Repair of Interrupted Aortic Arch

Repair of interrupted aortic arch with ventricular septal defect

Palliative procedures for interrupted aortic arch are still used in many centers, and include pulmonary artery banding during the neonatal period with closure of the associated ventricular septal defect at some time beyond infancy but usually before 2 years of age. Arch continuity can be achieved by insertion of a synthetic conduit rather than by direct anastomosis. Both of these palliative options are generally undertaken by working through a left thoracotomy, although a combined thoracotomy and sternotomy for placement of an ascending-descending aortic conduit may also be used.

Single-stage complete repair in the neonatal period is the current preferred approach at many specialized centers. In addition to the usual monitoring equipment, careful consideration is given to the monitoring of the arterial pressure. It is preferable to be able to measure blood pressure both above and below the forthcoming anastomosis. Often this is achieved by placement of a right radial arterial line (unless an aberrant right subclavian artery is present) in addition to an umbilical arterial line. Not only does this allow for the immediate assessment of pressure gradients across the anastomosis, it also allows for the assessment of the adequacy of perfusion of the separate upper and lower body circulations via the dual arterial cannulation that is to be used during the cooling phase of the operation

Stage 1: Preparation

Medical & anesthetic considerations:

Aprotinin, solumedrol, Regitine, and antibiotics are given preoperatively. PGE1 is discontinued. The room temperature is lowered as much as possible to start surface cooling. Hyperventilation and a high FiO2 are avoided. Metabolic acidosis is treated aggressively with sodium bicarbonate. Inotropic agents, if any, should be continued until cardiopulmonary bypass has started.

A sternotomy is performed and the heart suspended in a pericardial cradle. The thymus, if present, is largely excised. It is generally unnecessary to harvest pericardium. The patient is heparinized, and a venous purse-string for single-venous cannulation is placed on the right atrial appendage.

Aortic purse-strings for double-arterial cannulation are placed. Accurate arterial cannulation is an essential key to the success of the procedure, as proper placement optimizes perfusion and cooling, and decreases the chance that either retrograde flow to the coronary arteries or antegrade flow to the brain will be compromised. Generally, a No. 8 French DLP arterial cannula is used for the ascending aorta, and a No. 10 French cannula for the pulmonary artery.

The pulmonary artery purse-string is placed on the very proximal pulmonary artery directly over the sinus of Valsalva. The aortic purse-string is placed on the right lateral aspect of the ascending aorta, just opposite the anticipated location of the anastomosis.

The right pulmonary artery is dissected free and snared down with a silk tourniquet. The proximal pulmonary artery and the right atrial appendage are cannulated, and the patient is placed on cardiopulmonary bypass and cooled to 18 - 20° C. The second arterial cannula is placed in the ascending aorta, and connected to the arterial infusion line with a U -connector.

The head is packed in ice, the ventilator is turned off, and the left pulmonary artery is dissected free and snared down with a silk tourniquet.

Stage II: Dissection

During cooling, the great vessels and head vessels are dissected free. The ascending aorta along with its branches are completely mobilized, and the arterial duct and the descending aorta are completely mobilized. This is especially important in order to minimize tension on the anastomosis.

If an aberrant right subclavian artery is present, it is usually ligated and divided at its origin with the descending aorta in order to improve its mobility. In a type B interruption, it is occasionally useful to divide the left subclavian artery in order to further facilitate distal aortic mobility.

In all cases, tourniquets are placed around each of the head vessels. A 2-0 silk suture is placed around the arterial duct.

Stage III: Protection of the Heart & Brain

A period of 20 minutes of core cooling to 18 - 20° C with the head packed in ice, and the room as cold as possible, is considered minimal protection for the brain. The tourniquets previously placed around the head vessels are tightened, and the pump is turned off and the patient drained through the venous line. Tourniquets around the pulmonary arteries are removed, cardioplegia is administered through the aortic purse-string. No aortic cross-clamp is needed as long as the head vessels are snared.

30 ml/kg of cold-blood, high-potassium cardioplegia is infused through the aortic cannula site and drained through the venous cannula. After the patient is fully drained to the circuit, the venous cannula is removed.

Stage IV: The Repair

The interrupted aortic arch is repaired:

The arterial duct is ligated and divided at its junction with the descending aorta. Any residual ductal tissue is excised from the descending aorta.

A spoon-shaped clamp is placed on the descending aorta past the arterial duct to draw up the descending aorta towards the ascending aorta.

The anastomosis is performed with 7-0 Maxon suture. It is situated on the ascending aorta where tension will be minimized, generally on the ascending aorta at the base of the left carotid artery. The anastomosis should be opposite the site of the ascending aortic cannulation.

The ventricular septal defect is closed. The approach to the ventricular septal defect should be decided upon preoperatively, and depends on the location of the ventricular septal defect and the prominence of the infundibular septum.

Under most circumstances, the infundibular septum is reasonably well developed, and the ventricular septal defect can be closed through a right atriotomy.

When there is extreme hypoplasia of the infundibular septum, the best approach is through a transverse incision in the proximal main pulmonary artery, immediately distal to the pulmonary valve. Under these circumstances, the main pulmonary artery is quite large. At the superior margin, sutures are passed through the pulmonary annulus, with the pledgets lying above the pulmonary valve leaflets in the sinus of Valsalva.

The atrial septal defect is closed. A decision should be made preoperatively regarding the need to close an atrial septal defect. If there is any doubt, the atrial septum should be examined through a short right atrial incision. Because of the poor left-sided compliance that often persists for some time postoperatively, even a small atrial septal defect can result in a large left-to-right shunt.

Stage V: Restoration Of Cardiopulmonary Bypass

The atrium and aortic root are filled with cold normal saline.

The arterial cannula in the ascending aorta is replaced and full-flow, full-rewarming cardiopulmonary bypass is restored.

The venous cannula is replaced.

The head vessel snares are removed.

Routine monitoring lines (i.e., a left atrial, pulmonary artery, and right atrial line) are placed during rewarming.

Interrupted aortic arch with ventricular septal defect and severe LVOTO

Very occasionally, obstruction of the left ventricular outflow tract may be sufficiently severe to justify a radical alternative procedure, such as that of the Damus-Kaye-Stansel operation originally described for transposition of the great arteries. Although some have believed it necessary to employ such a procedure relatively frequently, it is generally best employed on a selective basis only. Briefly, the Damus-Kaye-Stansel operation consists of directing left ventricular output through the ventricular septal defect by a baffle patch to the pulmonary artery. The main pulmonary artery is divided proximal to its bifurcation, and the proximal divided main pulmonary artery is anastomosed to the side of the ascending aorta. A conduit, preferably an aortic or pulmonary homograft, is placed between the right ventricle and the distal divided main pulmonary artery. Although this procedure is corrective in the sense that biventricular physiology is achieved, it is not truly corrective in that it does not incorporate growth potential. Variations on this theme have included an interim palliative procedure analogous to the Norwood procedure. When two ventricles are present, such an approach is difficult to justify, as it introduces all of the difficult postoperative management problems observed in the management of the hypoplastic left heart syndrome. Recent data from the Congenital Heart Surgeons Society suggest that these procedures are rarely, if ever, indicated.

Interrupted aortic arch with other anomalies

The general principle should be applied that if two ventricles are present, a biventricular repair incorporating growth potential should be undertaken whenever possible. For example, the child with transposition of the great arteries, ventricular septal defect, and interrupted arch should undergo an arterial switch procedure with ventricular septal defect closure and direct anastomosis of the arch. Although this complex procedure requires a long cross clamp time, it is generally well tolerated as long as an accurate repair is achieved. In fact, transfer of the aorta posteriorly, as part of the arterial switch, helps to reduce tension on the anastomosis of the arch. Similarly, in a child with truncus arteriosus and interrupted aortic arch, the large size of the truncus decreases the difficulty with which aortic cannulation is achieved when compared with such difficulty in a child with simple interrupted aortic arch, where the ascending aorta is often hypoplastic. Only single arterial cannulation is required for the cooling phase.

Management of the child with a single functional ventricle and interrupted aortic arch remains a significant challenge, presenting many of the same problems experienced with management of the hypoplastic left heart syndrome. Frequently, there is significant obstruction within the functional single ventricle, often in the form of an obstructive intraventricular foramen. This must be either bypassed, using a pulmonary-to-aortic anastomosis (Damus-Kaye-Stansel or Norwood procedure), or relieved by enlargement of the intraventricular foramen. Residual obstruction of the arch is poor]y tolerated with either a shunt-dependent circulation or pulmonary artery banding following enlargement of the intraventricular foramen. Such obstruction will result in excessive pulmonary flow unless such flow is severely restricted. This becomes a highly labile situation.