Repair of Tetralogy of Fallot

Transventricular repair of tetralogy of Fallot with pulmonary stenosis

Stage I: preparation

Through a median sternotomy, a partial thymectomy is performed and pericardium is harvested (it is pretreated with 0.6% glutaraldehyde for 10 minutes for subsequent use in the reconstruction of the right ventricular outflow tract).
The infant is placed on cardiopulmonary bypass using a single venous cannula placed through the right atrial appendage and an arterial cannula placed relatively high on the ascending aorta. The arterial duct is ligated if patent.
During cooling, the main pulmonary artery is completely mobilized from the ascending aorta, as are the right and left branch pulmonary arteries. At 18°C rectal temperature, the ascending aorta is clamped, cardioplegia is instilled, and the circulation is arrested. The right atrial cannula removed.

Stage II: Infundibulotomy and division of obstructing muscle bundles

A vertical incision is made into the free wall of the infundibulum.
If the pulmonary valve annulus is hypoplastic, the incision is extended to the bifurcation of the main pulmonary artery.
If the pulmonary valve leaflets are thickened or dysplastic, they are excised.
If there is narrowing at the orifice of the left or right pulmonary artery, the incision is extended into one of these vessels.
Proximally, the incision is carried to the level of the outlet septum. Deep hypothermia and cardioplegia render the heart quite flaccid, facilitating intracardiac exposure and therefore allowing for a shorter ventriculotomy. Because there is virtually no secondary hypertrophy of the infundibular structures and heavy muscular trabeculations are not present so early in life, resection of muscle mass from the outflow tract should be avoided.
A small tangential incision is made where the outlet septum fuses with the anterior (parietal) right ventricular wall (ventriculo-infundibular fold); this facilitates exposure of both the postero-inferior and postero-superior margins of the ventricular septal defect.

Stage III: Ventricular septal defect closure

The large malalignment type of ventricular septal defect is closed with a prosthetic patch using either a continuous suture technique or, preferably, interrupted horizontal mattress sutures (6-0 Teflon-coated Dacron) reinforced with Teflon pledgets (The use of Teflon pledgets permits a more superficial placement of sutures to decrease the risk of encircling and damaging the bundle of His, while at the same time avoiding suture line disruption)
It is convenient to place the first suture into the mid-portion of the outlet septum and to progress clockwise; each subsequent suture aids in exposing the margin of the defect.
When the level of the papillary muscle of the conus (Lancisi) is reached, the septal and anterior leaflets of the tricuspid valve are retracted inferiorly. Depending on the type of anatomy, sutures are placed within the postero-inferior muscular limb of the septal band, which is free of conduction tissue, or preferably, if the postero-inferior rim of the defect is fibrous, the stitches are anchored either within this tough tissue or within the muscular septum, distant from the edge of the ventricular septal defect. Fibrous tissue is a safe anchor for sutures, as conduction tissue, being specialized muscle, always courses within muscle.
Sometimes it is difficult to visualize the postero-inferior and postero-superior rim of the defect. Exposure of this area is facilitated by having the first assistant place a fine suction tip through the ventricular septal defect and retracting it toward the left.
Once all sutures are in place, an appropriately tailored prosthetic patch is used to close the defect.
In patients with a subpulmonary extension of the ventricular septal defect (i.e., absence of the outlet septum), sutures must be placed with much care within the fibrous band separating the pulmonary valve from the aortic valve.
The ventricular septum is searched for additional defects. The muscular portion anterior to the septal band is particularly suspect. If an anterior muscular ventricular septal defect is present, it is preferable to use a patch instead of primary closure to avoid tearing this often very friable tissue.

Stage IV:

If the pulmonary annulus is hypoplastic, a transannular patch is necessary. If the annulus is non-restrictive, the patch can be limited to the right ventricular outflow tract without crossing the annulus.
It is important to fashion the pericardial right ventricular outflow patch to be wide rather than tapered, both proximally and distally (rectangular shape), and to extend the patch into the left pulmonary artery whenever necessary to eliminate any obstruction at that level. Proximally, the length of the patch should be limited to about a third of the right ventricular length (measured from apex to pulmonary valve), and the width should approximate the normal size of the pulmonary valve annulus according to age. After anchoring the patch distally with one or two sutures, the atrial septum is examined. Small patent oval foramina are left open to allow right to left decompression in case of temporary postoperative right-sided failure and also to facilitate trans-septal left-sided catheterization studies later, after surgery. The right heart is then filled with saline, and the patient is placed back on cardiopulmonary bypass, again using a single cannula in the right atrium, the tip of which is positioned close to the junction of the superior vena cava and the right atrium. This technique allows for effective decompression of the right heart and limits the period of circulatory arrest to approximately 15 to 20 minutes. During rewarming, the patch on the right ventricular outflow tract is sutured with a continuous 5-0 Proline suture to the edges of the pulmonary artery and the right ventriculotomy incision. Before the pericardial patch is fixed entirely, a purse-string suture is placed within the epicardium in the right ventricular free wall and a 19-gauge catheter is guided into the left pulmonary artery to make it possible to monitor the infant postoperatively and also to obtain a pullback tracing, usually within 24 to 48 hours after the operation.

Stage V: Coronary reperfusion

Before removing the aortic cross-clamp, a generous hole is made in the proximal ascending aorta to allow air to escape. The lungs arc inflated vigorously to expel possible air trapped in the pulmonary veins. Cold saline can be infused into the left atrium to aid in removal of air from the left side of the circulation. The right coronary artery is temporarily occluded, and the aortic clamp is then removed. The heart usually defibrillates spontaneously or is defibrillated at an esophageal temperature between 27°C and 30°C.

Transventricular repair of tetralogy of Fallot with pulmonary atresia

The overall goal of repair of tetralogy of Fallot with pulmonary atresia is to achieve a biventricular repair with at least 15 of the 20 lung segments connected to the pulmonary trunk. The overall approach is a staged one, the first stage being to place a conduit between the right ventricle and the central pulmonary arteries. This allows the interventional cardiologists both to catheterize the patient and to assess which lung segments have a dual versus solitary blood supply. Aorto-pulmonary collateral vessels supplying segments of lung with a dual supply are coil-embolized, leaving that segment solely with a central pulmonary artery blood supply. Lung segments which are supplied by a solitary stenotic vessel are dilated or stented, as appropriate. Following optimization of the blood supply to each lung segment by interventional catheterization techniques, then unifocalization of aorto-pulmonary collaterals can be undertaken, the latter which may require two or more operations to perform. The last stage is to then close the ventricular septal defect once all of the peripheral pulmonary arteries have been unifocalized.

Therefore, the origin and the course of each aorto-pulmonary collateral must be clearly outlined preoperatively. In the majority of instances, they emerge from the posterior mediastinum, anterior to the left or right bronchus, to enter their respective hila. Before continuing with cardiopulmonary bypass, these vessels must be dissected and looped to prevent runoff from the systemic-to-pulmonary circulation, which would result in systemic hypoperfusion and left ventricular distention. In most instances, to approach these collaterals it is useful to dissect the area between the ascending aorta and the right superior vena cava through a midline sternotomy. Commonly, the more important aorto-pulmonary collaterals can be found in this area, coursing anteriorly to the right bronchus. In the few instances in which the aorto-pulmonary collaterals originate from the distal descending thoracic aorta or course behind the left or right bronchus, a preliminary thoracotomy is often necessary to either temporarily or permanently interrupt these vessels or to anastomose them to a pulmonary artery (unifocalization). Whenever an aorto-pulmonary collateral is an end artery and supplies a significant area of lung parenchyma (for example, one entire lobe), the collateral is detached from the aorta and anastomosed to the nearest branch of the pulmonary artery. As a general rule, as many bronchopulmonary segments as possible are incorporated; generally it is necessary to establish flow to the equivalent of one whole lung (10 segments) before considering closure of the ventricular septal defect. If the aorto-pulmonary collateral is the principal blood supply to one lung and this collateral cannot be approached from the midline, a preliminary shunt operation may be necessary to ensure sufficient pulmonary blood flow during detachment of the aorto-pulmonary collateral from the descending thoracic aorta. The vessel walls, particularly those of the pulmonary artery branches, are tenuous, and optimal surgical conditions are necessary to carry out an end-to-side anastomosis with 7-0 suture. It is our policy to confirm patency by obtaining an angiogram soon after unifocalization. Should additional unifocalization procedures be necessary on the opposite lung, this is accomplished, by preference, during the same hospitalization or soon thereafter.

If the aorto-pulmonary collaterals can be approached through a midline sternotomy, the collaterals are first dissected and are occluded immediately as the patient is started on cardiopulmonary bypass. This maneuver will hopefully diminish the threat of perioperative complications involving the central nervous system (e.g., acute or chronic choreoathetosis, which are observed in a few patients with uncontrolled aorto-pulmonary collaterals during cardiopulmonary bypass). Although the exact cause of this dreadful complication is not known, the possibility of a central nervous system "steal" phenomenon while the infant is on bypass, interfering with adequate blood supply to the globus pallidus and other related areas, seems a reasonable hypothesis. Because of this complication, every effort should be made to control as many aorto-pulmonary collaterals as possible before commencing the bypass. Once the infant is on bypass and during cooling, the aorto-pulmonary collaterals are either detached and anastomosed to the nearest pulmonary artery in an end-to-side fashion, as described previously, or ligated temporarily or permanently, depending on whether they are the sole blood supply or are part of a dual blood supply to an important segment of the lung. Also, because it is impossible to completely control all collateral flow on bypass, and to avoid ventricular distention, the left ventricle must be decompressed with a vent introduced through the junction of the right pulmonary vein and left atrium. At 20°C, tympanic temperature, flow is reduced to 50 ml/kg/min and Pco2 is maintained at 45 mm Hg or more. A tangential vascular clamp especially designed for infants is placed on the confluence of the right and left diminutive pulmonary arteries. A longitudinal incision is made, and the distal end of a 7- to 10-mm aortic or pulmonary artery homograft is anastomosed to the pulmonary artery using a continuous 7-0 polydioxanone suture technique. At this reduced flow and with the atrial cannula directed toward the junction of the superior vena cava with the atrium, it is rarely necessary to induce circulatory arrest. A vertical ventriculotomy is then made to allow for the anastomosis between the right ventricle and the proximal end of the homograft. Approximately 50% of the circumference of the homograft is anastomosed to the distal end of the right ventriculotomy, and the anastomosis is completed with a segment of glutaraldehyde-pretreated pericardium sutured to the remaining portion of the ventriculotomy and homograft. This pericardial baffle augments the anastomosis and prevents kinking or obstruction of the homograft. At this point, the patient is rewarmed; the ventricular septal defect is left open. With the improvements in transcatheter closure of midmuscular or apical ventricular septal defects, a perforated Dacron patch is sutured into the ventricular septal defect, facilitating later percutaneous catheter closure of the defect with a clamshell device.

Although small pulmonary arteries can be enlarged by systemic-to-pulmonary artery shunts, it should be cautioned that significant iatrogenic damage to these small branches of pulmonary arteries can occur after a classic or modified Blalock-Taussig shunt, and even more so following a Waterston shunt. Frequently these hypoplastic pulmonary arteries kink, reducing or completely obstructing ipsilateral or contralateral pulmonary blood flow. By establishing early right ventricular-to-pulmonary artery continuity with a conduit, leaving the ventricular septal defect open, the surgeon achieves antegrade and more even flow into both branch pulmonary arteries. Results after the use of cryopreserved, valved homografts are impressive. These offer significant advantages over prosthetic grafts with regard to technical ease of anastomosis to these very small pulmonary arteries and their long-term patency rate.

Discontinuous diminutive branch pulmonary arteries or absent mediastinal pulmonary arteries. In a few patients, diminutive branch pulmonary artery are present but are discontinuous; indeed, even fewer patients have no mediastinal pulmonary arteries. However, in the majority of these patients there is a pulmonary artery within the hilum, albeit small, that is suitable for anastomosis. In that case through a lateral thoracotomy, a 3.5- or 4-mm GoreTex graft us interposed between the right subclavian artery and the stump of the hilar pulmonary artery. Usually, during the same hospitalization, this procedure is repeated on the opposite side. The objective is to (1) stimulate growth of these diminutive pulmonary arteries, (2) eventually connect the left and right pulmonary arteries and 3) connect the reconstituted pulmonary arteries to the right ventricle using a valved homograft. Therefore, after angiographically documented enlargement of both left and right intraparenchymal pulmonary branches (usually after 6 to 12 months), through a midline sternotomy and on cardiopulmonary bypass, a 12-mm conduit (preferably a nonvalved aortic homograft) is interposed between the right and left hilar pulmonary arteries, and a valved aortic homograft is made to connect the right ventricle with the nonvalved aortic homograft.

In patients with absent mediastinal pulmonary arteries, the aortopulmonary collaterals are detached from the descending aorta through a right thoracotomy and are connected to the right subclavian artery or to the ascending aorta. using a 4- or 5-mm GoreTex graft, depending on age and size. During the same hospitalization, through a left thoracotomy, the left aorto-pulmonary collaterals are likewise detached from the descending thoracic aorta, adding unifocalization if necessary, and anastomosed to the left subclavian artery using a 4- or 5-mm GoreTex graft. To avoid development of pulmonary vascular obstructive disease, these children are brought back for cardiac catheterization in 6 months. This is followed by surgery, at which time the modified Blalock-Taussig shunts are detached from the ascending aorta and subclavian artery. The GoreTex shunts are removed, and, preferably, a valved homograft is placed between the right ventricular outflow tract and the left pulmonary artery directly. An additional extension of nonvalved aortic homograft is required to connect the valved homograft to the right pulmonary artery. The ventricular septal defect is closed only if both peripheral pulmonary arteries have enlarged sufficiently and the combined left and right blood supply exceeds that in 10 bronchopulmonary segments. Otherwise, the ventricular septal defect is left open and is closed at a third operation. It is occasionally advisable to transect the ascending aorta to facilitate anastomosis of the graft to the right pulmonary artery and also to place the graft in a retro-aortic position, which avoids retrosternal compression and allows for a shorter graft.

Transatrial repair of tetralogy of Fallot with pulmonary stenosis or atresia

The transatrial, transpulmonary approach to the repair of tetralogy of Fallot has been used for many years[456, 474, 1042, 1043]. The appeal of this approach is the advantage of minimizing or eliminating the need for a night ventriculotomy, with corresponding preservation of right ventricular function. The surgical technique includes closure of the ventricular septal defect through the right atrium and tricuspid valve and also relief of right ventricular outflow tract obstruction through the tricuspid and pulmonary valves. However, if enlargement of the pulmonary valve annulus is required, an incision is necessary across the valve ring, extending the incision only minimally into the right ventricular outflow tract. The operative mortality rate after transatrial repair of tetralogy of Fallot in older children has been low, and the reported early postoperative hemodynamic measurements are certainly encouraging.