Teflon pledgets, are placed first along the postero-anterior rim of the defect in a manner similar to the technique used for closure of a malaligned ventricular septal defect in tetralogy of Fallot. Additional interrupted stitches are then placed within the remaining circumference of the pathway from the left ventricle to the aortic valve. A baffle is then tailored from a tubular Dacron conduit (retaining approximately 50% of the circumference of the conduit), measuring the distance from the enlarged ventricular septal defect to the aortic valve rim. The sutures placed along the anterior border of the ventricular septal defect and the postero-anterior aspect of the ventricular defect are first threaded through the Dacron baffle and then tied in place. This partial fixation of the baffle offers the opportunity for adjustments in its length or width. The remainder of the sutures are then passed through the Dacron patch and tied. The Dacron baffle should contribute approximately 50% to the circumference of the pathway from the left ventricle to the ascending aorta, the remainder being composed of the patient’s own tissue. Next, either the aortic or the pulmonary valve homograft is prepared to cover the distance between the distal main and proximal left pulmonary artery and the right ventriculotomy. To avoid extrinsic compression of the homograft, the conduit is aligned along the left heart border; the left mediastinal pleura is opened to gain additional space for the conduit. After doubly ligating the main pulmonary artery proximally, the distal conduit-to-pulmonary artery anastomosis is fashioned with a 6-0 continuous suture. At this point the aortic cross clamp is removed. During rewarming, the anastomosis between the right ventricle and the homograft is begun at the most distal part of the ventriculotomy incision and is extended to include approximately 50% of the circumference of the proximal homograft stoma. At that point, the glutaraldehyde-preserved pericardial patch is sewn to the remaining part of the right ventriculotomy and to the free edge of the proximal homograft. This technique eliminates distortion of the anastomosis and ensures unobstructed flow through the homograft. After the air is vented and effective cardiac action has resumed, the infant is weaned from cardiopulmonary bypass. Catheters are routinely placed in the left and right atria and also in the trans-homograft pulmonary artery for postoperative monitoring.

The Arterial Switch Operation for Double Outlet Right Ventricle

An arterial switch operation is indicated for double outlet right ventricle which is at the d-transposition end of the spectrum - when there is little to no pulmonary or subpulmonary stenosis. It may be possible to resect muscular or fibrous tissue from the subpulmonary region as long as there is no important straddling mitral valve chordae. Similarly, a bicuspid pulmonary valve should not be considered an absolute contraindication to an arterial switch, particularly since both an atrial inversion procedure or a complex intraventricular repair with a conduit may result in a lesser quality of life

The general principles of the arterial switch operation for double outlet right ventricle are identical to those employed in the operation for d-transposition. The procedure is generally performed using low-flow hypothermic bypass for the extracardiac portion of the procedure while the intracardiac steps (i.e., closure of the atrial and ventricular septal defects) are conveniently performed during a period of circulatory arrest. Division of the great arteries is followed by inspection of the pulmonary valve and left ventricular outflow tract to ensure that there is no important outflow tract obstruction that might increase the risks from an arterial switch. Coronary mobilization and transfer are performed, followed by the aortic anastomosis. It is preferable not to undertake closure of the intracardiac communications before these steps are taken, as they will allow venting of left heart return to the single right atrial cannula. The single cannula is preferred to two caval cannulae for the same reason, as well as for the improved exposure provided by one cannula as compared with two.

The ventricular septal defect may be approached through the anterior semilunar valve, through the right atrium, or through a right ventriculotomy, as determined by the specific anatomic situation. Often there is some element of subaortic narrowing, so a right ventricular infundibular incision serves a dual purpose: access for closure of the ventricular septal defect and access for placement of an infundibular outflow patch to relieve outflow tract obstruction Approach through the semilunar valve or ventriculotomy often allows continuation of bypass throughout closure of the ventricular septal defect. The atrial septal defect is closed through a short, low right atriotomy, with the left heart filled with saline to exclude air before tying the suture.

With bypass re-established, the aortic cross clamp is released. Perfusion of all areas of the myocardium is checked. A single large pericardial patch is used to reconstruct the coronary donor areas, although to obtain optimal exposure, this step may be performed before the intracardiac steps. It is important that the pericardial patch actually supplement the neopulmonary artery (i.e., the patch needs to be quite a bit larger than the excised coronary buttons, because the aorta is frequently somewhat smaller than the pulmonary artery, particularly if there is a long and somewhat narrow subaortic conus). The pulmonary anastomosis is fashioned, and the patient is weaned from bypass. Specific variations of the arterial switch operation for double outlet right ventricle include:

Coronary patterns. Unusual coronary patterns are much more common with side-by-side great arteries than in standard transposition with anteroposterior great arteries. A common pattern is an anterior origin of the right and left anterior descending coronary arteries from a single ostium, with the circumflex originating from a posterior facing sinus. Extensive mobilization of the right coronary is necessary to prevent tethering of the anterior coronary, which must be transferred directly away from the line of the right coronary. Infundibular and right ventricular free wall branches of the right and anterior descending coronaries should be extensively mobilized from their epicardial beds to prevent tension on the arteries and on the anastomosis. On occasion, an autologous pericardial tube extension of the coronary artery can be used to avoid excessive tension. Excessive tension will be manifested by persistent bleeding from the coronary anastomosis and early or late coronary insufficiency. Another common coronary pattern with side-by-side great arteries is origin of the right and circumflex coronaries from the posterior sinus, with the left anterior descending artery originating from the anterior-facing sinus. It is important to guard against compression of the anteriorly transferred coronary by the posterior wall of the main pulmonary artery.

Closure of the ventricular septal defect. Exposure of the ventricular septal defect associated with double outlet right ventricle may present special difficulties. The defect may be quite leftward and anterior in what almost appears, from the surgeon’s perspective, to be a separate, leftward, blind-ending infundibular recess Exposure through the anterior semilunar valve and right atrium is particularly difficult, and even through a right ventriculotomy it may not be easily seen. Although exposure may be achieved through the original pulmonary valve, this is usually not recommended because of the risk of damage to the conduction system and the neoaortic valve. An additional complication to ventricular septal defect closure in this setting is the tendency for the very leftward ventricular septal defect to extend into the anterior trabeculated septum - that is, there appears to be no clear leftward and anterior margin to the defect. By taking large bites with pledgetted sutures, the size of any residual ventricular septal defect can be minimized. Catheter-delivered devices have been useful for ultimate closure of residual ventricular septal defects in this area.

Multiple ventricular septal defects. Surgical closure of multiple muscular ventricular septal defect as well as large subpulmonary ventricular septal defect may be difficult and may consume an excessive amount of circulatory arrest time. One approach to this problem is intraoperative delivery o a double-clamshell device. After division of the two great vessels, an excellent view is obtained of both sides of the ventricular septum. The sheath loaded with the device is introduced through the right atrium and tricuspid valve into the right ventricle A right-angled instrument is passed through the original pulmonary valve into the left ventricle through the ventricular septal defect, and into the right ventricle, where it grasps the delivery pod The pod is drawn into the left ventricle, and the lei ventricular arms are released under direct vision The pod is then carefully pulled back into the right ventricle, and, viewing through the original aortic valve into the right ventricular arms are released. If necessary, multiple devices may be placed. Although this system has worked well for children weighing more than 4 to 5 kg, the delivery pod requires further modification for neonates and infants weighing less than 4 kg.

Pulmonary artery anastomosis. Although the Lecompte maneuver is uniformly useful for patients with standard transposition in which the great arteries are positioned antero-posteriorly (or relatively close to this), for side-by-side great arteries judgment is required in deciding whether translocation of the right pulmonary artery anterior to the aorta will be useful in decreasing tension on the right pulmonary artery. In general, if the aorta is the slightest bit anterior to the pulmonary artery a Lecompte maneuver should be performed. Another consideration in this decision, other than just the tension on the right pulmonary artery, is the relationship of the transferred coronary arteries to the pulmonary artery. Care must be taken to ensure that there is no compression of the coronary arteries. A useful maneuver to minimize the risk of coronary compression, as well as to decrease the tension on the pulmonary artery anastomosis, is to shift the anastomosis somewhat from the original distal divided main pulmonary artery into the right pulmonary artery. The leftward end of the main pulmonary artery is closed (usually by direct suture, although the pericardial patch used to fill the coronary donor areas may be extended here), and the orifice is extended into the right pulmonary artery. In other respects the anastomosis is performed in the usual fashion. This maneuver has the effect of shifting the main pulmonary artery rightward so that it will not lie anterior to the aorta where it would likely cause compression of the anteriorly transferred coronary artery.

Repair of subaortic stenosis and arch anomalies. The long subaortic conus associated with double outlet right ventricle toward the D-transposition end of the spectrum may cause some degree of subaortic stenosis. Not surprisingly, aortic arch hypoplasia and coarctation often accompany such subaortic stenosis. There is likely to be considerable disparity between the diameters of the great vessels. During the preliminary phase of the arterial switch procedure tourniquets should be loosely applied around the head vessels. The coronary transfer should be undertaken in the usual fashion, using low-flow bypass. The circulation is then arrested, the tourniquets are tightened, and the aortic cross clamp is removed. An incision is made along the lesser curve of the ascending aorta and arch, extending across the coarctation. A long patch of pericardium is sutured into this aortotomy, which serves to minimize the disparity between the proximal neoaorta and the distal ascending aorta. The aortic cross clamp is reapplied, and bypass may be recommended. The remainder of the procedure is undertaken as described previously. Coarctation repair and pulmonary artery banding are not favored as preliminary maneuvers.