Surgical Treatment of Absent Pulmonary Valve Syndrome Associated ...

PEDIATRIC CARDIAC SURGERY:

Surgical Treatment of Absent Pulmonary Valve Syndrome Associated With Bronchial Obstruction John W. Brown, MD, Mark Ruzmetov, MD, PhD, Palaniswamy Vijay, MPH, PhD, Mark D. Rodefeld, MD, and Mark W. Turrentine, MD Section of Cardiothoracic Surgery, Indiana University School of Medicine, and James Whitcomb Riley Hospital for Children, Indianapolis, Indiana

Background. Absent pulmonary valve syndrome (APVS) is a relatively rare anomaly that is usually associated with a ventricular septal defect and a restrictive pulmonary annulus with severe pulmonary regurgitation. The to-and-fro flow across the right ventricular outflow tract produces enormously dilated and pulsatile pulmonary arteries (PAs) that cause severe respiratory distress and tracheomalacia by compression of the trachea and primary bronchi. This retrospective study summarizes our 20-year experience of surgical treatment in patients with APVS. Methods. Between 1984 and 2005, 20 patients underwent repair of APVS using a valved conduit (n ⴝ 9), transannular patch (TAP) insertion alone (n ⴝ 5), or TAP with monocusp valve (n ⴝ 6) with PA reduction arterioplasty. Median age was 7 months (range, 6 days to 9 years). Results. There were one perioperative and two late deaths. All deaths were related to airway complications. Survival was 90% at 1 year and 85% at 10 and 15 years. In a multivariate analysis only preoperative ventilator de-

pendency was associated with a worse outcome (p ⴝ 0.02). Follow-up was available in 18 operative survivors (mean follow-up, 7.3 ⴞ 5.2 years). Six patients (33%) underwent reoperation for pulmonary valve incompetence and right ventricular dysfunction. Three patients (17%) had episodic bronchospasm of mild to moderate severity that were responsive to sympathomimetic bronchodilators. Conclusions. Morbidity associated with perioperative respiratory complications and ventilator dependency due to underlying tracheobronchomalacia is an important problem in patients with APVS. These infants may require multiple hospitalizations for recurrent respiratory infections secondary to their tracheobronchomalacia. Complete repair with a valved conduit and reduction pulmonary arterioplasty at the onset of symptoms and a definitive diagnosis is our procedure of choice for infants with APVS. With this approach, the airway can be optimized to give the best patient outcome. (Ann Thorac Surg 2006;82:2221– 6) © 2006 by The Society of Thoracic Surgeons

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be inserted or how the size of the PA should be reduced [3– 6]. Mortality for surgical repair in these patients is increased, especially in infants presenting with severe respiratory compromise [3, 5, 6]. Previous reports have shown improved early outcome when plication of the dilated pulmonary arteries is performed to relieve airway obstruction [3, 5, 6]. Persistent respiratory symptoms and the need for reoperation years later to replace a dysfunctional pulmonary valve are problems associated with this patient population. The purpose of this study is to report our surgical experience, since 1984, with a consecutive series of patients with absent pulmonary valve syndrome.

bsent pulmonary valve syndrome (APVS) is a rare malformation in which the pulmonary valve is absent or rudimentary. Rarely isolated, it is associated in most cases with a malalignment type of ventricular septal defect (VSD), right ventricular hypertrophy, or stenotic pulmonary annulus and is therefore classified as a variant of tetralogy of Fallot (TOF). The characteristic feature of this syndrome is aneurysmal pulmonary arteries (PAs) leading to obstruction of the bronchial tree with severe respiratory distress, especially in the neonatal period [1–3]. Operative treatment remains a controversial subject. There is no consensus whether a pulmonary valve should

Accepted for publication July 11, 2006. Presented at the Poster Session of the Forty-second Annual Meeting of The Society of Thoracic Surgeons, Chicago, IL, Jan 30 –Feb 1, 2006.

Material and Methods

Address correspondence to Dr Brown, Section of Cardiothoracic Surgery, Indiana University School of Medicine, 545 Barnhill Dr., EH 215, Indianapolis, IN 46202-5123; e-mail: [email protected].

Between January 1984 and October 2005, 20 patients were operated on for TOF with APVS at the Riley Children’s Hospital in Indianapolis, Indiana (Fig 1). Median age was

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BROWN ET AL ABSENT PULMONARY VALVE SYNDROME REPAIR

CARDIOVASCULAR Fig 1. Distribution and disposition of patients with tetralogy of Fallot with absent pulmonary valve syndrome who underwent various surgical repairs. (APVS ⫽ absent pulmonary valve syndrome; RV-PA ⫽ right ventricular to pulmonary artery; PTFE ⫽ polytetrafluoroethylene.)

7 months (range, 6 days to 9 years; mean, 28 ⫾ 33 months) and median weight was 6.6 kg (range, 2.4 to 38 kg; mean, 11 ⫾ 9.3 kg). There were 10 girls and 10 boys. A review of each patient’s complete medical record was performed. Follow-up data were obtained from the medical records and through correspondence from the patients’ cardiologists. This study has been approved and the Indiana University Institutional Review Board waived the need to obtain patient consent for this study. A large spectrum in the severity of symptoms was observed among patients. Patients could be classified into two groups according to their age at operation and time of surgery. The infant group consisted of 11 patients less than 1 year of age. All infants were operated on after 1993 and were markedly symptomatic with severe respiratory distress, episodes of respiratory obstruction, and bronchopulmonary infection requiring repeated hospital admissions. Eight required mechanical ventilation preoperatively. Older children (more than 1 year old; n ⫽ 9) had milder respiratory or cardiac symptoms but significant bronchial obstruction which was confirmed by bronchoscopy preoperatively in five of them. Clinical findings in both groups included a pansystolic murmur and low-pitched diastolic murmur at the left sternal border, varying degrees of cyanosis, and tachyFig 2. (A) Line of resection of main pulmonary artery and anterior portion of main branches. Pulmonary artery is transected at annulus and incision is made into the right ventricular outflow tract. (B) Arterioplasty of right and left pulmonary artery branches reduces their caliber. (C) Completed repair using bovine jugular vein conduit.

Ann Thorac Surg 2006;82:2221– 6

pnea. Second pulmonary sound P2 was absent. Chest X-ray showed cardiomegaly and gross dilatation of the main, left, and right pulmonary arteries in all patients. Pulmonary vascularity was normal or slightly reduced. All infants and children underwent two-dimensional echocardiography and Doppler assessment and 10 had a cardiac catheterization and angiography. Associated intracardiac malformations were present in 10 of the 20 patients (50%), including ostium secundum type of atrial septal defect (n ⫽ 8), patent ductus arteriosus (n ⫽ 1), left superior vena cava (n ⫽ 1), absent left pulmonary artery (n ⫽ 1), single coronary artery of the left descending coronary artery crossing the RVOT (n ⫽ 1), and multiple aortopulmonary collaterals (n ⫽ 1). Four patients had extracardiac anomalies including DiGeorge syndrome (n ⫽ 1), Goldenhar syndrome (n ⫽ 1), CHARGE syndrome (a syndrome of associated defects, including coloboma of the eye, heart anomaly, choanal atresia, retardation, and genital and ear anomalies) (n ⫽ 1), and VATER syndrome (vascular anomalies, anal atresia, tracheoesophageal fistula, esophageal atresia, and renal anomalies) (n ⫽ 1).

Operative Technique Operative repair was performed through a median sternotomy with aortobicaval cannulation, continuous cardiopulmonary bypass, hypothermia at 26°C to 28°C, and intermittent dose cold blood potassium cardioplegia. Extracorporeal circulation time ranged from 112 to 198 minutes (mean, 151 ⫾ 27 minutes) and aortic cross-clamping time ranged from 31 to 123 minutes (mean, 74 ⫾ 29 minutes). The right atrium was opened and patent foramen ovale or atrial septal defect was closed by patch or direct suture. In 2 infants a small atrial septal defect was left open. This was done in anticipation of high right-sided pressures postoperatively. A vertical infundibulotomy was then performed and the intracardiac anatomy was defined (Fig 2). Right ventricular outflow tract (RVOT) relief was achieved by resection of the hypertrophied infundibular muscle bands. The VSD was then closed using an elastic Dacron (C.R. Bard, Haverhill, PA) patch (n ⫽ 11) or Gore-Tex (W.L. Gore & Assoc, Flagstaff, AZ) patch (n ⫽ 9) anchored with interrupted pledgeted sutures. Ventricular septal defect closure was done through the right ventriculotomy in all cases.


Table 1. Type of RVOT and PA Reconstruction in Children With Absent Pulmonary Valve Syndrome Reconstruction or Reduction Type of RVOT reconstruction Conduit PTFE monocusp Transannular patch Type of PA reduction Anterior reduction of MPA, RPA, and LPA Anterior reduction only MPA Anterior reduction and posterior plication of MPA, RPA, and LPA

Number of Patients 9 6 5 14 5 1

LPA ⫽ left pulmonary artery; MPA ⫽ main pulmonary artery; PA ⫽ pulmonary artery; PTFE ⫽ polytetrafluoroethylene; RPA ⫽ right pulmonary artery; RVOT ⫽ right ventricular outflow tract.

Reduction pulmonary arterioplasty was performed in all patients (Table 1). An anterior arterioplasty was limited to the main pulmonary artery (n ⫽ 5) and the main, right, and left PAs (n ⫽ 14), and anterior reduction and posterior plication of the main, right, and left PAs with pulmonary arterioplasty was performed in one. The posterior wall of the PAs and their attachment to the bronchi were left undisturbed. The RVOT reconstruction, including the arterioplasty, was performed with the cross-clamp off and the heart beating in most cases. The RVOT was reconstructed with a transannular patch alone in 5 patients (all before 1993). A transannular patch was performed with Gore-Tex (W.L. Gore & Assoc) in 4 patients and with autologous pericardium in one patient. A polytetrafluoroethylene (PTFE) monocusp patch was inserted in 6 children beginning in 1993 (Table 1). In the remaining 9 patients, reconstruction included RV-PA conduit, a cryopreserved valved pulmonary homograft (CryoLife Inc, Kennesaw, GA; n ⫽ 6), jugular vein valved Contegra conduit (Medtronic Inc, Minneapolis, MN; n ⫽ 2), and nonvalved Hemashield graft (Meadox Medical Inc, Oakland, NJ; n ⫽ 1). The size of conduit varied from 10 to 26 mm (mean, 14.6 ⫾ 4.7 mm). A conduit was first anastomosed distally to the PA bifurcation and then proximally to the RVOT using a running polypropylene suture. Most of the surgeries in infants were done on an urgent basis. The proximal conduit reconstruction was performed with a Gore-Tex hood. Intraoperative transesophageal echocardiography was done in the last 11 patients to assess adequacy of repair; it was not available for the first 9 patients. In one patient, the left PA was discontinuous with the main PA and supplied by a patent ductus arteriosus. Reimplantation of the left PA to the pulmonary trunk and patent ductus arteriosus ligation were performed. In 2 patients (before 1990), correction of the APVS was performed as a two-stage repair. The first stage procedure was palliative and was described by Litvin and colleagues [7]. The right PA was divided at its origin from the main PA and brought anterior to the ascending aorta. It was reattached to the main PA with a short interposi-

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tion 10 mm Dacron graft. At a second stage (3 and 7 years after initial surgery), correction of the APVS was accomplished using a large (16 mm) Dacron graft.

Statistical Analysis The SPSS statistical program for Windows version 10 (SPSS, Inc, Chicago, IL) was used to perform the data analysis. Data are expressed as mean, median, and range. Actuarial estimates of freedom from postoperative events were accomplished with Kaplan-Meier methods and p values for differences between distributions were obtained by log-rank testing. Factors evaluated in multivariate analysis for risk of mortality and reoperation included age, weight, sex, date of operation, cardiopulmonary bypass and aortic cross-clamping time, preoperative ventilator dependency, preoperative severe respiratory distress, associated cardiac or noncardiac syndromes, previous cardiac operations, concomitant cardiac operations, type of PA reduction, type of RVOT reconstruction, and size of conduit. The analyses were performed with Cox proportional hazards regression. A forward step-wise selection method was used to add variables to the model requiring significance at p less than 0.10 for entry and p less than 0.05 for retention. Early death is defined as death in the hospital or death within 30 days after the procedure. All other deaths are considered late.

Results Survival There was one perioperative and two late deaths. One patient died early despite extracorporeal membrane oxygenation support for low cardiac output. Both late deaths were related to airway complications. The first late death occurred two months after initial surgery due to aspiration and pneumonia. The second late death occurred in a child three months after initial surgery due to bronchopneumonia and sepsis. All three had required preoperative mechanical ventilation and were infants less than 40 days of age at the time of surgery. Overall survival was 90% at 1 year and 85% at 5 and 10 years. Overall mortality was associated with a longer aortic cross-clamp time (p ⫽ 0.002), younger age at operation (p ⫽ 0.001), and preoperative ventilator dependency (p ⬍ 0.001). In a multivariable analysis, only preoperative ventilator dependency was associated with a worse outcome (p ⫽ 0.02). The duration of mechanical ventilation after repair varied from 1 to 34 days (mean, 6 ⫾ 7 days) and the intensive care unit stay varied from 4 to 52 days (mean, 8 ⫾ 13 days). The postoperative course was completely uneventful in 16 children (7 infants and 9 older children). Recovery from respiratory distress was delayed in 2. One infant required plication of the left diaphragm and one had pneumonia requiring mechanical ventilation for 34 days. Surgical treatment has been offered at an earlier age in patients since 1993 compared with a group of patients prior to 1993 (p ⫽ 0.001). Infants were more likely

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Overall freedom from RVOT reoperation estimated by the Kaplan-Meier method was 83% at 5 years and 66% at 10 and 15 years. Univariate and multivariate analysis showed the presence of a PTFE monocusp patch (p ⫽ 0.04) and cryopreserved pulmonary homograft insertion (p ⫽ 0.001) as the best predictor for the need for RVOT reoperation.

Comment

Fig 3. Freedom for reoperation in patients with absent pulmonary valve syndrome estimated by the Kaplan-Meier method. (⽧ ⫽ overall; ⫽ right ventricle to pulmonary artery conduit; Œ ⫽ polytetrafluoroethylene; ⫽ transannular patch.)

to be intubated preoperatively (p ⬍ 0.001). Patients were more likely to undergo branch anterior pulmonary artery arterioplasty after 1993 (82%) than before 1993 (p ⫽ 0.02).

Follow-Up Nineteen patients, including 10 infants survived the initial surgical procedure. Follow-up was available on 18 of 19 survivors. One patient (first in our series, who underwent initial surgery in 1984) was lost at follow-up nine years after surgery. The follow-up interval ranged from 3 months to 15 years (mean, 7.3 ⫾ 5.2 years). All surviving patients are currently well without physical limitations. Of the 16 late surviving patients, New York Heart Association (NYHA) functional class was markedly improved with 14 patients in class I, and 2 in class II. All patients are in normal sinus rhythm and 2 have right bundle branch block. Persistent respiratory symptoms including reactive airway disease with respiratory tract infection requiring at least periodic medication (bronchodilators) was noted in three survivors, all of whom underwent surgery as infants. Symptoms have tended to lessen with time. No patients require assisted ventilation or were discharged with a tracheostomy. No patients underwent reoperation for worsening respiratory symptoms.

Reoperation Six of 18 patients (33%) have required reoperations during the follow-up period (Fig 3). The mean interval between initial procedure and reoperation was 5.5 ⫾ 2.7 years (range, 2 to 9 years). The indications for the reoperation was RV-PA conduit insufficiency or stenosis (n ⫽ 4), and PTFE monocusp insufficiency (n ⫽ 2). The systolic RV-PA conduit gradient ranged from 35 to 80 (mean, 57 ⫾ 22 mm Hg). Two patients with PTFE monocusp patch and 2 patients with cryopreserved pulmonary homograft underwent reoperation with the Contegra conduit (n ⫽ 4). Another two patients with cryopreserved pulmonary homograft underwent PTFE monocusp patch enlargement. The time interval between patients with PTFE monocusp patch and pulmonary homograft conduit insertion was significantly different (8.5 ⫾ 0.7 years versus 4 ⫾ 1.8 years; p ⫽ 0.03).

Tetralogy of Fallot with an absent or rudimentary pulmonary valve is a rare congenital cardiac malformation comprising 3% to 5% of all cases of the tetralogy complex. In 1847, Chevers was the first to describe this syndrome [8], which included a large VSD and stenosis at the PA annulus with or without narrowing of the right ventricular infundibulum, and two additional unique features, pulmonary regurgitation secondary to an absent or rudimentary pulmonary valve and aneurysmal dilatation of the pulmonary trunk and the main pulmonary arterial branches. The pathogenesis of this syndrome is still controversial as the structural microscopic findings of the pulmonary artery wall are variable according to different studies [3, 4, 9]. Embryologic studies implicate an absent ductus arteriosus causing fetal pulmonary regurgitation that leads to massively dilated PAs and tracheobronchial compression [3, 10]. In 1990, Momma and colleagues [11] created an experimental model of tetralogy of Fallot with an absent pulmonary valve in rats treated by bisdiamine, a teratogen interfering with neural crest cells. These authors found that enlargement of the PAs was already present in utero and was correlated with a lesser degree of pulmonary annulus stenosis. Moreover, they noticed compression and deformity of the bronchial tree already during fetal life. Patients with this syndrome can be divided into two groups depending on age and severity of symptoms. The first group comprises infants with severe cardiorespiratory distress. The results of medical and surgical treatment in this group have generally been poor. Many die of a combination of intractable heart failure and airway obstruction resulting from compression of the bronchi by massively dilated pulmonary arteries. Medical treatment often fails to control the symptoms and the various surgical procedures have had a high mortality. In severely ill infants, obtaining respiratory stability is the first priority. Postural drainage, air humidification, nebulizer therapy, and intubation with mechanical ventilation with high positive end-expiratory pressure (10 cm H2O) are initiated as required. The second group includes older patients with mild symptoms who survive infancy. In these patients, closure of the VSD and relief of pulmonary stenosis can be performed later on an elective basis with low risk. In infants with TOF and APVS who present with severe respiratory problems, a number of palliative and reparative operations were introduced during the 1960s and 1970s. Palliative procedures included tacking-up the PAs or the aorta to the sternum, transecting the right pulmo-



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Study Snir (1991) [9] Watterson (1992) [6] Godart (1996) [3] McDonnell (1999) [5] Dodge-Khatami (1999) [4] Hew (2002) [19] Brown (2006) [24]

No. of Patients Total/Infants

Infant Mortality

Mean Follow-up (Year)

Late Death

Reoperation

Respiratory Complication

22/8 19/18 37/10 28/18 11/10 54/39 20/11

25% 17% 20% 33% 10% 21% 9%

3.6 N/A 3 5.5 2.1 6.4 7.3

1 1 1 1 1 5 2

0 5 1 3 5 15 6

2 3 N/A 4 2 N/A 3

nary artery and reattaching it to the pulmonary trunk in front of the aorta [7], creation of a classic Glenn shunt [12], reducing the size of the PAs [2, 13], lobectomies of collapsed or emphysematous lungs [1], and ligation or banding of the pulmonary trunk with construction of a central shunt [1, 14, 15]. For many years, ligation or banding of the pulmonary artery with construction of systemic-to-pulmonary artery shunt was the procedure of choice in these ill infants [16, 17]. We used Litvin’s palliative method in our two patients. Complete correction before the 1980s was mostly reserved for older less symptomatic children. Recently a more aggressive approach focusing on complete repair of these severely ill neonates and infants has yielded improved results and these are shown in Table 2 [3– 6, 9, 18, 19, 24]. We agree with most authors that reduction PA arterioplasty is needed in most patients. However, there is no general consensus whether a pulmonary valve, or a valved or nonvalved conduit, should be inserted and the degree of size deduction of PAs. McCaughan and colleagues [20] recommended insertion of a pulmonary valve and plication of aneurysmal PAs in infants with APVS. In older children, they believe both these steps are not necessary. Ilbawi and colleagues [17] recommended pulmonary valve insertion in the older patients group, and for infants they prefer palliation first. Insertion of a valved conduit was also recommended by Snir and colleagues [9] and Dodge-Khatami and colleagues [4], whereas others [3, 18] place more emphasis on reduction of pulmonary artery size by anterior resection and posterior plication. We have always treated patients with APVS by closing the ventricular septal defect; however, our approach to the pulmonary valve varied over time. Before 1992, the children tended to be older at time of surgery; since 1993, 11 of 13 patients have undergone surgery as neonates and infants. Before 1990, pulmonary valve implantation was not done and the RVOT was reconstructed with a transannular patch in all patients. Since 1991, all patients have undergone combined anterior PA reduction and insertion of either a valved conduit or PTFE monocusp outflow tract patch. Since 2000, we have used a fairly uniform technique consisting of VSD closure, placement of a right ventricle to pulmonary artery conduit (usually Contegra), and reduction of the size of the PAs. One patient had the addition of a posterior wall plication as suggested by Stellin and colleagues [18].

Despite advances in surgical techniques for repair of the cardiac lesions in TOF and APVS, survival remains less than ideal in many instances due to respiratory compromise from tracheobronchomalacia. The standard medical therapy for this has been positive pressure ventilation with or without a tracheostomy. There were few other techniques to relieve respiratory symptoms of the APVS: placement of bilateral Palmaz bronchial stents [21, 22], external stabilization using ring-reinforced PTFE prostheses [23], or balloon expandable metallic stents [4]. We have not used endobronchial stents as a treatment option in this setting. Tetralogy of Fallot with APVS is a well-recognized distinct clinical entity that may present early in life as a surgical emergency. Morbidity associated with postoperative respiratory complications and ventilatordependency due to underlying tracheobronchomalacia is an important problem in patients with APVS. These infants may require multiple postoperative hospitalizations for recurrent respiratory infections secondary to their tracheobronchomalacia. Complete repair with a valved conduit and reduction pulmonary arterioplasty in infancy at the time of symptom onset is the procedure of choice for infants with APVS. With this approach the patient outcome is determined by the status and management of their airway. Long-term follow-up is necessary for this subgroup.

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Table 2. Recent Reports of Tetralogy of Fallot With Absent Pulmonary Valve Syndrome

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7. Litvin SB, Rosenthal A, Fellows K. Surgical management of young infants with tetralogy of Fallot, absence of the pulmonary valve, and respiratory distress. J Thorac Cardiovasc Surg 1973;65:552– 8. 8. Chevers N. Recherches sur les maladies de l’artere pulmonaire. Arch Gen Med 1847;15:488 –508. 9. Snir E, de Leval MR, Elliott MJ, et al. Current surgical technique to repair Fallot’s tetralogy with absent pulmonary valve syndrome. Ann Thorac Surg 1991;51:979 – 82. 10. Fouron JC, Sahn DJ, Bender R, et al. Fetal cardiac morphology of tetralogy of Fallot with absent pulmonary valve. Am J Cardiol 1989;64:547–9. 11. Momma K, Ando M, Takao A. Fetal cardiac morphology of tetralogy of Fallot with absent pulmonary valve in the rat. Circulation 1990;82:1343–51. 12. Waldhausen JA, Friedman S, Nicodemus H, Miller W, Rashkind W, Johnson J. Absence of the pulmonary valve in patients with tetralogy of Fallot: surgical management. J Thorac Cardiovasc Surg 1969;57:669 –74. 13. Bove EL, Shaher RM, Alley RM, McKneally M. Tetralogy of Fallot with absent pulmonary valve and aneurysm of the pulmonary artery: report of two cases presenting as obstructive lung disease. J Pediatr 1972;81:339 – 43. 14. Opie JC, Sandor GG, Ashmore PG, Patterson MW. Successful palliation by pulmonary artery banding in absent pulmonary valve syndrome with aneurismal pulmonary arteries. J Thorac Cardiovasc Surg 1983;85:125– 8. 15. Park MK, Trinkle JK. Absent pulmonary valve syndrome: a two-stage operation. Ann Thorac Surg 1986;41;669 –71. 16. Byrne JP, Hawkins JA, Battiste CE, Khoury GH. Palliative procedures in tetralogy of Fallot with absent pulmonary valve: a new approach. Ann Thorac Surg 1982;33:499 –502.


17. Ilbawi MN, Fedorchik J, Muster A, et al. Surgical approach to severely symptomatic newborn infants with tetralogy of Fallot and absent pulmonary valve. J Thorac Cardiovasc Surg 1986;91:584 –9. 18. Stellin G, Jonas RA, Goh TH, Brawn WJ, Venables AW, Mee RB. Surgical treatment of absent pulmonary valve syndrome in infants: relief of bronchial obstruction. Ann Thorac Surg 1983;36:468 –75. 19. Hew CC, Daebritz SH, Zurakowski D, del Nido PI, Mayer JE, Jonas RA. Valved homograft replacement of aneurismal pulmonary arteries for severely symptomatic absent pulmonary valve syndrome. Ann Thorac Surg 2002;73: 1778 – 85. 20. McCaughan BC, Danielson GK, Driscoll DJ, McGoon DC. Tetralogy of Fallot with absent pulmonary valve: early and late results of surgical treatment. J Thorac Cardiovasc Surg 1985;84:280 –7. 21. Filler RM, Forte V, Fraga JC, Matute J. The use of expandable metallic airway stents for tracheobronchial obstruction in children. J Pediatr Surg 1995;30:1050 – 6. 22. Subramanian V, Ansted M, Cottrill CM, Kanga J, Gurley J. Tetralogy of Fallot with absent pulmonary valve and bronchial compression: treatment with endobronchial stents. Pediatr Cardiol 1997;18:237–9. 23. Hagl S, Jakob H, Sebening C, et al. External stabilization of long-term tracheobronchomalacia guided by intraoperative bronchoscopy. Ann Thorac Surg 1997;64:1412–21. 24. Brown JW, Ruzmetov M, Vijay P, Rodefeld MD, Turrentine MW. Surgical treatment of absent pulmonary valve syndrome associated with bronchial obstruction. Ann Thorac Surg 2006;82:2221– 6.