World Journal for Pediatric and Congenital Heart Surgery http://pch.sagepub.com/
Management of Tetralogy of Fallot With Unilateral Absence of Pulmonary Artery: An Overview Balram Babu and Christopher A. Caldarone World Journal for Pediatric and Congenital Heart Surgery 2014 5: 70 DOI: 10.1177/2150135113506597 The online version of this article can be found at: http://pch.sagepub.com/content/5/1/70
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Review Article
Management of Tetralogy of Fallot With Unilateral Absence of Pulmonary Artery: An Overview
World Journal for Pediatric and Congenital Heart Surgery 2014, Vol 5(1) 70-79 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/2150135113506597 pch.sagepub.com
Balram Babu, MCh1, and Christopher A. Caldarone, MD2
Abstract Tetralogy of Fallot with unilateral absence of pulmonary artery (PA) is a rare congenital anomaly that has been reported in isolated case reports and small case series. There is no well-defined treatment algorithm for these patients, and repair has been associated with high mortality, although survival is improving in the more recent era. Recent reports suggest strict case selection criteria based on PA dimensions and size of the left ventricle. Keywords tetralogy of Fallot, unilateral absence of pulmonary artery, cyanotic heart disease, Nakata index Submitted June 02, 2013; Accepted August 21, 2013.
Introduction Tetralogy of Fallot (TOF) with unilateral absence of pulmonary artery (UAPA) is a rare congenital anomaly, and the ideal management is a matter of debate. The literature available is limited to isolated case reports and small case series. There is no welldefined treatment algorithm for such cases and they still represent a surgical challenge. The surgeon is often faced with the difficult challenge of deciding among the treatment options of the ideal two-lung repair, single-lung repair, or palliative operations. This review has tried to classify the spectrum of this anomaly, describe the pathophysiology in detail, and discuss the management options in a systematic manner, which will be helpful for decision-making process.
Definition The UAPA is an anomaly with complete absence of the intrapericardial segment of one of the main pulmonary artery (PA) branches. It was first reported by Fraentzel in 1868.1 The UAPA generally occurs in patients with situs solitus and concordant atrioventricular and ventriculoarterial connections. According to Kucera and colleagues,2 the incidence of UAPA is 0.6%. Of the patients, 40% has the isolated form of lesion, whereas in 60% of the cases, UAPA is combined with other congenital heart defects. The TOF is the most frequent concomitant disorder of UAPA. The TOF was present in 17 patients of a series of 98 patients with UAPA, reported by Pool and his associates.3 The reported incidence of UAPA varies from 0.95% to 3.23% among patients with TOF.4-6 Interestingly
enough, the left PA (LPA) is absent five to eight times more frequently than the right one.2,5,6 Approximately 100 patients with TOF with UAPA have been reported in the literature.5-12 Acquired unilateral atresia of PA has been reported secondary to ductus closure.13 Iatrogenic unilateral atresia has also been reported secondary to previous systemic to PA shunts.13
Embryology Several theories have been introduced to explain this lesion. According to the theory of involution of the sixth aortic arch, the absorption of either the right or the left arch leads to the absence of one of the main pulmonary branches.7,14 The concept, however, does not explain frequent association of agenesis of the LPA with TOF or why the absence of the right PA (RPA) is usually not associated with other congenital heart defects. According to the ontogenetic theory, the absence of one of the pulmonary arteries is caused by abnormal septation of the truncus.15 Dorsal shift of either the right or the left truncal ridges results in agenesis of the RPA or LPA, correspondingly. The theory successfully explains the fact that agenesis 1 Department of Cardiothoracic Surgery, Apollo Hospitals, Bangalore, Karnataka, India 2 Division of Cardiac Surgery, Hospital for Sick Children and University of Toronto, Toronto, Canada
Corresponding Author: Balram Babu, Department of Cardiothoracic Surgery, Apollo Hospitals, 154/11, Bannerghatta Road, Bangalore, 560076, Karnataka, India. Email: [email protected]
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Abbreviations and Acronyms CPB LA LPA LV MRI PA PVR RPA RV RA RVOT RVSP TOF UAPA VSD
cardiopulmonary bypass left atrial left pulmonary artery left ventricle Magnetic resonance imaging pulmonary artery pulmonary vascular resistance right pulmonary artery right ventricle right atrium right ventricular outflow tract right ventricle systolic pressure Tetralogy of Fallot unilateral absence of pulmonary artery ventricular septal defect
of the RPA is most often an isolated anomaly as well as why a frequent association of TOF with the absence of the LPA does occur. However, the concept fails to explain the rare association of TOF with agenesis of the RPA.
Classification The following classification system is proposed for the spectrum of this disease (Figure 1), which is essential for planning management. These cases may be broadly divided into four types. Type 1: There is absent ipsilateral hilar PA, and the entire lung on the ipsilateral side is supplied by multiple collaterals from aorta or its branches. Branch PA (see note 1, page 78) is absent on the ipsilateral side (note 2). Type 2: There is adequate reformation of hilar PA on the affected side which is supplied by multiple collaterals from aorta or its branches. Branch PA is absent on the ipsilateral side. Type 3: There is adequately formed branch PA on the ipsilateral side which is supplied by ductus arteriosus or collaterals. Type 4: Well-developed branch PA on the ipsilateral side which is directly connected to the aorta. (anomalous origin of unilateral PA from the aorta).
Diagnosis and Evaluation During the evaluation of a TOF case, a chest x-ray with unilateral gross arborization abnormality may hint toward such a condition (Figure 2). The echocardiogram shows absent or poor visualization of the main PA on the ipsilateral side. Cardiac catheterization with a right ventricle (RV) injection shows the PA continuous with a branch PA to one lung with absence of a direct connection to the contralateral lung (Figure 3). The branch PA on the affected side is usually not visualized or may fill up late if there is distal reformation. Pulmonary vein wedge injection may demonstrate whether there
is adequate reformation in the hilum or not. An aortogram shows the arterial supply to the affected side which may arise from multiple collaterals, a patent ductus arteriosus, or a welldeveloped PA arising from the aorta (anomalous origin of unilateral PA from aorta). It is also important to look for any stenosis at the origin of the major collaterals or anomalously arising PA, as it is important in deciding the further course of management. A computed tomography angiogram with reconstruction (Figure 4) will give the three-dimensional arrangement of blood supply to the affected lung, which is important for surgical planning. Magnetic resonance imaging (MRI) blood flow studies using phase-contrast velocity mapping and MRI oximetry along with pressure measurement from cardiac catheterization is useful in assessing the stage of pulmonary vascular disease and adequacy of PA raw materials in the affected lung.16,17
Management Management options in such cases may be broadly divided into four categories. (1)
(2)
(3)
(4)
Single-lung repair: ventricular septal defect (VSD) closure þ right ventricular outflow tract (RVOT) reconstruction. The entire RV outflow is directed to the normally connected contralateral lung, and the ipsilateral lung is left connected to the systemic circulation. Double-lung repair: VSD closure þ RVOT reconstruction þ incorporation blood supply of ipsilateral lung to the reconstructed main PA arising from the RVOT. Palliative operations: systemic to PA shunting, RVOT balloon dilatation, or RVOT palliative reconstruction with an open VSD. Nonintervention.
Single-Lung Repair Ventricular septal defect closure along with complete relief of RVOT obstruction, allowing the entire RV outflow to flow into contralateral normally connected lung. The ipsilateral lung is left connected to the aorta and hence to the systemic circulation. This is the most feasible option in most of the type 1 cases and in all the cases who present late in life with advanced pulmonary vascular disease in the ipsilateral lung. However, there are two important prerequisites for this repair. (1)
Normal-sized contralateral PA.
According to Bockeria and associates,12,18 primary complete repair is indicated in patients with a normal size of the contralateral PA (Nakata index Z score more than 2 and Nakata index 336 þ 63 mm2/m2) or its mild hypoplasia (Nakata
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Figure 1. Line diagram showing the different types of TOF with UAPA. TOF indicates tetralogy of Fallot; UAPA, unilateral absence of pulmonary artery.
index Z score equal to or less than 2 but more than 4 and Nakata index 240 þ 21 mm2/m2). Complete repair in patients with a moderate hypoplasia of the contralateral PA (Nakata index more than 6 but less than or equal to 4 and Nakata index 180 þ 7 mm2/m2) is associated with a higher risk. These patients will benefit from a staged approach when a palliative operation is performed as the first intervention. A staged approach is the only choice for patients with severe hypoplasia of the contralateral PA (Nakata index Z score less than 6 and Nakata index 87 þ 40 mm2/m2). According to Zang and associates,6 the diameter of the PA on contralateral side should be 1.5 times that of the descending aorta at the diaphragmatic plane.
(2)
A well-developed left ventricle (LV): left ventricular end-diastolic volume index more than 30 mL/m2.6
In patients not satisfying the above-mentioned criteria, it is safer to undergo an initial palliative procedure and proceed to single-lung repair in a staged manner.
Physiologic Basis for Single-Lung Repair The primary concern regarding single-lung repair is whether the single lung will be able to handle the full RV output, especially in a patient with TOF. Evidence from clinical and experimental studies confirmed that unilateral pulmonary vessels
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Figure 2. Chest x-ray of TOF with UAPA. TOF indicates tetralogy of Fallot; UAPA, unilateral absence of pulmonary artery.
Figure 4. CT angiogram with reconstruction showing MPA continuing as RPA, absent LPA, and collateral supply to left lung. CT, computed tomography; LPA, left pulmonary artery; MPA, main pulmonary artery; RPA, right pulmonary artery.
Figure 3. Cardiac catheterization. RV injection showing MPA continuing as RPA and absent LPA. LPA indicates left pulmonary artery; MPA, main pulmonary artery; RV, right ventricle; RPA, right pulmonary artery.
could endure the total cardiac output with normal or slightly elevated pulmonary pressure.19 There is evidence from postpneumonectomy patients that the single lung can handle systemic output with only moderate increase in RV pressure.20 However, TOF with UAPA subset of patients have certain unique physiological characteristics, which make them different from all other subsets of single lung physiology. Patients with TOF have a tendency for diffuse PA thrombosis and increased pulmonary vascular resistance.21 The lung
bed protected by pulmonary stenosis may respond with vasospasm in the immediate postrepair period.22 Pulmonary vascular and alveolar development may be abnormal in patients with TOF.23,24 Moreover, when one lung is lost from the pulmonary circuit, where both lungs are like resistors connected in parallel (1/R ¼ 1/R1 þ 1/R2), the pulmonary vascular resistance doubles. All these factors increase the pulmonary vascular resistance and the RV afterload. However, there is a unique physiological mechanism in TOF with UAPA, which may protect the RV from failure after a single-lung repair. The ipsilateral anomalous lung, which is connected in parallel to the systemic circulation, steals a significant portion of the systemic cardiac output and circulates it in the aortaipsilateral lung-left atrial (LA) circuit. So the systemic cardiac output and hence the blood returning to right atrium (RA)-RV-PA-single contralateral lung-LA circuit are much lesser in TOF with UAPA, unlike other cases with single-lung physiology. Pressure (P) ¼ flow (I) resistance(R) The RV systolic pressure (RVSP) ¼ systolic PA pressure when there is no RVOT gradient (eg, after RVOT reconstruction) RVSP ¼ transpulmonary valve flow pulmonary vascular resistance (PVR). Assuming that PVR in the single contralateral lung is constant, RVSP is proportional to transpulmonary valve flow
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Since the transpulmonary valve flow is reduced in these cases, RVP is also less, protecting the RV from failure. This physiologic mechanism has multiple implications. (1)
(2)
(3)
(4)
(5)
Closure of the VSD will eliminate any right to left flow at the VSD level. In patients with right to left flow, VSD closure will increase the transpulmonary valve flow and therefore further increase RVSP and chance of RV failure if PA anatomy is inadequate. The ipsilateral lung connected to the systemic circulation decompresses the RA-RV-PA-contralateral single-lung circuit, thus reducing the RV pressures and chances of RV failure. It may be dangerous to connect the ipsilateral side lung to the pulmonary circulation, if it is harboring irreversible pulmonary vascular disease. Because of the high PVR, there may not be any effective flow in ipilateral lung connected to pulmonary circulation, leading to all the flow being directed to the contralateral normally connected lung. Hence, the decompressing effect of the ipsilateral lung connected to the systemic circuit is lost. The chance of high RV pressures, RV failure, and mortality may be high in such a situation. So it is very important that, before attempting to connect the ipsilateral side to the pulmonary circulation, the chance of it harboring irreversible pulmonary vascular disease should be completely ruled out. There is persistent LV volume overload. So the chance of LV failure and mortality is high if the LV volume is low preoperatively. The chance of late LV failure is also high. The systemic cardiac output will be less, leading to decreased exercise tolerance.
Majority of the repairs reported for TOF with UAPA in the literature are single-lung repairs. The operative mortality in the earlier reports was 44% to 48%. 25 Eight cases were reported by Turinetto and colleagues26 and only one survived. Williams and associates22 believed that it could be treated with systemic pulmonary arterial shunting. In 1993, Liu et al reported a series of 23 patients with a mortality of 8.6%. Both the deaths were due to decreased LV size. In 1997, Zhang et al6 reported a series of 24 patients with a mortality of only two (8.3%) patients. They emphasized the importance of the size of contralateral PA and an adequate size LV for a successful repair. Bockeria and associates in 2007 reported complete repair in 20 patients with a mortality of only 5%. They proposed a selection criterion based of Nakata index and Z values of contralateral PA in deciding primary complete repair or a staged procedure. It is noticeable that in majority of the earlier reports with high mortality, there was no mention of the contralateral PA size or LV adequacy. Many authors have reported that if a transannular patch is needed, the use of monocusp valve or a valved conduit (in cases where there is left anterior descending artery crossing RVOT) may be advantageous in single-lung repairs. Valve helps in preventing RV volume overload and failure.12,27 It may be useful
to leave a patent foramen ovale or create a small atrial septal defect in cases with moderate PA hypoplasia.12 Postrepair peak RV to LV pressure assessment should be done, and VSD patch fenestration should be considered in cases with high-peak RV pressures. A peak RV pressure of less than 0.9 may be acceptable in a stable patient.28 Both provide for better systemic cardiac output at the expense of desaturation. Another important issue is the management of perfusion pressures and intracardiac returns on bypass. Adequate preoperative identification and intraoperative control of major collaterals supplying the ipsilateral lung is essential. Dissection and temporary clamping is a useful option. Venting the LV through right superior pulmonary vein is essential during cardiopulmonary bypass (CPB). Cooling the patient on bypass is also a useful adjunct to reduce systemic oxygen consumption. Inadequate CPB due to underestimation of systemic to pulmonary collaterals and inadequate control of these collaterals can lead to operative mortality.12 Although the placement of an LV vent will reduce the risk of pulmonary edema and myocardial injury from distention, it does not prevent the problem of global hypoperfusion and end-organ injury secondary to steal. Using a PH stat blood gas strategy during CPB may be beneficial due to the opposite effects of carbon dioxide on cerebral and pulmonary circulation. This provides sufficient cerebral oxygenation, more uniform brain cooling, decreased systemic pulmonary collateral circulation, lower lactate levels, and improved neurodevelopmental outcomes during hypothermic CPB.29,30,31 Other strategies like high-flow bypass, maintaining high hematocrit (30%-35%), avoiding deep hypothermic circulatory arrest, and preventing reoxygenation injury may also be beneficial for end-organ protection.30,31,32 Maintaining higher hematocrit (35%) has been demonstrated to have higher perfusion pressures, which may be particularly beneficial in this subset of children.31
Long-Term Fate of Single-Lung Repair There are few published long-term studies about the fate of single-lung repair. Zhang et al6 followed-up 22 patients for a period ranging from 6 months to 15 years (mean, 7.25 years); only one patient died eight years after the operation without clear cause, and 21 patients could move freely without the symptoms of cyanosis or administration of cardiotonic and diuretic drugs. Imanaka and associates, in a case report of VSD with absent LPA, who underwent single-lung repair at two months of age, have reported massive unremitting hemoptysis which required pneumonectomy at 11 months of age.33 Rene and associates have reported two cases of unilateral absence of PA presenting with hemoptysis and was treated by coil embolization.34 Since there are no long-term studies about the fate of such repair with one lung connected to systemic and another one to pulmonary circulation, a theoretical explanation about the fate of such repair is as follows. The normally connected contralateral lung initially adjusts to the increased blood flow by vasodilatation,35 and the decrease of blood viscosity and dissolution of the microthrombus may
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gradually decrease the resistance of the pulmonary blood vessels.6 Repair early in life can promote lung growth in TOF.24 Moreover, evidence from postpneumonectomy models shows satisfactory growth in the single lung.36 So the RV pressures may come down from the immediate postsurgical period and they may settle with mild to moderate RV hypertension.20 Right lung single-lung repairs should perform better than left lung single-lung repairs, considering the larger size. The unprotected areas of the ipsilateral lung connected to systemic circulation lung will continue to have progressive increase in PVR, and the flow in that circuit may reduce over time. The patient may start experiencing sequela of irreversible pulmonary vascular disease in ipsilateral lung, like hemoptysis. In the meanwhile, blood flow to the contralateral normally connected lung in the pulmonary circuit gradually increases due to the adaptive mechanisms described earlier. At this stage, it may be safe to proceed with coil embolization of the major collaterals supplying the ipsilateral lung, or even considering pneumonectomy, as the normal lung would have adjusted for the increased blood flow by this time. Taking down the flow through the ipsilateral lung at this stage may also help in reducing LV volume overload. The lung connected to systemic circulation is also susceptible for recurrent infections.28 Pneumonectomy may be the only feasible option for a nonrecruitable ipsilateral lung with sequelae of irreversible pulmonary vascular disease or recurrent infections.34,37 However, pneumonectomy is not advisable as a single-stage procedure along with single-lung repair, as it increases the chance of RV failure and is best performed at a later stage.
Double-Lung Repair Ideal double-lung repair involves a complete anatomical and physiologic correction including VSD closure, relief of RVOT obstruction, and incorporating the ipsilateral lung into the pulmonary circulation. However, there are important prerequisites for such a repair. Candidates for double-lung repair should have: (1)
(2)
A well-developed ipsilateral hilar PA, which is present in type 2, 3, and 4 of this disease. In type 1, unifocalization of the ipsilateral lung is an option when there is sufficient development of the collaterals to allow unifocalization. Absence of irreversible pulmonary vascular disease in the ipsilateral side.
Severe pulmonary vascular disease has been reported as early as three months of age with anomalous origin of PA from the aorta.38 Assessment of pulmonary hypertension in the ipsilateral lung may require catheterization for pressure measurements (if there is proximal stenosis) and MRI to measure single-lung pulmonary blood flow. Stenosis of anomalous pulmonary vasculature may protect against the development of pulmonary vascular disease. (3)
Adequate sized PA anatomy after reconstruction: after connecting the ipsilateral lung to the main pulmonary
system, an assessment must be made regarding whether the PA system will have adequately low resistance to allow intracardiac repair and VSD closure. Objective assessment can be made using an intraoperative blood flow study.39 The MRI-based assessment looks promising for preoperative noninvasive assessment of PA system.17 Mean PA pressures of up to 25 to 30 mm Hg at full indexed cardiac output usually indicate the ability to move ahead with VSD closure. If the pressures are high, the patient should undergo a staged procedure with an initial repair with open or fenestrated VSD. Double-lung repair has been reported less frequently and mostly described in neonates with isolated UAPA.40-44 Murphy and associates45 have reported three cases of TOF with UAPA. One was a patient with TOF with absent pulmonary valve with absent LPA, which underwent a first stage 8-mm graft reconnection of affected LPA to RPA at three months of age. The second stage correction was done at 33 months, using a homograft conduit and 12-mm graft to LPA. The other two patients with TOF with UAPA underwent initial systemic shunt to affected LPA using 5-mm synthetic shunt at two months and six days of age, respectively, and underwent complete repair at 11 months and 20 months of age, respectively, with direct anastomosis of LPA to main pulmonary trunk. They were able to demonstrate that with an early recruitment, there is evidence of good growth of the affected PA with restoration of nearnormal perfusion to the left lung. Prifti et al has reported successful single-stage repair of a patient with TOF and anomalous origin of RPA from ascending aorta, at 18 days of age.46 Talwar and associates47 have reported two cases of TOF with UAPA with double aortic arch who underwent successful single-stage repair at 9 years and 12 years of age respectively. They used homograft saphenous vein in one case and homograft iliac artery in the second case for connecting the LPA to main PA. However, they have not commented about their assessment of the size of the reconstructed PA system and the stage of pulmonary vascular disease in the ipsilateral lung.
Palliative Operations Palliative operations are indicated for patients who are not suitable for the ideal complete two-lung repair or single-lung repair due to inadequate PA anatomy or LV size. They usually serve as the first-stage operation for patients requiring a staged approach to a complete repair or single-lung repair. Palliative procedures relieve cyanosis and polycythemia, prepare the contralateral lung for repair, and promote PA growth LV growth.18,20 Bockeria and associates18 have proposed the following classification system for palliative procedures in TOF with UAPA: Group 1: interventions that are aimed at increasing blood flow in the contralateral lung. These interventions include shunts between the systemic arterial tree and the ipsilateral PA or pulmonary trunk, reconstruction
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World Journal for Pediatric and Congenital Heart Surgery 5(1) of the RVOT without VSD closure, and transluminal balloon pulmonary valvuloplasty. Group 1 interventions are indicated in patients who are not suitable for single-lung repair due to inadequate PA anatomy or poor LV size. Bockeria et al18 reported 29 patients and 32 interventions from 1983 to 2011 with inhospital mortality rates of 7%. Of those patients, whose PA growth was adequate after initial palliation, 59% of the patients underwent a second-stage complete repair. They demonstrated that palliative reconstruction of RVOT provides more significant and uniform enlargement of the PA than systemic to pulmonary shunts or transluminal balloon pulmonary valvuloplasty. They suggested that systemic-to-PA shunt and transluminal balloon pulmonary valvuloplasty are methods of choice in patients with nonsevere hypoplasia of the contralateral PA. Balloon valvuloplasty is indicated more in patients with a prevailing valvular component of the pulmonary stenosis. Palliative reconstruction of the RVOT is a more favorable procedure for patients with a severe hypoplasia of the contralateral PA. Before this important series, the reported worldwide experience with similar palliative interventions is limited only to around 32 cases with an overall mortality of 22%. Most of the reports are isolated case reports with only very few centers having experience of 3 to 4 interventions.8,9,44,45 Group 2: interventions that are aimed to increase blood flow in ipsilateral lung or both lungs. They can be divided into group A and group B. (A)
(B)
Interventions that provide an increase in blood flow in the ipsilateral lung only include shunts between the subclavian artery and the hilar artery of the ipsilateral lung, creation of a communication between the pulmonary trunk and the hilar artery of ipsilateral lung, and any combination of these two procedures. Interventions that provide simultaneous increase in blood flow in both lungs. These interventions include placement of shunts between the systemic arterial tree and the contralateral PA in combination with a shunt between the systemic arterial tree and the hilar artery of ipsilateral lung, shunts between the subclavian artery and the contralateral PA in combination with creation of a communication between the pulmonary trunk and the hilar artery of ipsilateral lung, and creation of a communication between the pulmonary trunk and the hilar artery of ipsilateral lung in combination with palliative reconstruction of the RVOT.
Group 2 interventions are indicated in patients whose PA anatomy is inadequate for one-stage, double-lung repair. They help in promoting PA growth so that they can endure the complete cardiac output at the time of complete repair. Such palliations45 have been reported as a staged approach toward the ideal two-lung repair.
Nonintervention: Considering the high-perioperative mortality reported in many series,24,26 the surgeon may opt for no intervention at all. The anomalous circulation to the ipsilateral lung may provide freedom from cyanosis depending on the amount of pulmonary blood flow. The long-term problems are likely to be determined by progression of pulmonary hypertension in the ipsilateral lung and the degree of obstruction in the RVOT supplying the contralateral lung. Depending on these factors, consequences of UAPA may range from volume overload and congestive heart failure to progressive cyanosis. Some patients may be fortuitously well balanced. However, the natural history of this anomaly is not well elucidated. According to Williams et al,22 the untreated patients lead extremely restricted lives, and although the number of such patients with adequate follow-up is small, most die by 12 to 14 years. It is difficult to frame definite opinion about noninterventional management with the available data. Patients who present later in life with minimal cyanosis and mild symptoms may be candidate for nonintervention, especially those with nonreconstructable ipsilateral PA, with or without irreversible pulmonary vascular disease and a small sized contra lateral branch PA. It is reasonable to intervene in most other cases.
Timing of Repair The following factors demand consideration in determining the timing of repair: (1) Avoid development of pulmonary vascular disease and also loss of highly stenotic collaterals in the affected lung, (2) promote normal lung growth, (3) avoid long-term effects of cyanosis and RV hypertension, (4) risk of higher perioperative mortality while operating at a very young age, (5) unfavorable natural history (risk of dying during the waiting period), (6) institutional experience in managing small children, and (7) clinical status (cyanosis/overcirculation and failure). Surgical correction during early infancy is recommended in majority of type 1 and type 2 cases,48 with neonatal correction reserved for cases with hemodynamic instability (overcirculation/severe cyanosis), ductus supplying the disconnected pulmonary, or anomalous origin of a PA from aorta.46,48,49
Conclusion Tetralogy of Fallot with unilateral absence of PA can be surgically treated with acceptable morbidity and mortality, and adherence to strict selection criteria (Figure 5) is the key to success. Patients who present with a reconstructable ipsilateral PA and absence of irreversible pulmonary vascular disease in the ipsilateral lung should be considered for the double-lung repair. A single step or staged repair depends on the size and resistance of the PA system after reconstruction. Those with nonreconstructable ipsilateral PA and those who present late with irreversible pulmonary
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Figure 5. Flowchart for management of TOF with UAPA. TOF indicates tetralogy of Fallot; UAPA, unilateral absence of pulmonary artery.
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vascular disease should be planned for single-lung repair. An adequate sized contralateral PA and LV is a prerequisite for singlestage repair. Patients with small contralateral PA or LV should be offered an initial palliative procedure, followed by periodic reassessment of PA and LV size. Those with adequate growth of PA or LV may become candidates for single-lung correction. The option of nonintervention should be individualized based on the clinical presentation and feasibility for repair. Long-term follow-up studies with larger groups of patients are needed to refine treatment options for patients with TOF with UAPA. Acknowledgments
11.
12.
13.
14.
The authors thank Dr Adil Sadiq, consultant cardiac surgeon, Apollo Hospitals, Bangalore, for his illustrations. 15.
Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
16.
Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.
17.
Notes Note 1: branch PA refers to LPA or RPA. Note 2: ipsilateral refers to the side in which branch PA is disconnected or absent, and contralateral refers to the normal side. 18.
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pulmonary artery in continuity with the right ventricular outflow tract. Surgery. 1973;74(6): 887-893. Laborde F, de Riberolles C, Escande G, Lino R, Hazan E, Neveux JY. Tetralogy of fallot with congenital absence of a pulmonary artery. Apropos of 4 cases[in French]. Sem Hop. 1983;59(44): 3043-3046. Bockeria LA, Podzolkov VP, Makhachev OA, et al. Surgical correction of tetralogy of Fallot with unilateral absence of pulmonary artery. Ann Thorac Surg. 2007;83(2): 613-618. Waldman JD, Karp RB, Gittenberger-de Groot AC, Agarwala B, Glagov S. Spontaneous acquisition of discontinuous pulmonary arteries. Ann Thorac Surg. 1996;62(1): 161-168. Sherrick DW, Kincaid OW, Dushane JW. Agenesis of a main branch of the pulmonary artery. Am J Roentgenol Radium Ther Nucl Med. 1962;87: 917-928. Cucci CE, Doyle EF, Lewis EW Jr. Absence of a primary division of the pulmonary trunk: an ontogenetic theory. Circulation. 1964; 29: 124-131. Grosse-Wortmann L, Al-Otay A, Goo HW, et al. Anatomical and functional evaluation of pulmonary veins in children by magnetic resonance imaging. J Am Coll Cardiol. 2007;49(9): 993-1002. Honjo O, Al-Radi OO, Macdonald C, et al. The functional intraoperative pulmonary blood flow study is a more sensitive predictor than preoperative anatomy for right ventricular pressure and physiologic tolerance of ventricular septal defect closure after complete unifocalization in patients with pulmonary atresia,ventricular septal defect and major aortopulmonary collaterals. Circulation. 2009; 120(suppl 10): S46-S52. Bockeria LA, Podzolkov VP, Makhachev OA, et al. Palliative surgical treatment of congenital heart defects associated with unilateral absence of the pulmonary artery. Interact Cardiovasc Thorac Surg. 2013;16(3): 286-292. Werber J, Ramilo JL, London R, Harris VJ. Unilateral absence of pulmonary artery. Chest. 1983;84(6): 729-732. Deslauriers J, Ugalde P, Miro S, et al. Adjustments in cardiorespiratory function after pneumonectomy: results of the pneumonectomy project. J Thorac Cardiovasc Surg. 2011;141(1): 7-15. Ferencz C. The pulmonary vascular bed in tetralogy of Fallot. I. Changes associated with pulmonic stenosis. Bull Johns Hopkins Hosp. 1960;106:81-99. Williams GD, Dungan WT, Campbell GS. Surgical treatment of tetralogy of Fallot with unilateral absence of a pulmonary artery. Ann Thorac Surg. 1972;14(5): 483-493. Hislop A, Reid L. Structural changes in pulmonary arteries and veins in Tetralogy of Fallot. Br Heart J. 1973;35(11): 1178-1183. Johnson RJ, Haworth SG. Pulmonary vascular and alveolar development in tetralogy of Fallot: a recommendation for early correction. Thorax. 1982;37(12):893-901. Mistrot JJ, Bernhard WF, Rosenthal A, Castan˜eda A. Tetralogy of Fallot with a single pulmonary artery: operative repair. Ann Thorac Surg. 1977;23(3): 249-253. Turinetto B, Colı` G, Donati A, Galli R, Mikus P, Pierangeli A. Absent right pulmonary artery complicating tetralogy of Fallot. J Cardiovasc Surg (Torino). 1975;16(3): 322-326. Goldsmith M, Farina MA, Shaher RM. Tetralogy of Fallot with atresia of the left pulmonary artery: surgical repair using a homograft aortic valve. J Thorac Cardiovasc Surg. 1975;69(3): 458-466.
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28. Kouchoukos NT, Blackstone EH, Doty DB, Hanley FL, Karp RB. Ventricular septal defect with pulmonary stenosis or atresia. In: Kouchoukos NT, Blackstone EH, Doty DB, Hanley FL, Karp RB. Kirklin/Baratt-Boyes Cardiac Surgery. 3rd ed. Philadelphia, PA: Elsevier Science; 2003:1030. 29. Sakamoto T, Kurosawa H, Shin’oka T, Aoki M, Isomatsu Y. The influence of pH strategy on cerebral and collateral circulation during hypothermic cardiopulmonary bypass in cyanotic patients with heart disease: results of a randomized trial and real-time monitoring. J Thorac Cardiovasc Surg. 2004;127(1): 12-19. 30. Nelson DP, Andropoulos DB, Fraser CD Jr. Perioperative neuroprotective strategies. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2008;11(1): 49-56. 31. Newburger JW, Jonas RA, Soul J, et al. Randomized trial of hematocrit 25% versus 35% during hypothermic cardiopulmonary bypass in infant heart surgery. J Thorac Cardiovasc Surg. 2008; 135(2): 347-354. 32. Babu B, Bhat S, Prabuswamy HP, et al. Controlling oxygenation during initiation of cardiopulmonary bypass: can it improve immediate postoperative outcomes in cyanotic children undergoing cardiac surgery? A prospective randomized study. World J Pediatr Congenit Heart Surg. 2012;3(3): 310-316. 33. Imanaka K, Shimizu S, Matsumoto J, Hashizume K, Tsuchiya K, Takemura T. Unilateral absence of pulmonary artery and ventricular septal defect in an infant. Ann Thorac Surg. 1998;66(1): 251-252. 34. Ren˜e´ M, Sans J, Dominguez J, Sancho C, Valldeperas J. Unilateral pulmonary artery agenesis presenting with hemoptysis: treatment by embolization of systemic collaterals. Cardiovasc Intervent Radiol. 1995;18(4): 251-254. 35. Maxey TS, Fernandez LG, Reece TB, Keeling WB, Kron IL, Laubach VE. Endothelial nitric oxide synthase is essential for postpneumonectomy compensatory vasodilation. Ann Thorac Surg. 2006;81(4): 1234-1238. 36. Brown LM, Rannels SR, Rannels DE. Implications of postpneumonectomy compensatory lung growth in pulmonary physiology and disease. Respir Res. 2001;2(6): 340-347. 37. Kadir IS, Thekudan J, Dheodar A, Jones MT, Carroll KB. Congenital unilateral pulmonary artery agenesis and aspergilloma. Ann Thorac Surg. 2002;74(6): 2169-2171. 38. Yamaki S, Suzuki Y, Ishizawa E, Kagawa Y, Horiuchi T, Sato T. Isolated aortic origin of right pulmonary artery. Report of a case
39.
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with special reference to pulmonary vascular disease in the left and right lung. Chest. 1983;83(3): 575-578. Reddy VM, Petrossian E, Mc Elhinney DB, Moore P, Teitel DF, Hanley FL. One-stage complete unifocalisation in infants: when should be the ventricular septal defect be closed? J Thorac Cardiovasc Surg. 1997;113(5): 858-868. Shakibi JG, Rastan H, Nazarian I, Paydar M, Aryanpour I, Siassi B. Isolated unilateral absence of the pulmonary artery. Review of the world literature and guidelines for surgical repair. Jpn Heart J. 1978;19(3): 439-451. Toews WH, Pappas G. Surgical management of absent right pulmonary artery with associated pulmonary hypertension. Chest. 1983;84(4): 497-499. Moreno-Cabral RJ, McNamara JJ, Reddy VJ, Caldwell P. Unilateral absent pulmonary artery: surgical repair with a new technique. J Thorac Cardiovasc Surg. 1991;102(3): 463-465. Kosaka Y, Kurosawa H, Hoshino S, Shin’oka T, Isomatsu Y, Tsuji Y. Surgery for unilateral absence of pulmonary artery using autologous tissue. Ann Thorac Surg. 2003;76(4): 1281-1283. Kim GB, Ban JE, Bae EJ, et al. Rehabilitation of pulmonary artery in congenital unilateral absence of intrapericardial pulmonary artery. J Thorac Cardiovasc Surg. 2011;141(1): 171-178. Murphy DN, Winlaw DS, Cooper SG, Nunn GR. Successful early surgical recruitment of the congenitally disconnected pulmonary artery. Ann Thorac Surg. 2004;77(1): 29-35. Prifti E, Crucean A, Bonacchi M, Bonacchib M, et al. Postoperative outcome in patients with anomalous origin of one pulmonary artery branch from the aorta. Eur J Cardiothorac Surg. 2003; 24(1): 21-27. Talwar S, Gupta A, Choudhary SK, Airan B. Absent left pulmonary artery and double aortic arch in tetralogy of Fallot: reconstruction using homograft saphenous vein or iliac artery. Interact Cardiovasc Thorac Surg. 2009;8(2): 277-279. Malhotra SP, Hanley FL. Surgical management of pulmonaryatresia with ventricular septal defect and major aortopulmonary collaterals: a protocol-based approach. Semin Thorac Cardiovasc Surg Pediatr Card Surg Annu. 2009;12(1): 145-151. Kouchoukos NT, Blackstone EH, Doty DB, Hanley FL, Karp RB. Origin of right or left pulmonary artery from ascending aorta. In: Kouchoukos NT, Blackstone EH, Doty DB, Hanley FL, Karp RB. Kirklin/Baratt-Boyes Cardiac Surgery. 3rd ed. Philadelphia, PA: Elsevier Science; 2003:1233.
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Management of Tetralogy of Fallot With Unilateral Absence of Pulmonary Artery: An Overview Balram Babu and Christopher A. Caldarone World Journal for Pediatric and Congenital Heart Surgery 2014 5: 70 DOI: 10.1177/2150135113506597 The online version of this article can be found at: http://pch.sagepub.com/content/5/1/70
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Review Article
Management of Tetralogy of Fallot With Unilateral Absence of Pulmonary Artery: An Overview
World Journal for Pediatric and Congenital Heart Surgery 2014, Vol 5(1) 70-79 ª The Author(s) 2014 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/2150135113506597 pch.sagepub.com
Balram Babu, MCh1, and Christopher A. Caldarone, MD2
Abstract Tetralogy of Fallot with unilateral absence of pulmonary artery (PA) is a rare congenital anomaly that has been reported in isolated case reports and small case series. There is no well-defined treatment algorithm for these patients, and repair has been associated with high mortality, although survival is improving in the more recent era. Recent reports suggest strict case selection criteria based on PA dimensions and size of the left ventricle. Keywords tetralogy of Fallot, unilateral absence of pulmonary artery, cyanotic heart disease, Nakata index Submitted June 02, 2013; Accepted August 21, 2013.
Introduction Tetralogy of Fallot (TOF) with unilateral absence of pulmonary artery (UAPA) is a rare congenital anomaly, and the ideal management is a matter of debate. The literature available is limited to isolated case reports and small case series. There is no welldefined treatment algorithm for such cases and they still represent a surgical challenge. The surgeon is often faced with the difficult challenge of deciding among the treatment options of the ideal two-lung repair, single-lung repair, or palliative operations. This review has tried to classify the spectrum of this anomaly, describe the pathophysiology in detail, and discuss the management options in a systematic manner, which will be helpful for decision-making process.
Definition The UAPA is an anomaly with complete absence of the intrapericardial segment of one of the main pulmonary artery (PA) branches. It was first reported by Fraentzel in 1868.1 The UAPA generally occurs in patients with situs solitus and concordant atrioventricular and ventriculoarterial connections. According to Kucera and colleagues,2 the incidence of UAPA is 0.6%. Of the patients, 40% has the isolated form of lesion, whereas in 60% of the cases, UAPA is combined with other congenital heart defects. The TOF is the most frequent concomitant disorder of UAPA. The TOF was present in 17 patients of a series of 98 patients with UAPA, reported by Pool and his associates.3 The reported incidence of UAPA varies from 0.95% to 3.23% among patients with TOF.4-6 Interestingly
enough, the left PA (LPA) is absent five to eight times more frequently than the right one.2,5,6 Approximately 100 patients with TOF with UAPA have been reported in the literature.5-12 Acquired unilateral atresia of PA has been reported secondary to ductus closure.13 Iatrogenic unilateral atresia has also been reported secondary to previous systemic to PA shunts.13
Embryology Several theories have been introduced to explain this lesion. According to the theory of involution of the sixth aortic arch, the absorption of either the right or the left arch leads to the absence of one of the main pulmonary branches.7,14 The concept, however, does not explain frequent association of agenesis of the LPA with TOF or why the absence of the right PA (RPA) is usually not associated with other congenital heart defects. According to the ontogenetic theory, the absence of one of the pulmonary arteries is caused by abnormal septation of the truncus.15 Dorsal shift of either the right or the left truncal ridges results in agenesis of the RPA or LPA, correspondingly. The theory successfully explains the fact that agenesis 1 Department of Cardiothoracic Surgery, Apollo Hospitals, Bangalore, Karnataka, India 2 Division of Cardiac Surgery, Hospital for Sick Children and University of Toronto, Toronto, Canada
Corresponding Author: Balram Babu, Department of Cardiothoracic Surgery, Apollo Hospitals, 154/11, Bannerghatta Road, Bangalore, 560076, Karnataka, India. Email: [email protected]
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Abbreviations and Acronyms CPB LA LPA LV MRI PA PVR RPA RV RA RVOT RVSP TOF UAPA VSD
cardiopulmonary bypass left atrial left pulmonary artery left ventricle Magnetic resonance imaging pulmonary artery pulmonary vascular resistance right pulmonary artery right ventricle right atrium right ventricular outflow tract right ventricle systolic pressure Tetralogy of Fallot unilateral absence of pulmonary artery ventricular septal defect
of the RPA is most often an isolated anomaly as well as why a frequent association of TOF with the absence of the LPA does occur. However, the concept fails to explain the rare association of TOF with agenesis of the RPA.
Classification The following classification system is proposed for the spectrum of this disease (Figure 1), which is essential for planning management. These cases may be broadly divided into four types. Type 1: There is absent ipsilateral hilar PA, and the entire lung on the ipsilateral side is supplied by multiple collaterals from aorta or its branches. Branch PA (see note 1, page 78) is absent on the ipsilateral side (note 2). Type 2: There is adequate reformation of hilar PA on the affected side which is supplied by multiple collaterals from aorta or its branches. Branch PA is absent on the ipsilateral side. Type 3: There is adequately formed branch PA on the ipsilateral side which is supplied by ductus arteriosus or collaterals. Type 4: Well-developed branch PA on the ipsilateral side which is directly connected to the aorta. (anomalous origin of unilateral PA from the aorta).
Diagnosis and Evaluation During the evaluation of a TOF case, a chest x-ray with unilateral gross arborization abnormality may hint toward such a condition (Figure 2). The echocardiogram shows absent or poor visualization of the main PA on the ipsilateral side. Cardiac catheterization with a right ventricle (RV) injection shows the PA continuous with a branch PA to one lung with absence of a direct connection to the contralateral lung (Figure 3). The branch PA on the affected side is usually not visualized or may fill up late if there is distal reformation. Pulmonary vein wedge injection may demonstrate whether there
is adequate reformation in the hilum or not. An aortogram shows the arterial supply to the affected side which may arise from multiple collaterals, a patent ductus arteriosus, or a welldeveloped PA arising from the aorta (anomalous origin of unilateral PA from aorta). It is also important to look for any stenosis at the origin of the major collaterals or anomalously arising PA, as it is important in deciding the further course of management. A computed tomography angiogram with reconstruction (Figure 4) will give the three-dimensional arrangement of blood supply to the affected lung, which is important for surgical planning. Magnetic resonance imaging (MRI) blood flow studies using phase-contrast velocity mapping and MRI oximetry along with pressure measurement from cardiac catheterization is useful in assessing the stage of pulmonary vascular disease and adequacy of PA raw materials in the affected lung.16,17
Management Management options in such cases may be broadly divided into four categories. (1)
(2)
(3)
(4)
Single-lung repair: ventricular septal defect (VSD) closure þ right ventricular outflow tract (RVOT) reconstruction. The entire RV outflow is directed to the normally connected contralateral lung, and the ipsilateral lung is left connected to the systemic circulation. Double-lung repair: VSD closure þ RVOT reconstruction þ incorporation blood supply of ipsilateral lung to the reconstructed main PA arising from the RVOT. Palliative operations: systemic to PA shunting, RVOT balloon dilatation, or RVOT palliative reconstruction with an open VSD. Nonintervention.
Single-Lung Repair Ventricular septal defect closure along with complete relief of RVOT obstruction, allowing the entire RV outflow to flow into contralateral normally connected lung. The ipsilateral lung is left connected to the aorta and hence to the systemic circulation. This is the most feasible option in most of the type 1 cases and in all the cases who present late in life with advanced pulmonary vascular disease in the ipsilateral lung. However, there are two important prerequisites for this repair. (1)
Normal-sized contralateral PA.
According to Bockeria and associates,12,18 primary complete repair is indicated in patients with a normal size of the contralateral PA (Nakata index Z score more than 2 and Nakata index 336 þ 63 mm2/m2) or its mild hypoplasia (Nakata
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Figure 1. Line diagram showing the different types of TOF with UAPA. TOF indicates tetralogy of Fallot; UAPA, unilateral absence of pulmonary artery.
index Z score equal to or less than 2 but more than 4 and Nakata index 240 þ 21 mm2/m2). Complete repair in patients with a moderate hypoplasia of the contralateral PA (Nakata index more than 6 but less than or equal to 4 and Nakata index 180 þ 7 mm2/m2) is associated with a higher risk. These patients will benefit from a staged approach when a palliative operation is performed as the first intervention. A staged approach is the only choice for patients with severe hypoplasia of the contralateral PA (Nakata index Z score less than 6 and Nakata index 87 þ 40 mm2/m2). According to Zang and associates,6 the diameter of the PA on contralateral side should be 1.5 times that of the descending aorta at the diaphragmatic plane.
(2)
A well-developed left ventricle (LV): left ventricular end-diastolic volume index more than 30 mL/m2.6
In patients not satisfying the above-mentioned criteria, it is safer to undergo an initial palliative procedure and proceed to single-lung repair in a staged manner.
Physiologic Basis for Single-Lung Repair The primary concern regarding single-lung repair is whether the single lung will be able to handle the full RV output, especially in a patient with TOF. Evidence from clinical and experimental studies confirmed that unilateral pulmonary vessels
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Figure 2. Chest x-ray of TOF with UAPA. TOF indicates tetralogy of Fallot; UAPA, unilateral absence of pulmonary artery.
Figure 4. CT angiogram with reconstruction showing MPA continuing as RPA, absent LPA, and collateral supply to left lung. CT, computed tomography; LPA, left pulmonary artery; MPA, main pulmonary artery; RPA, right pulmonary artery.
Figure 3. Cardiac catheterization. RV injection showing MPA continuing as RPA and absent LPA. LPA indicates left pulmonary artery; MPA, main pulmonary artery; RV, right ventricle; RPA, right pulmonary artery.
could endure the total cardiac output with normal or slightly elevated pulmonary pressure.19 There is evidence from postpneumonectomy patients that the single lung can handle systemic output with only moderate increase in RV pressure.20 However, TOF with UAPA subset of patients have certain unique physiological characteristics, which make them different from all other subsets of single lung physiology. Patients with TOF have a tendency for diffuse PA thrombosis and increased pulmonary vascular resistance.21 The lung
bed protected by pulmonary stenosis may respond with vasospasm in the immediate postrepair period.22 Pulmonary vascular and alveolar development may be abnormal in patients with TOF.23,24 Moreover, when one lung is lost from the pulmonary circuit, where both lungs are like resistors connected in parallel (1/R ¼ 1/R1 þ 1/R2), the pulmonary vascular resistance doubles. All these factors increase the pulmonary vascular resistance and the RV afterload. However, there is a unique physiological mechanism in TOF with UAPA, which may protect the RV from failure after a single-lung repair. The ipsilateral anomalous lung, which is connected in parallel to the systemic circulation, steals a significant portion of the systemic cardiac output and circulates it in the aortaipsilateral lung-left atrial (LA) circuit. So the systemic cardiac output and hence the blood returning to right atrium (RA)-RV-PA-single contralateral lung-LA circuit are much lesser in TOF with UAPA, unlike other cases with single-lung physiology. Pressure (P) ¼ flow (I) resistance(R) The RV systolic pressure (RVSP) ¼ systolic PA pressure when there is no RVOT gradient (eg, after RVOT reconstruction) RVSP ¼ transpulmonary valve flow pulmonary vascular resistance (PVR). Assuming that PVR in the single contralateral lung is constant, RVSP is proportional to transpulmonary valve flow
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Since the transpulmonary valve flow is reduced in these cases, RVP is also less, protecting the RV from failure. This physiologic mechanism has multiple implications. (1)
(2)
(3)
(4)
(5)
Closure of the VSD will eliminate any right to left flow at the VSD level. In patients with right to left flow, VSD closure will increase the transpulmonary valve flow and therefore further increase RVSP and chance of RV failure if PA anatomy is inadequate. The ipsilateral lung connected to the systemic circulation decompresses the RA-RV-PA-contralateral single-lung circuit, thus reducing the RV pressures and chances of RV failure. It may be dangerous to connect the ipsilateral side lung to the pulmonary circulation, if it is harboring irreversible pulmonary vascular disease. Because of the high PVR, there may not be any effective flow in ipilateral lung connected to pulmonary circulation, leading to all the flow being directed to the contralateral normally connected lung. Hence, the decompressing effect of the ipsilateral lung connected to the systemic circuit is lost. The chance of high RV pressures, RV failure, and mortality may be high in such a situation. So it is very important that, before attempting to connect the ipsilateral side to the pulmonary circulation, the chance of it harboring irreversible pulmonary vascular disease should be completely ruled out. There is persistent LV volume overload. So the chance of LV failure and mortality is high if the LV volume is low preoperatively. The chance of late LV failure is also high. The systemic cardiac output will be less, leading to decreased exercise tolerance.
Majority of the repairs reported for TOF with UAPA in the literature are single-lung repairs. The operative mortality in the earlier reports was 44% to 48%. 25 Eight cases were reported by Turinetto and colleagues26 and only one survived. Williams and associates22 believed that it could be treated with systemic pulmonary arterial shunting. In 1993, Liu et al reported a series of 23 patients with a mortality of 8.6%. Both the deaths were due to decreased LV size. In 1997, Zhang et al6 reported a series of 24 patients with a mortality of only two (8.3%) patients. They emphasized the importance of the size of contralateral PA and an adequate size LV for a successful repair. Bockeria and associates in 2007 reported complete repair in 20 patients with a mortality of only 5%. They proposed a selection criterion based of Nakata index and Z values of contralateral PA in deciding primary complete repair or a staged procedure. It is noticeable that in majority of the earlier reports with high mortality, there was no mention of the contralateral PA size or LV adequacy. Many authors have reported that if a transannular patch is needed, the use of monocusp valve or a valved conduit (in cases where there is left anterior descending artery crossing RVOT) may be advantageous in single-lung repairs. Valve helps in preventing RV volume overload and failure.12,27 It may be useful
to leave a patent foramen ovale or create a small atrial septal defect in cases with moderate PA hypoplasia.12 Postrepair peak RV to LV pressure assessment should be done, and VSD patch fenestration should be considered in cases with high-peak RV pressures. A peak RV pressure of less than 0.9 may be acceptable in a stable patient.28 Both provide for better systemic cardiac output at the expense of desaturation. Another important issue is the management of perfusion pressures and intracardiac returns on bypass. Adequate preoperative identification and intraoperative control of major collaterals supplying the ipsilateral lung is essential. Dissection and temporary clamping is a useful option. Venting the LV through right superior pulmonary vein is essential during cardiopulmonary bypass (CPB). Cooling the patient on bypass is also a useful adjunct to reduce systemic oxygen consumption. Inadequate CPB due to underestimation of systemic to pulmonary collaterals and inadequate control of these collaterals can lead to operative mortality.12 Although the placement of an LV vent will reduce the risk of pulmonary edema and myocardial injury from distention, it does not prevent the problem of global hypoperfusion and end-organ injury secondary to steal. Using a PH stat blood gas strategy during CPB may be beneficial due to the opposite effects of carbon dioxide on cerebral and pulmonary circulation. This provides sufficient cerebral oxygenation, more uniform brain cooling, decreased systemic pulmonary collateral circulation, lower lactate levels, and improved neurodevelopmental outcomes during hypothermic CPB.29,30,31 Other strategies like high-flow bypass, maintaining high hematocrit (30%-35%), avoiding deep hypothermic circulatory arrest, and preventing reoxygenation injury may also be beneficial for end-organ protection.30,31,32 Maintaining higher hematocrit (35%) has been demonstrated to have higher perfusion pressures, which may be particularly beneficial in this subset of children.31
Long-Term Fate of Single-Lung Repair There are few published long-term studies about the fate of single-lung repair. Zhang et al6 followed-up 22 patients for a period ranging from 6 months to 15 years (mean, 7.25 years); only one patient died eight years after the operation without clear cause, and 21 patients could move freely without the symptoms of cyanosis or administration of cardiotonic and diuretic drugs. Imanaka and associates, in a case report of VSD with absent LPA, who underwent single-lung repair at two months of age, have reported massive unremitting hemoptysis which required pneumonectomy at 11 months of age.33 Rene and associates have reported two cases of unilateral absence of PA presenting with hemoptysis and was treated by coil embolization.34 Since there are no long-term studies about the fate of such repair with one lung connected to systemic and another one to pulmonary circulation, a theoretical explanation about the fate of such repair is as follows. The normally connected contralateral lung initially adjusts to the increased blood flow by vasodilatation,35 and the decrease of blood viscosity and dissolution of the microthrombus may
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gradually decrease the resistance of the pulmonary blood vessels.6 Repair early in life can promote lung growth in TOF.24 Moreover, evidence from postpneumonectomy models shows satisfactory growth in the single lung.36 So the RV pressures may come down from the immediate postsurgical period and they may settle with mild to moderate RV hypertension.20 Right lung single-lung repairs should perform better than left lung single-lung repairs, considering the larger size. The unprotected areas of the ipsilateral lung connected to systemic circulation lung will continue to have progressive increase in PVR, and the flow in that circuit may reduce over time. The patient may start experiencing sequela of irreversible pulmonary vascular disease in ipsilateral lung, like hemoptysis. In the meanwhile, blood flow to the contralateral normally connected lung in the pulmonary circuit gradually increases due to the adaptive mechanisms described earlier. At this stage, it may be safe to proceed with coil embolization of the major collaterals supplying the ipsilateral lung, or even considering pneumonectomy, as the normal lung would have adjusted for the increased blood flow by this time. Taking down the flow through the ipsilateral lung at this stage may also help in reducing LV volume overload. The lung connected to systemic circulation is also susceptible for recurrent infections.28 Pneumonectomy may be the only feasible option for a nonrecruitable ipsilateral lung with sequelae of irreversible pulmonary vascular disease or recurrent infections.34,37 However, pneumonectomy is not advisable as a single-stage procedure along with single-lung repair, as it increases the chance of RV failure and is best performed at a later stage.
Double-Lung Repair Ideal double-lung repair involves a complete anatomical and physiologic correction including VSD closure, relief of RVOT obstruction, and incorporating the ipsilateral lung into the pulmonary circulation. However, there are important prerequisites for such a repair. Candidates for double-lung repair should have: (1)
(2)
A well-developed ipsilateral hilar PA, which is present in type 2, 3, and 4 of this disease. In type 1, unifocalization of the ipsilateral lung is an option when there is sufficient development of the collaterals to allow unifocalization. Absence of irreversible pulmonary vascular disease in the ipsilateral side.
Severe pulmonary vascular disease has been reported as early as three months of age with anomalous origin of PA from the aorta.38 Assessment of pulmonary hypertension in the ipsilateral lung may require catheterization for pressure measurements (if there is proximal stenosis) and MRI to measure single-lung pulmonary blood flow. Stenosis of anomalous pulmonary vasculature may protect against the development of pulmonary vascular disease. (3)
Adequate sized PA anatomy after reconstruction: after connecting the ipsilateral lung to the main pulmonary
system, an assessment must be made regarding whether the PA system will have adequately low resistance to allow intracardiac repair and VSD closure. Objective assessment can be made using an intraoperative blood flow study.39 The MRI-based assessment looks promising for preoperative noninvasive assessment of PA system.17 Mean PA pressures of up to 25 to 30 mm Hg at full indexed cardiac output usually indicate the ability to move ahead with VSD closure. If the pressures are high, the patient should undergo a staged procedure with an initial repair with open or fenestrated VSD. Double-lung repair has been reported less frequently and mostly described in neonates with isolated UAPA.40-44 Murphy and associates45 have reported three cases of TOF with UAPA. One was a patient with TOF with absent pulmonary valve with absent LPA, which underwent a first stage 8-mm graft reconnection of affected LPA to RPA at three months of age. The second stage correction was done at 33 months, using a homograft conduit and 12-mm graft to LPA. The other two patients with TOF with UAPA underwent initial systemic shunt to affected LPA using 5-mm synthetic shunt at two months and six days of age, respectively, and underwent complete repair at 11 months and 20 months of age, respectively, with direct anastomosis of LPA to main pulmonary trunk. They were able to demonstrate that with an early recruitment, there is evidence of good growth of the affected PA with restoration of nearnormal perfusion to the left lung. Prifti et al has reported successful single-stage repair of a patient with TOF and anomalous origin of RPA from ascending aorta, at 18 days of age.46 Talwar and associates47 have reported two cases of TOF with UAPA with double aortic arch who underwent successful single-stage repair at 9 years and 12 years of age respectively. They used homograft saphenous vein in one case and homograft iliac artery in the second case for connecting the LPA to main PA. However, they have not commented about their assessment of the size of the reconstructed PA system and the stage of pulmonary vascular disease in the ipsilateral lung.
Palliative Operations Palliative operations are indicated for patients who are not suitable for the ideal complete two-lung repair or single-lung repair due to inadequate PA anatomy or LV size. They usually serve as the first-stage operation for patients requiring a staged approach to a complete repair or single-lung repair. Palliative procedures relieve cyanosis and polycythemia, prepare the contralateral lung for repair, and promote PA growth LV growth.18,20 Bockeria and associates18 have proposed the following classification system for palliative procedures in TOF with UAPA: Group 1: interventions that are aimed at increasing blood flow in the contralateral lung. These interventions include shunts between the systemic arterial tree and the ipsilateral PA or pulmonary trunk, reconstruction
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World Journal for Pediatric and Congenital Heart Surgery 5(1) of the RVOT without VSD closure, and transluminal balloon pulmonary valvuloplasty. Group 1 interventions are indicated in patients who are not suitable for single-lung repair due to inadequate PA anatomy or poor LV size. Bockeria et al18 reported 29 patients and 32 interventions from 1983 to 2011 with inhospital mortality rates of 7%. Of those patients, whose PA growth was adequate after initial palliation, 59% of the patients underwent a second-stage complete repair. They demonstrated that palliative reconstruction of RVOT provides more significant and uniform enlargement of the PA than systemic to pulmonary shunts or transluminal balloon pulmonary valvuloplasty. They suggested that systemic-to-PA shunt and transluminal balloon pulmonary valvuloplasty are methods of choice in patients with nonsevere hypoplasia of the contralateral PA. Balloon valvuloplasty is indicated more in patients with a prevailing valvular component of the pulmonary stenosis. Palliative reconstruction of the RVOT is a more favorable procedure for patients with a severe hypoplasia of the contralateral PA. Before this important series, the reported worldwide experience with similar palliative interventions is limited only to around 32 cases with an overall mortality of 22%. Most of the reports are isolated case reports with only very few centers having experience of 3 to 4 interventions.8,9,44,45 Group 2: interventions that are aimed to increase blood flow in ipsilateral lung or both lungs. They can be divided into group A and group B. (A)
(B)
Interventions that provide an increase in blood flow in the ipsilateral lung only include shunts between the subclavian artery and the hilar artery of the ipsilateral lung, creation of a communication between the pulmonary trunk and the hilar artery of ipsilateral lung, and any combination of these two procedures. Interventions that provide simultaneous increase in blood flow in both lungs. These interventions include placement of shunts between the systemic arterial tree and the contralateral PA in combination with a shunt between the systemic arterial tree and the hilar artery of ipsilateral lung, shunts between the subclavian artery and the contralateral PA in combination with creation of a communication between the pulmonary trunk and the hilar artery of ipsilateral lung, and creation of a communication between the pulmonary trunk and the hilar artery of ipsilateral lung in combination with palliative reconstruction of the RVOT.
Group 2 interventions are indicated in patients whose PA anatomy is inadequate for one-stage, double-lung repair. They help in promoting PA growth so that they can endure the complete cardiac output at the time of complete repair. Such palliations45 have been reported as a staged approach toward the ideal two-lung repair.
Nonintervention: Considering the high-perioperative mortality reported in many series,24,26 the surgeon may opt for no intervention at all. The anomalous circulation to the ipsilateral lung may provide freedom from cyanosis depending on the amount of pulmonary blood flow. The long-term problems are likely to be determined by progression of pulmonary hypertension in the ipsilateral lung and the degree of obstruction in the RVOT supplying the contralateral lung. Depending on these factors, consequences of UAPA may range from volume overload and congestive heart failure to progressive cyanosis. Some patients may be fortuitously well balanced. However, the natural history of this anomaly is not well elucidated. According to Williams et al,22 the untreated patients lead extremely restricted lives, and although the number of such patients with adequate follow-up is small, most die by 12 to 14 years. It is difficult to frame definite opinion about noninterventional management with the available data. Patients who present later in life with minimal cyanosis and mild symptoms may be candidate for nonintervention, especially those with nonreconstructable ipsilateral PA, with or without irreversible pulmonary vascular disease and a small sized contra lateral branch PA. It is reasonable to intervene in most other cases.
Timing of Repair The following factors demand consideration in determining the timing of repair: (1) Avoid development of pulmonary vascular disease and also loss of highly stenotic collaterals in the affected lung, (2) promote normal lung growth, (3) avoid long-term effects of cyanosis and RV hypertension, (4) risk of higher perioperative mortality while operating at a very young age, (5) unfavorable natural history (risk of dying during the waiting period), (6) institutional experience in managing small children, and (7) clinical status (cyanosis/overcirculation and failure). Surgical correction during early infancy is recommended in majority of type 1 and type 2 cases,48 with neonatal correction reserved for cases with hemodynamic instability (overcirculation/severe cyanosis), ductus supplying the disconnected pulmonary, or anomalous origin of a PA from aorta.46,48,49
Conclusion Tetralogy of Fallot with unilateral absence of PA can be surgically treated with acceptable morbidity and mortality, and adherence to strict selection criteria (Figure 5) is the key to success. Patients who present with a reconstructable ipsilateral PA and absence of irreversible pulmonary vascular disease in the ipsilateral lung should be considered for the double-lung repair. A single step or staged repair depends on the size and resistance of the PA system after reconstruction. Those with nonreconstructable ipsilateral PA and those who present late with irreversible pulmonary
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Figure 5. Flowchart for management of TOF with UAPA. TOF indicates tetralogy of Fallot; UAPA, unilateral absence of pulmonary artery.
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World Journal for Pediatric and Congenital Heart Surgery 5(1)
vascular disease should be planned for single-lung repair. An adequate sized contralateral PA and LV is a prerequisite for singlestage repair. Patients with small contralateral PA or LV should be offered an initial palliative procedure, followed by periodic reassessment of PA and LV size. Those with adequate growth of PA or LV may become candidates for single-lung correction. The option of nonintervention should be individualized based on the clinical presentation and feasibility for repair. Long-term follow-up studies with larger groups of patients are needed to refine treatment options for patients with TOF with UAPA. Acknowledgments
11.
12.
13.
14.
The authors thank Dr Adil Sadiq, consultant cardiac surgeon, Apollo Hospitals, Bangalore, for his illustrations. 15.
Declaration of Conflicting Interests The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
16.
Funding The author(s) received no financial support for the research, authorship, and/or publication of this article.
17.
Notes Note 1: branch PA refers to LPA or RPA. Note 2: ipsilateral refers to the side in which branch PA is disconnected or absent, and contralateral refers to the normal side. 18.
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