Tetralogy of Fallot

TOF is seen in patients with DiGeorge syndrome and may be present in combination with AVC defect in children with trisomy 21. Harsh systolic ejection murmur is detected in the first week of life. Hypercyanotic spells are life threatening and typically not seen in the first few months of life. This may be induced by dehydration. Surgical repair is planned at about 4–6 months of age. Severe restriction to pulmonary blood flow due to pulmonary stenosis or atresia may initially require a systemic to pulmonary arterial shunt. Free (severe) pulmonary regurgitation resulting from surgical enlargement of pulmonary valve annulus eventually causes right ventricular dilation and fibrosis which ultimately may result in ventricular arrhythmias. Severe pulmonary regurgitation after TOF repair should be corrected by surgery or interventional cardiac catheterization (currently experimental). Homograft valves (and other biological material) are used for this type of repair.


Introduction
Evidence suggests that early correction minimizes secondary damage to the heart or other organ systems due to chronic hypoxia, promotes pulmonary artery growth, and alleviates the stimulus for continuous right ventricular hypertrophy, thus preserving the mechanical and electrical stability of the heart. In the majority of centers, therefore, primary repair is electively performed before 6 months of age. The strategy of primary repair provides excellent outcomes, with mortality approaching zero, and acceptable morbidity. Avoidance of a shunt also has economical and psychosocial advantages. A combination of transatrial and transpulmonary approach is the preferred method. An effort is made to preserve the pulmonary valve, thus potentially limiting the negative impact of pulmonary regurgitation on right ventricular function. The need for a transannular patch is determined by the hypoplastic pulmonary artery annulus, and it is not eliminated by the shunt procedure. If a transannular approach is unavoidable, excision and patching should be minimal to prevent the long-term adverse sequelae associated with right ventriculotomy, particularly in the presence of pulmonary insufficiency. Depending on the institutional experience and policy, the staged approach remains a reasonable option.

Tetralogy of Fallot with Pulmonary Stenosis Anatomy
The anatomic feature of the tetralogy of Fallot is underdevelopment of the subpulmonary infundibulum, therefore the "tetralogy" is in fact a "monology." The abnormal superior, anterior, and leftward position of the infundibular septum results in crowding of the right ventricular outflow tract, a nonrestrictive malalignment-type ventricular septal defect, caused by non-occlusion of the infundibular septum with the left anterosuperior and right posteroinferior limbs of the septal band, varying degrees of overriding of the aorta, and ultimately, secondary hypertrophy of the right ventricle. The mechanism of the right ventricular outflow tract obstruction usually includes a combination of infundibular, valvar, and supravalvar obstruction. Isolated infundibular stenosis is created by a prominent parietal band, which has a well-developed infundibular chamber and pulmonary artery. The right ventricular-pulmonary trunk junction, surgically called the annulus, is small and obstructive when there is diffuse infundibular hypoplasia and/or fibrosis surrounding the subvalvar area. A stenotic pulmonary valve is present in 75% of cases. The valve is frequently bicuspid, with tethering of the leaflets; a commissural fusion is less common. The pulmonary trunk is frequently waisted at the commissural attachments of the pulmonary valve, creating supravalvar narrowing. If there is no additional source of pulmonary blood flow (apart from the ductus arteriosus), the capacity of the pulmonary artery bed should be adequate. However, anomalies such as stenosis at the origin of the pulmonary arteries, narrowing of left pulmonary artery with ductal shelf, or an absent left pulmonary artery with ductus dependent perfusion can occur. Typically, the ventricular septal defect is classified as type 2, (perimembranous) conal septal malalignment, tetralogy type. When the infundibular septum is absent, the ventricular septal defect is subarterial. Coronary artery anomalies are seen in approximately 5-7% of the cases. From a surgical point of view, the most important aspect is the origin of the entire left anterior descending coronary artery from the right coronary artery, which crosses the infundibulum at a variable distance from the annulus. The conduction system follows the same course as in other perimembranous ventricular septal defects. If there is a prominent posteroinferior limb of the septal band (trabecula septomarginalis), the conduction system is safely covered; other-wise, the bundle of His penetrates the right fibrous trigone and courses forward toward the muscle of Lancisi, along the inferior margin of the defect.

Indication for Surgery
Elective primary repair of tetralogy of Fallot with pulmonary stenosis in asymptomatic patients is delayed beyond 3 months of age. In symptomatic patients, primary repair is performed irrespective of age, weight, and preoperative status.
In the vast majority of patients, the size of the pulmonary arteries is adequate for correction. In newborns, the pulmonary arteries are undistended due to diminished pulmonary blood flow; therefore, a diameter of about 3 mm is sufficient. However, there is small subset of patients in whom the pulmonary arteries are indeed diminutive, precluding closure of the ventricular septal defect. The staged approach using a shunt is considered if the preoperative status precludes using the pump. The small size of the pulmonary arteries is not an indication for a shunt, because if the pulmonary arteries are suitable for a shunt, they should also be adequate for correction.

Approach and Cardiopulmonary Bypass Strategy
The heart is approached through a median sternotomy. The standard technique of cardiopulmonary bypass with mild hypothermia (32°C) is used. A left ventricular vent is inserted through the entrance of the right pulmonary veins.

Transatrial Approach with Release of the Right Ventricular Outflow Tract Obstruction The Goal of Surgery
Working through the tricuspid valve, effective release of the right ventricular outflow tract obstruction is accomplished by transection of the parietal band. Subsequently, the ventricular septal defect and atrial septal defects are closed.

Clip2
Dissection of the pulmonary arteries, closure of the ductus arteriosus. The aortic cross clamp was applied, and antegrade cold crystalloid cardioplegia was delivered. The pulmonary trunk was opened to inspect the pulmonary valve. The pulmonary valve was tricuspid, well developed and had no structural alterations.

Clip3
Release of the right ventricular outflow tract obstruction.

Clip4
Patch closure of the ventricular septal defect.

Clip5
Closure of the atrial septal defect and pulmonary artery trunk.

Transatrial Approach with Resection of the Right Ventricular Outflow Tract and Valvotomy of the Pulmonary Valve The Goal of Surgery
Working through the pulmonary trunk and tricuspid valve, effective release of the right ventricular outflow tract obstruction is accomplished by transection of the parietal band and by pulmonary valve surgery. Subsequently, the ventricular septal defect and atrial septal defects are closed. The pulmonary trunk should be enlarged with a pericardial patch.

Patient Characteristics
Age at operation: 2 months

Transatrial Approach with a Mini-Transannular Patch The Goal of Surgery
The need for transannular patch is determined by the severity of the right ventricular outflow tract obstruction. If the diameter of the pulmonary artery annulus is ≥ -3 Z, a mini-transannular patch is indicated. The short transannular ventriculotomy incision (5-10 mm in length) should avoid any conal branches of the right coronary artery. Only the parietal band is transected, preserving the moderator band. The ventricular septal defect is closed through the tricuspid valve. The geometry of the pericardial patch enlargement of the right ventricular outflow tract should be consistent with the size of the normal pulmonary annulus. If there is stenosis at the origin of the left pulmonary artery or if there is ductal shelf, a patch plasty is needed. The mini-transannular patch technique can result in significantly less right ventricular dilatation and better preservation of the right ventricular function in the long run.

Clip1
Echocardiogram and external anatomy of the heart.

Clip2
Opening of the right ventricular outflow tract and transection of the parietal band.

Clip3
Patch closure of the ventricular septal defect.

Clip4
Construction of the mini-transannular patch.

Tetralogy of Fallot with Pulmonary Atresia and Ductus-Dependent Pulmonary Circulation Anatomy
Tetralogy of Fallot with pulmonary atresia and ductus-dependent pulmonary circulation is the simplest form of pulmonary atresia with a ventricular septal defect. The pulmonary arteries are reasonably well developed. The right ventricular outflow tract either terminates at an imperforate pulmonary valve or narrows to a blind end point. The infundibulum either is developed, but is hypertrophied, thus obstructing the outflow, or the infundibulum is nearly completely absent. In this case, the ventricular septal defect is subarterial, and the aortic valve is anteriorly located, very close to the free wall of the right ventricle. In any case, there is no luminal continuity between the right ventricle and the diminutive pulmonary trunk or the pulmonary arteries. The ductus arteriosus is usually long and tortuous.

Indication for Surgery
Diagnosis is indication for surgery. Complete correction is preferable. If there is severe prematurity or any other preoperative risk factors contraindicating use of the pump, either stenting of the duct or shunt placement might be considered.

Transventricular Approach Preserving the Natural Connection of the Right Ventricle and Pulmonary Artery with Patch Enlargement of the Outflow Tract The Goal of Surgery
Resection of obstructing muscles in the outflow and opening of the atretic valve is required to create a natural connection between the right ventricle and the pulmonary artery trunk. The outflow is subsequently reconstructed with a pericardial patch, with or without monocusp valve. The closure of the ventricular septal defect is performed through the ventriculotomy. Echocardiogram and external anatomy of the heart.

Clip2
Opening of the right ventricular outflow tract and resection of the obstructing muscles -opening of the imperforated pulmonary artery valve.

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Transection of the obstructing muscles.

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Patch closure of the ventricular septal defect.

Clip5
Reconstruction of the right ventricular outflow tract.

Direct Connection of the Pulmonary Artery and Right Ventriculotomy with Patch Enlargement of the Outflow Tract The Goal of Surgery
The pulmonary artery is connected with the right ventriculotomy, either directly or by conduit. In newborns, it is nearly always possible to achieve direct, tension-free connection of the pulmonary artery with the right ventricle after thorough mobilization of the pulmonary arteries. Subsequently, the outflow is reconstructed with a pericardial patch. If a conduit is necessary, a pulmonary homograft or bovine jugular vein conduit is preferable. The closure of the ventricular septal defect is performed through the ventriculotomy.

Clip3
Transection and opening of the pulmonary trunk and the left pulmonary artery.

Clip4
Ventriculotomy and transection of the parietal band.

Clip5
Patch closure of the ventricular septal defect.

Clip6
Reconstruction of the right ventricular outflow tract.

Clip7
Final results of reconstruction.

Tetralogy of Fallot with Absent Pulmonary Valve Syndrome Anatomy
The absent pulmonary valve syndrome is very rare, accounting for 3-6% of all patients with tetralogy of Fallot. Apart from the intracardiac anatomy typical of tetralogy of Fallot, the pulmonary annulus is mildly to moderately hypoplastic, with vestigial nubbins of nonfunctional myxomatous tissue rather than developed valve cusps. However, the distinctive feature is the airway obstruction due to tracheobronchial compression that results from massive dilatation of the main pulmonary artery and its first-and second-order branches and from the abnormal branching of the segmental arteries. Consequential tracheomalacia and bronchomalacia determine the timing and severity of respiratory compromise, as well as the morbidity and mortality of these patients. A patent ductus arteriosus is never present.

Indication for Surgery
Early primary repair should always be considered. Symptomatic patients need to proceed directly to surgery, and asymptomatic patients should undergo repair early enough to minimize the potentially harmful effect of dilated pulmonary arteries on the tracheobronchial tree. These patients are operated on an elective basis, between 3 and 6 months of age.

Technique of Anterior Translocation of the Pulmonary Artery
The Goal of Surgery The first goal of surgery is the correction of the tetralogy of Fallot, using either the trans-atrial or the transventricular approach. The second, very specific goal is to decompress the airways from the dilated pulmonary arteries. The classical approach to decompression of the airways has focused on plication and reduction of the anterior or posterior wall of the normally positioned pulmonary arteries or on replacing the aneurysmatic pulmonary arteries by pulmonary homograft. Alternatively, one can translocate the pulmonary artery anterior to the aorta and away from the tracheobronchial tree. This technique has the potential to reduce or eliminate bronchial compression. One should keep in mind that only dilated right and left pulmonary arteries, up to the hilum, are amenable to surgery. Abnormalities of arborization, with tufts of arteries encircling and compressing the intrapulmonary bronchi, cannot be addressed during surgery. This could partially explain the high mortality rate of the youngest, symptomatic group of patients. Particularly in symptomatic patients, insertion of a valve homograft with anterior and/or posterior plication of the pulmonary arteries should also be considered, in order to decrease the wall tension and prevent later development of aneurysmal dilatation of the pulmonary arteries.

Patient Characteristics
Age at operation: 1 month

Clip2
The ascending aorta, aortic arch, and brachiocephalic vessels are widely mobilized. The superior vena cava is dissected free, and the azygos vein is transected to improve mobility of the superior vena cava.

Clip3
The standard technique of cardiopulmonary bypass with full flow and mild hypothermia (32°C) is employed. Myocardial protection is provided by crystalloid antegrade cardioplegia.

Clip4
Repair of the tetralogy of Fallot is undertaken first.

Clip5
A short, vertical incision is made in the infundibular portion of the right ventricle. Subsequently, the pulmonary artery trunk is transected above the annulus.

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After another dose of cardioplegia, the aorta is transected just above the commissures. At this point, one should consider shortening the aorta by resecting the appropriate tubular segment to facilitate an anteposition of the pulmonary artery.

Clip7
The pulmonary artery is brought anteriorly.

Clip8
The end-to-end anastomosis of the ascending aorta is performed.

Clip9
Direct connection between the obliquely shortened pulmonary trunk and the right ventricular outflow tract is accomplished.

Clip10
Complementary anterior-posterior downsizing of the pulmonary arteries is performed to decrease wall tension and prevent later development of aneurysmal dilatation of the pulmonary artery.

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