There have been several classification systems based on the variation in sources of pulmonary blood flow: exclusively from the native PAs as opposed to those with multifocal pulmonary blood supply (which can be a combination of MAPCAs and native PAs, or exclusively from MAPCAs) as shown in Fig. 35.2 :

• Type I : Intrapericardial PAs are present and fully developed (normal native PA system) with pulmonary blood supply coming exclusively from the patent ductus arteriosus (PDA). There are no MAPCAs.

• Type II : Absent main PA but normally developed intrapericardial confluent PAs, with blood supply exclusively from the PDA. No MAPCAs

• Type III : Multifocal pulmonary blood supply from MAPCAs. There are still confluent intrapericardial PAs (variable in size and distribution), and there is no PDA. *

• Type IV : Multifocal pulmonary blood supply with either absent intrapericardial native PAs or nonconfluent central PAs

Classification system for TOF with Pulmonary Atresia. Type I and II have native pulmonary artery system supplying the entire pulmonary vasculature, supplied by a PDA and no additional sources of pulmonary blood flow. Type III and IV have multifocal pulmonary blood supply: in Type III there is a combination of native PAs and MAPCAs and in Type IV there are MAPCAs only with absence of intrapericardial pulmonary arteries. TOF, tetralogy of Fallot; PDA, patent ductus arteriosus; PA, pulmonary artery; MAPCA, major aortopulmonary collateral artery.

(From Emani SM. Pulmonary atresia with ventricular septal defect and right ventricle-to-pulmonary artery conduits. 2147-2161 In: Sellke FW, Del Nido PJ, Swanson SJ, ed. Sabiston and Spencer Surgery of the Chest . St. Louis, Mo: Mosby; 2005.)

About 15% to 23% of MAPCA cases are of Type IV, where there is complete absence of intrapericardial native PAs. Among patients who do have intrapericardial vessels, up to 20% to 30% can be nonconfluent. It has also been recognized that even in patients with absent intrapericardial native PAs, the intrapulmonary distribution of the pulmonary vasculature may be more normal, originating from the hilum in some cases, whereas in others the distribution comes exclusively from MAPCAs where they enter the lung parenchyma.

The International Society for Nomenclature of Pediatric and Congenital Heart Disease (ISNPCHD) has adopted the classification proposed by Tchervenkov and Roy in 2000, which is used in the major databases around the world. The ISNPCHD classification divides TOF/PA into three major types according to the source and morphology of pulmonary blood flow, as shown in Fig. 35.3 :

• •

  Type A : Native PAs only supplied by the PDA (no MAPCAs)

• •

  Type B : Both native PAs and MAPCAs present

• •

  Type C : MAPCAs only (no native PAs)

Classification of PA, VSD (ISNPCHD), Type A- Native PAs, no MAPCAs; Pulmonary blood flow supplied by a PDA, Type B- Native PAs and MAPCAs Type C- MAPCAs only, no native PAs. PA, pulmonary artery; VSD, ventricular sepatal defect; ISNPCHD, International Society of Nomenclature for Pediatric and Congenital Heart Disease; MAPCA, major aortopulmonary collateral artery. (Drawings by Richard Tang, MD)

(From: Tchervenkov CI, Tang R, Peek GJ, Bleiweis MS, Jacobs JP. Pulmonary Atresia and Ventricular Septal Defect: Definitions, Nomenclature, and Classification. World Journal for Pediatric and Congenital Heart Surgery. 2025;16(2):173-176.)

These main types can be subdivided based on additional anatomic characteristics. For example, Type A of the ISNPCHD classification, can be further subdivided based on the presence or absence of a main PA: Type A1 , main PA present; Type A2 , main PA absent. Also Type B can be subdivided into two groups: Type B1 , MAPCAs, confluent native PAs, and no PDA, or Type B2 , MAPCAs, nonconfluent native PAs with the PDA supplying one lung via native PA and MAPCAs supplying the other lung. In the rest of this chapter, the ISNPCHD classification will be used.

There is great variation in the morphology of the pulmonary vasculature in TOF/PA, and the condition can be classified according to the nature and origin of the pulmonary vessels (see later). Even when the branch PAs are well developed, the pulmonary trunk is often hypoplastic ( Fig. 35.4 ) and may be a fibrous cord or even absent in 5% of cases.

Autopsy specimen of tetralogy of Fallot with congenital pulmonary atresia (same specimen as Fig. 35.1 ). Proximally, the pulmonary trunk ends blindly; distally, it extends directly into small left pulmonary artery. By contrast, right pulmonary artery arises almost at right angles from pulmonary trunk. Ao, Aorta; LPA, left pulmonary artery; PT, pulmonary trunk; RPA, right pulmonary artery; RV, opened right ventricular anterior wall; TSM, trabecula septomarginalis (septal band); TV, tricuspid valve.

Approximately 40% to 50% of patients with TOF/PA have native PAs alone (Type A), in which the native system supplies all 20 pulmonary arterial lung segments. The other 50% to 60% of cases will have a mixture of native PA and MAPCAs supplying the lung (Types B and C) and usually no PDA. There is considerable variability in how many lung segments are supplied by native PAs in these cases ^{, ,} ; usually the larger the native PA, the more segments it supplies. If there is nonconfluence of the central PAs, then 80% of cases will not supply all lung segments with the native PA system.

This morphologic variation in pulmonary blood supply is central to the concept of “sole supply” verses “dual supply” of lung segments in this population. In Type B and C, some segments may be supplied only by MAPCAs, whereas in others, there are intrapulmonary connections between the MAPCA and the native PA system, such that these areas are said to have dual supply. Thus, there is an inverse relationship between the numbers of segments supplied by MAPCAs and those supplied by the native system ( Fig. 35.5 ). Understanding the exact nature of blood supply to each area of the lung is the basis for the concept of unifocalization and in surgical planning.

Spectrum of lung perfusion in pulmonary atresia with ventricular septal defect. This is a hypothetical relation between number of pulmonary segments perfused by native pulmonary arteries (PAs) and those perfused by major aortopulmonary collateral arteries (MAPCAs) .

The intrapericardial PAs are usually of normal size in Type A (may have a localized stenosis associated with site of duct insertion ) but are variable and usually small in size in Type B or even absent in Type C. In a large study from Stanford, 23% of MAPCA cases had absent intrapericardial vessels, and in those that did have intrapericardial vessels, the mean size was only 2 mm.

If a ductus arteriosus is present and the branch PAs are confluent, arborization abnormalities and large MAPCAs are rarely if ever seen (Type I and II). The ductus is typically downwardly directed and serpiginous. If a ductus arteriosus is present and the branch PAs are discontinuous, the branch pulmonary artery (usually the left) that receives flow from the ductus rarely if ever has arborization abnormalities, and that lung rarely if ever has large AP collaterals. In this setting, the contralateral branch PA (usually the right) is almost always hypoplastic, has arborization abnormalities, or is completely absent, and the lung blood supply is solely from large MAPCAs.

In most cases of Type B and C the ductus is absent.

These are large embryonic (not acquired) muscular arteries that arise from the aorta or its branches to supply the pulmonary vasculature ( Fig. 35.6 ). Most commonly, they arise from the descending aorta, typically around the level of T4, and run anteriorly to reach the lung ( Fig. 35.7 ). They can arise from the head and neck vessels, the internal mammary arteries, the coronary arteries, and occasionally even from the abdominal aorta. Regardless of origin, MAPCAs typically take a serpiginous course to reach the lung, where they usually connect with an interlobar or intralobar pulmonary artery. ^, Their extrapulmonary segment is muscular and prone to develop stenoses (intimal pads) in as many as 60% of cases, often at points of bifurcation or at the connection to a native PA. ^{, ,} Stenoses may not be present at birth but can progress quickly, having been described at 3 to 4 months in vessels that were originally unobstructed ; some may even acquire complete occlusion. Stenoses are highly variable and unpredictable. Unobstructed MAPCAs can lead to overcirculation of the supplied area of the lung and pulmonary hypertensive changes if they are not intervened upon. ^{, ,}

Large aortopulmonary (AP) collateral arteries in tetralogy of Fallot with pulmonary atresia. (A) Two large AP collateral arteries come off right and anterior aspects of upper descending thoracic aorta and connect end to end with hilar arteries of right upper lobe. A smaller collateral artery supplies part of the lingula of left lower lobe. (B) Large AP collateral artery passes to the left and joins end to side to hilar portion of left pulmonary artery (LPA) in a manifold. The Y-shaped distal pulmonary trunk and central LPA and right pulmonary artery (RPA) fill from this manifold. Another large AP collateral passes to the right above RPA. (C) Branches of large AP collateral artery join end to end with hilar branches to left upper lobe, left lower lobe, and right lower lobe.

Arch aortography in tetralogy of Fallot (TF) with pulmonary atresia. Cineangiograms in (A) left anterior oblique (LAO) and (B) right anterior oblique projections show typical orientation of a left patent ductus arteriosus with left aortic arch. Ductus joins origin of left pulmonary artery (LPA). Contrast medium fills pulmonary trunk and right pulmonary artery (RPA) as well. LAO view shows normal (usual) brachiocephalic artery origins. Cineangiograms in lateral (C) and frontal (D) projections show typical orientation of patent ductus arteriosus when aortic arch is right sided. Here the right-sided ductus arises from distal arch to join the RPA. Contrast medium also fills the pulmonary trunk and LPA through narrowed proximal RPA. A, Ascending aorta; D, patent ductus arteriosus; DA, descending aorta; L, left pulmonary artery; PT, pulmonary trunk; R, right pulmonary artery; r, proximal right pulmonary artery.

The extrapulmonary course of MAPCAs is highly variable, and they can run posterior to the esophagus, posterior to the bronchi, or even pass through the wall of the esophagus. MAPCAs that remain posterior to the bronchi usually enter the lung posteriorly and can be difficult to access from midline-sternotomy. It is common for MAPCAs to originate around the T4 level of the descending aorta, where they usually run anteriorly beneath the carina to then find their way to the hilum of the lung. Retroesophageal MAPCAs are found in up to 60% of cases and always supply the lung on the opposite side to the aortic arch. They are commonly sole supply vessels to regions of the lung, and over 80% have some degree of stenosis. ^,

Once an MAPCA enters the lung, the arterial wall resembles that of a normal pulmonary artery. If the MAPCA joins the interlobular and intralobular artery as an end-to-end connection, this is said to be “sole supply” to that region. However, if the MAPCA creates an end-to-side connection with the native system (often joining near the hilum of the lung), this is referred to as “dual supply,” and the native system can be seen filling retrogradely on injection of the MAPCA at angiography.

Despite these characteristics of MAPCAs previously described, the distribution and branching pattern within the lung often include abnormal short and long stenotic regions or hypoplasia. ^,

Large systemic collateral arteries that arise from the midthoracic aorta and follow the course of the major bronchi and often are adherent to them are called bronchial collateral arteries. They are typically thin-walled and tortuous, and there is debate as to whether these are true MAPCAs or acquired dilation of bronchial arteries. However, if they supply important regions of the lung, then unifocalization and recruitment of these vessels is still recommended. These may reflect collateral arteries that develop much later in the embryonic course of the condition. Multiple small, acquired collaterals are common in cyanotic patients and increase over time, but these vessels are very different in size and number from MAPCAs, and there is no role for recruitment. They may regress once cyanosis has been corrected.

The aortic arch is right-sided in 25% to 30% of cases. Furthermore, the descending thoracic aorta may continue as a right-sided structure in more than half of these cases, descending on the right side of the vertebral column and usually returning to midline only at the level of the diaphragm. This is an important feature, as it will dictate the course of any MAPCAs arising from the descending aorta and inform surgical planning.

A third of cases with MAPCAs are associated with chromosome 22q11 deletion, of whom 90% will have DiGeorge Syndrome (Velo-Cardio-Facial Syndrome) and 22q11 deletion. The finding is more common in those with absent intrapericardial PAs and is also associated with pulmonary artery arborization abnormalities. ^, Other associated conditions include Alagille Syndrome and CHARGE association. The presence of genetic abnormalities/syndromes (especially 22q11 and Alagille) constitutes a significant risk factor for survival outcomes. ^, Other than in these syndromes, TOF/PA is not commonly associated with other noncardiac features.

PA, VSD with no MAPCAs will present like any duct-dependent lesion. Many are now diagnosed prenatally and so are placed on a Prostaglandin E2 infusion at birth. If the PAs are well developed and the PDA is large, then neonates may not appear obviously cyanosed but may develop signs of overcirculation. If not prenatally diagnosed, then neonates usually present as the duct closes with severe cyanosis and cardiovascular collapse.

PA, VSD with MAPCAs has a much more varied presentation, both in terms of symptoms and age at presentation. This reflects the great heterogeneity in the size and number of MAPCAs, presence or absence of natural stenoses in the vessels, and the overall quality of the pulmonary vasculature. Clinical phenotypes can be summarized as follows:

• •

  10% have large unobstructed MAPCAs. This can lead to overcirculation and high output cardiac failure with tachypnea, poor feeding, and weak pulses; typically present at 4 to 6 weeks and often with minimal cyanosis due to high pulmonary blood flow.

• •

  80% have a balanced circulation. MAPCAs either are relatively small or have natural stenoses limiting flow. These cases are not usually in heart failure and are mild-moderately cyanosed. However, there still may be some regions of the lung being overperfused and others at risk of losing their blood supply, so a clinically balanced situation still requires urgent imaging to assess pulmonary blood supply.

• •

  10% have small MAPCAs or severely stenosed MAPCAs, often with poorly developed pulmonary vasculature. These cases can be severely cyanosed and need ventilatory support. This can be the most challenging group to manage.

Primary and secondary airway problems may also contribute to the clinical presentation. The reasons are many, including upper airway extrinsic compression from a large aorta or pulsatile collateral arteries but can also be related to small airway hyperresponsiveness.

Most cases will present or be diagnosed as a neonate or in early infancy. Occasionally, well-balanced patients only present later in childhood when a murmur is detected or they are noted to be mild-moderately cyanosed.

Echocardiography is diagnostic for intracardiac anatomy and for defining the right ventricular outflow tract (RVOT). In Type A, it will delineate the ductal anatomy and the central PAs. In straightforward cases of Type A, no further imaging may be necessary. Echocardiography can usually demonstrate nonconfluent PAs, and doppler flow imaging may detect MAPCA origins, but other two-dimensional imaging is required to confirm presence of MAPCAs and define their anatomy, size, and distribution.

This is essential in all cases Type B and C of PA, VSD with MAPCAs, and also in cases of Type A where echocardiography alone cannot clearly delineate central PA anatomy. Angiography should define every MAPCA individually and demonstrate its size, origin, course, position, and the segments of the lung supplied. Follow-through imaging will demonstrate whether the MAPCA communicates with the native PA system (“dual supply”) or if it is the sole supply to that region of the lung. The native PA system often includes small, intrapericardial, native PAs that do not connect with the blind-ending RVOT and create a characteristic appearance described as a “seagull sign,” as these slender vessels move up and down with the movement of the heart ( Fig. 35.8 ). Pressure measurement in the proximal and distal vessels identifies areas of the lung at risk of pulmonary hypertension and also proximal stenoses within MAPCAs.

Angiogram showing diminutive central native pulmonary arteries fed from a MAPCA in the descending aorta. These small vessels move up and down with contraction of the heart (because the atretic main PA is in continuity with the blind-ending RVOT) and have the appearance of a “seagull” on cineangiogram. MAPCA, major aortopulmonary collateral artery; PA, pulmonary artery; RVOT, right ventricular outflow tract.

Angiography will also demonstrate ductal anatomy (if present) and should include imaging of the head-and-neck vessels, descending thoracic and abdominal aorta, as well as the coronary arteries to identify any MAPCA origins from these vessels. Anteroposterior and lateral imaging of each MAPCA is helpful to understand the extrapulmonary course of each MAPCA and relationship to the main airways.

If the pulmonary blood supply to some regions of the lung is not clear, then pulmonary venous wedge injections should be performed, as these may identify pulmonary vasculature fed by MAPCAs that have acquired origin atresia or even a native PA system fed by a ductus that has closed (so called “orphaned pulmonary artery” or “ghost pulmonary artery”).

Cardiac catheterization is usually performed in the neonatal period or early infancy to confirm the diagnosis of MAPCAs and to inform surgical planning. Stable patients may not need immediate intervention but repeat angiography of the MAPCAs may be necessary according to the planned surgery. The reason may be to reevaluate an infant at age 3 to 4 months immediately before a one-stage unifocalization and intracardiac repair, because collaterals can change dramatically in the first few months of life, or it may be to assess the results of a previous palliative procedure performed in the neonatal period. Clinical stability (i.e., a thriving infant with S _a O ₂ of 80% ± 5%) is not an indication to postpone cardiac catheterization. Such infants are likely to have important maldistribution of pulmonary blood flow despite their clinical stability, putting some lung segments at risk of developing pulmonary vascular disease due to overcirculation and other segments at risk of being lost due to collateral occlusion.

Computerized tomographic angiography (CTA) has become an essential adjunct to cardiac catheterization in defining the anatomy, course, and position of MAPCAs. The rapid advances in the quality and definition of CTA has made this extremely helpful in both precise anatomic diagnosis and in surgical planning ( Fig. 35.9 ). Three-dimensional reconstructions further aid surgical planning ( Figs. 35.10 to 35.11 ). Separate segmentation of the airways and esophagus help to define the relationship of individual MAPCAs with these structures. Advanced 3-dimensional imaging tools can create holographic images or virtual reconstructions where the clinician can use augmented reality and interactive software to understand the exact course of MAPCAs and their relationship to the airways, lung tissues, and the heart. These new technologies can also be employed in the operating room to further augment the surgeon’s ability to apply the imaging information to the surgical anatomy.

Computed tomographic angiography (CTA) of patients with pulmonary atresia with ventricular septal defect and large collateral arteries, illustrating the Stanford University management protocol. (A1 and A2) Two CTA images of a 1-week-old girl with very small centrally confluent native pulmonary arteries and large collaterals (MAPCAs). Images show a small right and left native right pulmonary arteries (RPA, LPA) and two major aortopulmonary collateral arteries (MAPCA2, MAPCA3) arising from the midthoracic descending aorta. Collaterals are connected peripherally to native pulmonary arteries. RML PA identifies right middle lobe branch of the RPA. LUL PA and LLL PA identify left upper and left lower branches of LPA. An additional very small collateral was present in this patient, but is not visualized in these images. According to the Stanford management protocol, this patient is identified as requiring neonatal surgery because of the normally arborizing and centrally confluent native pulmonary arteries, with all “dual-supply” collaterals. A neonatal preoperative cardiac catheterization with detailed angiography of the collaterals is required. (B) Coronal cut of a volume-rendered image of airways and aorta in a 1-week old girl with large collaterals to right lung. There is a right-sided aortic arch. Peripheral LPA is connected to aorta through a patent ductus arteriosus originating from left brachiocephalic artery. According to the Stanford management protocol, this patient would require neonatal surgery because of the presence of the unilateral ductus. A preoperative neonatal catheterization would be required to define the details of the right lung collateral distribution. Ao, Aortic arch; LLL , left lower lobe branch; LPA , left pulmonary artery; LUL , left upper lobe branch; MAPCA , major aortopulmonary collateral artery; PA , pulmonary artery; PDA , patent ductus arteriosus; RML , right middle lobe branch; RPA , right pulmonary artery.

Example of three-dimensional reconstructions from CT images in a case of Type B PA, VSD where pulmonary blood supply is from a combination of native PAs (in pink) and three MAPCAs (colored green, yellow, and blue). The corresponding angiographic image is also shown. The three-dimensional reconstructions can also include the airways so as to understand the relationships between the mediastinal structures. CT, computed tomographic; PA, pulmonary artery; VSD, ventricular septal defect; MAPCA, major aortopulmonary collateral artery.

Three-dimensional reconstructions from CT images showing postoperative appearance of the pulmonary vasculature from anterior and posterior view. The images can be color coded to show the contributions from the native pulmonary arteries (in blue) and the recruited MAPCAs (in purple). CT, computed tomographic; MAPCA, major aortopulmonary collateral artery.

This is less commonly needed than CTA, as anatomic definition of the MAPCAs is usually better with CTA. However, MRI can give valuable information on flow in individual larger collaterals and in shunts or in native vessels, calculate total collateral flow, and calculate Qp:Qs. Three-dimensional reconstructions may also help give similar spatial understanding to the course of MAPCAs in relation to other mediastinal structures.

The surgical management of d uct-dependent TOF with pulmonary atresia without MAPCAs is relatively straight forward: either complete repair, initial palliation with a systemic-to- pulmonary artery shunt or ductal stenting.

The management of patients with MAPCAs is much more complicated. Concepts of unifocalizatio n and r ehabilitation of pulmonary arterial vasculature are central to this process.

• Unifocalization implies bringing together all sources of pulmonary arterial supply surgically: both MAPCAs and native PAs if present.

• Rehabilitation has the goal of promoting growth of the hypoplastic native PAs so that it can be suitable for a two-ventricle repair. Rehabilitation can be anatomic to increase the size of the arteries by providing more systemic blood flow largely by means of an aortopulmonary shunt or sometimes stenting a PDA or severely stenotic collateral with hypoplastic distal bed. Rehabilitation can be physiologic where the PVR is higher and precludes a two-ventricle repair. These patients are treated with pulmonary vasodilators after unifocalizing to a restricted shunt. In some instances, large collaterals with high PVR can be banded and treated with pulmonary vasodilators. Physiologic rehabilitation is not common in the developed countries where patients are referred early for management. But it is common worldwide in many countries where patients are referred or diagnosed later in childhood and teenage years.

In some instances where the true PAs supply all or the majority of the lung with some collaterals, there appears to be a controversy whether to initially unifocalize or rehabilitate the PAs; both may be needed depending upon the adequacy. If there are MAPCAs supplying even a small portion (say two to four segments) of the lung, they should be unifocalized, incorporating all the lung segments to achieve the lowest RV pressures postrepair, along with pulmonary artery rehabilitation. However, if all the segments of the lung are supplied by hypoplastic true PAs, which are fed by MAPCAs, a rehabilitation only approach is preferred.

In “simple” PA/VSD, (i.e., Types A where there are confluent native PAs and duct-dependent circulation), initial management is to stabilize the neonate on a prostaglandin infusion and then plan neonatal intervention. The key decision is whether to offer primary neonatal repair or a staged approach in which an initial shunt or ductal stent is performed to secure pulmonary blood flow, with a plan for complete repair at 3 to 9 months of age.

The variability in clinical condition of these neonates will partly drive decision-making. Most cases are relatively stable and have balanced pulmonary blood flow with varying degrees of cyanosis. Regardless of the clinical condition, it is still essential to establish the diagnosis, including detailed imaging of all MAPCAs as early as possible.

There are three situations that may need neonatal intervention:

• 1.

  High Pulmonary Blood Flow: about 5% to 10% of cases have high pulmonary blood flow at birth and may have a degree of congestive heart failure, which can usually be medically managed at first with diuretics. Occasionally, respiratory distress can be exacerbated by airway compression from large MAPCAs. These patients will most likely need early surgery and will be suitable for early complete repair as they generally have well-developed pulmonary vasculature ( Fig. 35.13 ).

  

  Angiogram from a patient with Type C, TOF/PA in which there are several (four) large MAPCAs supplying the lungs. There is overcirculation that may cause congestive heart failure and the patient is suitable for early unifocalization and repair. TOF/PA, tetralogy of Fallot, pulmonary atresia; MAPCA, major aortopulmonary collateral arteries.

• 2.

  Low Pulmonary Blood Flow: a further 10% of cases have poor pulmonary vasculature and can be profoundly cyanosed at birth, with no response to prostaglandins. These can be some of the most challenging patients to manage and need early cardiac catheterization and CTA to define the pulmonary blood supply. These patients typically have several small MAPCAs that feed hypoplastic native PAs. Neonatal surgical intervention is indicated in these patients to try and drive flow into these underdeveloped vessels. Most commonly, this is in the form of creating a direct AP window between the ascending aorta and the hypoplastic PAs (known as a Melbourne or Mee Shunt ). If native central PAs are not present, then connecting surgical shunts to any accessible MAPCA target may be an alternative.

• 3.

  MAPCAs plus PDA: a third important consideration is the unusual group who have a PDA to one lung and MAPCAs to the contralateral lung (Type B2). These patients will respond to prostaglandin if the duct is closing. Even if these patients are clinically stable, they require a neonatal intervention to secure flow to the lung fed by the PDA (usually the left). This could be in the form of a PDA stent, a BTT shunt, or even neonatal complete repair if the MAPCAs are suitable.

This leaves the majority of cases, which are clinically relatively balanced and in whom neonatal intervention is not required. As outlined earlier, this does not mean that the patients are safe to leave untreated because many will have areas of the lung that are being overperfused (and at risk of pulmonary hypertensive injury) and other areas that are at risk of losing flow (due to worsening of proximal stenoses or even acquired atresia). Early and complete assessment of pulmonary blood flow should be completed, with cardiac catheterization and ideally CTA. Careful review of the angiography imaging (including three-dimensional reconstructions in some cases) will help create a roadmap of each MAPCA and their relationship to the airways and esophagus. It will also identify which MAPCAs are providing dual supply and which provide sole supply to each area of the lung.

Surgery is generally recommended at 3 to 9 months of age in these balanced patients, and the primary aim is to achieve complete unifocalization in one step. ^{, ,} This ensures that as much of the pulmonary vasculature as possible has been recruited and secured, eliminating any proximal stenoses (and the risk of developing proximal stenosis) of MAPCA origins. This also protects areas that were previously overperfused and allows the new confluence of vessels to be perfused uniformly at a constant low pressure. The decision for complete repair (i.e., VSD closure and RV-PA conduit) as part of the same procedure will depend on the adequacy of the pulmonary vascular recruitment and the PVR. As a general rule, if at least 75% of the pulmonary vasculature can be recruited (i.e., >15/20 lung segments), then it is likely that VSD closure can be safely performed.

Most centers recommend some sort of intraoperative pulmonary flow assessment to objectively measure PVR for final decision-making. Much of this approach is summarized in the Stanford Management Protocols, ^, as shown in ( Fig. 35.14 ) Calculation of the adequacy of the pulmonary vasculature is a combination of anatomic assessment through preoperative imaging and intraoperative flow studies. Standard use of a Nakata index is usually not helpful because of the multifocal source of pulmonary blood flow, although a modified approach, measuring the cross-sectional area of all vessels planned to be unfocalized may give an approximation of the vascular bed, aiming for a minimum of 200 mm ² /m ² for complete repair.

Stanford treatment algorithm for the management of newborns with Tetralogy of Fallot and major aortopulmonary collateral arteries.

(From Ma M, Mainwaring RD, Hanley FL. Comprehensive Management of Major Aortopulmonary Collaterals in the Repair of Tetralogy of Fallot. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu . 2018;21:75-82.)

The initial exposure, dissection and cardiopulmonary bypass (CBP) are similar to technique of operation as described for TOF with PS (see Chapter 34 ). In patients with Type A where there is a main PA segment, a transanular patch repair can be performed similar to the one described for TOF with hypoplastic pulmonary anulus (see “ Technique of Operation ” in Chapter 34 ).

For patients where there is no main PA, a conduit repair (valved or nonvalved) is needed, and some surgeons prefer this for all patients with TOF/PA (Type A). The choice of the conduit is variable. The authors prefer a homograft valved conduit. Other conduit options include bovine jugular vein with valve, handmade ePTFE, pericardial conduits incorporating ePTFE membrane valve leaflets, or synthetic conduits with bioprosthetic valves.

Exposure is through median sternotomy, and the thymus is resected to variable extent to provide unobstructed access to the heart and great vessels. A piece of native pericardium is harvested and preserved in glutaraldehyde solution for later use to close the VSD and sometimes an ASD. Alternatively, a Dacron or a Gore-Tex patch can be used for VSD closure. The PDA is dissected and controlled. As soon as CBP is established, the PDA is ligated and divided. The branch PAs are adequately mobilized. While the patient is being cooled, the distal conduit anastomosis can be performed to reduce the cross-clamp time. The homograft conduit is tailored. To do this, the surgeon should have a good idea of the extent of the ventriculotomy. The length of the conduit should not be excessive to avoid distortion of the branch PAs. When in doubt, a slightly shorter length is better, and this can be compensated for by mobilizing the branch PAs. The right and left PAs are opened adequately to match the distal opening of the conduit. The arteriotomy in the left PA is extended beyond the entry of the PDA to prevent any proximal LPA stenosis from constriction of the ductal tissue. The homograft conduit is then anastomosed distally to the PAs using a continuous 6/0 or 7/0 polypropylene suture. (Some surgeons prefer to do all of this after cardioplegic arrest.) After this, the aorta is cross-clamped and cardioplegia is administered to arrest the heart. A right ventriculotomy is needed for the proximal anastomosis of the conduit. Attention must be paid while extending the ventriculotomy incision superiorly toward the aortic root to avoid any potential damage to the aortic anulus or the leaflets. Muscle bands in the infundibulum are resected both to ensure an unobstructed subpulmonary region and to aid exposure of the VSD. The VSD is then closed through this ventriculotomy. (The technique of ventriculotomy and VSD closure is also described in “Technique of Operation” in Section I of Chapter 34 .) The autologous glutaraldehyde-fixed pericardium is tailored and used to close the VSD using continuous 6/0 polypropylene suture. An atriotomy is needed to reduce the size of the PFO or ASD. Some surgeons prefer to close the VSD through the transatrial approach. The proximal conduit is then anastomosed to the right ventriculotomy opening. This anastomosis is augmented using a hood of tissue (homograft or pericardium or synthetic patch) to avoid distortion to the pulmonary valve. The conduit is anastomosed to the RV starting posteriorly and picking up the VSD patch if possible to reinforce the anastomosis ( Fig. 35.15 ).

Right ventricular outflow tract conduit placement for tetralogy of Fallot (TF) with pulmonary atresia. Much of the surgical technique for repair of TF with pulmonary atresia is similar to that for TF with pulmonary stenosis (e.g., cardiopulmonary bypass [CPB], myocardial management, and intracardiac management of ventricular septal defect [VSD] and atrial septum). Management of these two malformations, however, deviates at several important points. Specific management of the pulmonary arteries depends on the form of pulmonary atresia. For duct-dependent atresia, ligation and division of ductus arteriosus is performed at commencement of CPB. For more complex forms of TF with pulmonary atresia and large aortopulmonary (AP) collateral arteries, complex reconstruction of the pulmonary vasculature is often required (see Figs. 35.17 , 35.18 , 35.19 , 35.20 ). Although in TF with pulmonary stenosis the VSD closure may be managed through a right atrial incision working through the tricuspid valve orifice, in TF with pulmonary atresia the VSD is always closed through an infundibular incision in the right ventricle (RV). In the various parts of this figure (and in Fig. 35.15 ), pulmonary artery anatomy is that of normally arborizing, normal diameter, confluent branch pulmonary arteries with patent ductus arteriosus. However, RV outflow tract conduit placement is the same for more complex TF with pulmonary atresia in which the pulmonary artery system has been reconstructed through unifocalization. (A) Ductus arteriosus has been ligated, taking care to avoid narrowing the left branch pulmonary artery. Dashed line on the distal pulmonary trunk shows site of transection in preparation for distal anastomosis of valved conduit to it. Opening in pulmonary trunk may need to be extended with incisions along left and right pulmonary arteries to accommodate circumference of the conduit. A longitudinal infundibular incision has been made and VSD closed with a patch and running suture technique. Note in this case that VSD has an inlet component. Hypertrophic muscle of the RV infundibulum and VSD closure are handled in a manner similar to that in TF with pulmonary stenosis. (B) Ductus arteriosus has been divided. A pulmonary allograft valved conduit is shown with the distal anastomosis performed end to end, allograft to pulmonary trunk. A running suture technique using fine monofilament suture is used. Proximal aspect of conduit is then attached to RV. Conduit is placed into ventriculotomy with the suture line attaching its proximal end to the infundibular septum within the ventricular incision. Although not shown in this figure, commonly the proximal suture line incorporates the upper aspect of VSD patch, which is also attached to the anteriorly displaced edge of the infundibular septum. (C) Posterior suture line of proximal conduit anastomosis is completed as it transitions onto free edge of infundibular incision. Proximal component of the reconstruction is completed using a roughly hemi-oval patch made of polyester, polytetrafluoroethylene, or glutaraldehyde-treated autologous pericardium. Straight edge of patch is sewn around remaining anterior aspect of proximal conduit, and curved edge is sewn around ventriculotomy site to complete the reconstruction. All sutures lines are running nonabsorbable monofilament suture.

(From Ma M, Mainwaring RD, Hanley FL. Comprehensive Management of Major Aortopulmonary Collaterals in the Repair of Tetralogy of Fallot. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu . 2018;21:75-82)

The suture is continued posteriorly until it reaches the margins of the ventriculotomy. A patch of homograft (or pericardium or synthetic patch) is cut to approximately a semi-bullet shape and sutured into place to complete the anterior half of the anastomosis. This is performed using either 5/0 or 4/0 polypropylene suture. The curved upper edge is anastomosed to the homograft and the rest to the ventriculotomy. This anastomosis is often reinforced with some interrupted pledgeted sutures. An alternative technique is described which is used in older children or in redo procedures where the allograft conduit does not have sufficient length ( Fig. 35.16 ).

Alternative method for right ventricular (RV) outflow tract valved conduit placement in tetralogy of Fallot with pulmonary atresia. General operative management is similar to that described in Fig. 35.14 . Using this method, a circumferential polyester conduit is attached to proximal end of allograft valved conduit to facilitate ventricle-to-conduit anastomosis. (A) Dashed lines indicate incisions to be made on central pulmonary artery and on RV infundibulum. (B) Inset shows polyester conduit being connected to proximal end of allograft valved conduit with a running monofilament suture. In main figure, distal anastomosis between allograft conduit and incision in pulmonary trunk is performed, leaving atretic pulmonary trunk intact. Proximal polyester extension of allograft is tailored with a sharp bevel to accommodate its connection to the RV. (C) Beveled free edge of polyester conduit is connected to ventriculotomy to complete operation. As seen here, there may be only several millimeters of length to circumferential component of polyester extension of the conduit, which mostly serves as a proximal hood. PTFE, Polytetrafluoroethylene.

If the repair is in a neonate, caution must be exercised to protect the LAD, which may be close to the anastomosis. The conduit must not be oversized because this can act like a pseudoaneurysm, which may result in a low cardiac output state despite good ventricular function. After reconstruction, rewarming and separation from CPB are identical to that of TOF with PS (see Section I of Chapter 34 ).

This group of patients will include confluent and nonfluent PAs or absent right or left or both PAs with aortopulmonary collateral arteries and sometimes a PDA that supply pulmonary blood flow.

The hallmark of this group is the highly variable vascular (collateral, pulmonary arterial, and dual) blood supply to the lungs. This often dictates the surgical approach along with the expertise available at a given institution. The experience accumulated over more than two decades supported by the follow up studies and several institutional experiences suggest that a majority of patients with PA, VSD, and MAPCAs can be managed with a one-stage unifocalization. This approach can be applied to most categories of patients, as long as the intraparenchymal vessels are acceptable; 80% percent of these can be fully repaired in infancy with one-stage left and right pulmonary unifocalization, VSD closure, and RV outflow tract reconstruction. ^, Individual surgeons sometimes prefer a staged approach. In certain morphologic and physiologic situations, a one-stage repair or unifocalization is contraindicated. These are described later in this chapter. ^{, ,}

Approach to one-stage unifocalization and repair follows several basic principles to achieve a satisfactory repair:

• 1.

  Evaluating and Controlling the Pulmonary Vascular Supply

• 2.

  Managing Cardiopulmonary Bypass

• 3.

  Unifocalization of the Pulmonary Arteries and Collaterals

• 4.

  Assessing Adequacy of Unifocalization: Pulmonary Flow Study

• 5.

  Cardiac Repair: VSD Closure and RV to PA Conduit

• 6.

  Completing and Assessing the Repair

The operation is generally performed between 3 to 6 months of age and sometimes later in infancy if the preoperative assessment reveals that the pulmonary bed is well protected. Very uncommonly a repair is warranted in the neonatal period for significant hypoxia or due to pulmonary over circulation and failure to thrive. Infants with discontinuous PAs, each supplied by a PDA or collateral, should undergo intervention in the neonatal period, unless flow into the MAPCAs is secure, in which case unifocalization can still be planned for 3 to 6 months.

Single-stage repair requires a sternotomy approach, and the initial steps until the pericardium is harvested are similar to those for TOF/PA with confluent PAs.

Evaluating and controlling the pulmonary vascular supply.

With current imaging capabilities, the topography of the pulmonary vascular supply is well established, provided the surgeon has a clear understanding of the PAs, MAPCAs, and their relation to other vascular and mediastinal structures. However, it is not uncommon for intrapericardial hypoplastic PAs to be undetected by imaging, or for some occluded collaterals to be poorly visualized due to retrograde filling. Therefore, it is essential to assess the intrapericardial PAs, if present, and dissect and mobilize them all the way into the pulmonary parenchyma, sometimes extending to their segmental locations.

Next, the collaterals should be evaluated. This requires a thorough study of angiograms and CT scans to develop a clear mental image of the vascular morphology. Intraoperative access to imaging can be beneficial. The preferred approach for dissecting and controlling the collaterals is through the mediastinum as suggested by Tchervenkov and associates and only rarely through the pleural cavities. Dissection is performed via the transverse pericardial sinus in the subcarinal region, between the aorta and superior vena cava (SVC), and between the ascending and descending aorta (see Fig. 35.17 ).

Anatomy of tetralogy of Fallot with pulmonary atresia, hypoplastic confluent central pulmonary arteries, and large aortopulmonary collateral arteries. This illustration provides a single example; however, it should be emphasized that extreme variability in number, origin, course, and size of large collateral arteries and true pulmonary arteries is found. Small pulmonary trunk extends to atretic pulmonary valve and is physically connected to the infundibulum. True pulmonary arteries are confluent and severely hypoplastic, and these central pulmonary arteries have limited distribution to the lungs. True left pulmonary artery (LPA) bifurcates to upper lobe and lingula only, and true right pulmonary artery (RPA) distributes to upper and middle lobes only. Three collateral vessels are present: one distributes to left lower lobe (APC1) and two distribute to right lung, one to right upper lobe (APC2) and one to right lower lobe (APC3) . Note that APC2 communicates with upper branch of true RPA, whereas APC1 and 3 have no proximal communication to true RPA and LPA. Thus, right upper lung field is said to have “dual-supply” blood flow from both collateral system (APC2) and true RPA, while left upper lung field has isolated blood supply from true LPA, and right lower lobe and left lower lobe have isolated blood supply, each from one collateral. Prior to beginning cardiopulmonary bypass (CPB), true pulmonary arteries and all major collaterals are identified at their origin and dissected throughout their course until the vessels enter lung parenchyma. This often requires extensive dissection. Although collateral arteries may arise from many systemic arterial sites (see text for detailed description), the most common site of origin is the upper descending thoracic aorta, as illustrated. These collaterals are best identified, dissected, and rerouted for unifocalization by working through the central mediastinum as shown. Based on evaluation of preoperative angiograms, it may be beneficial to dissect and identify all major communications between collateral vessels and true pulmonary arteries. As illustrated, ascending aorta is retracted anteriorly and to the left, either with a rigid retractor or a heavy stay suture placed into the adventitia. Superior vena cava (SVC) is mobilized completely, and commonly the azygos vein is ligated and divided. SVC is then retracted laterally to the right. This exposes the central mediastinum in the midline. If true central pulmonary arteries are present, these are fully dissected first so that they can be mobilized, allowing direct dissection into central mediastinum. To accomplish this, the pericardial reflection in the transverse sinus is opened in the midline, and space below tracheal bifurcation and above dome of left atrium is entered. Dissection transitions from central to posterior mediastinum, and upper thoracic descending aorta and esophagus are completely exposed. Collateral arteries are encountered in this dissection, and their origins from the upper thoracic aorta are easily identified. These collaterals are then dissected along their entire course until they enter lung parenchyma. It should be noted that collateral arteries commonly pass superficially through esophageal musculature; this must be recognized during the process of collateral dissection to avoid injuring the esophagus. Collaterals are commonly intertwined with secondary vagal nerve fibers, and it may be necessary to divide these to fully mobilize the collateral arteries. Once true pulmonary arteries and all collateral vessels have been fully identified and mobilized, preparation is made for CPB. Ao, Aorta; APC, aortopulmonary collateral artery; PT, pulmonary trunk; T, trachea.

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