Palliation of Truncus Arteriosus Associated With Complete Atrioventricular Canal—Results of Single Ventricle Palliation

Introduction

Truncus arteriosus (TA) associated with complete atrioventricular canal defect (CAVC) is a rare and challenging complex malformation involving both atrioventricular and ventriculoarterial junctions. So far 23 patients have been reported in the English literature, ^{1 –3} with five managed surgically (biventricular repairs in three patients ^{4 –6} and single ventricular palliation in two patients ⁷ ). In the absence of anterior/outlet extension of the inlet ventricular septal defect (VSD) associated with CAVC (remote VSD), biventricular repair involves a number of challenges so that single ventricle palliation pathway may be the preferred management option. We report our experience with five such patients.

Patients and Methods

All patients diagnosed with TA-CAVC who received single ventricular palliation at a single center from July 2007 to April 2014 were reviewed retrospectively. Demographic, echocardiographic and cardiac catheterization data, and medical records were reviewed. A waiver of documentation of informed consent was approved by Children’s National Health System Institutional Review Board.

Results

A total of five patients underwent single ventricle palliation for TA-CAVC during the study period. The demographic, clinical, and anatomical details of the patients are summarized in Table 1. One patient was premature (<36 weeks), and all five patients had chromosomal abnormalities (DiGeorge syndrome in four patients and Down syndrome in one patient). The mean birth weight was 2.80 ± 0.45 kg. There were two stage I operative mortalities (one from sepsis and multiorgan failure and a second from renal failure). The remaining three patients underwent stage II in the form of superior cavopulmonary connection and takedown of shunt/conduit. At a median follow-up of 210 days (interquartile range 1,210 days), one patient is interstage II to III, and two successfully completed stage III Fontan palliation.

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Table 1.

Demographic, Anatomical, and Clinical Details.

Case	1	2	3	4	5
Age at stage I, days	8	10	5	21	3
Body weight, kg	2.6	3.0	2.5	3.5	2.4
Gender	Female	Male	Male	Female	Female
Chromosomal abnormality	DiGeorge	DiGeorge	DiGeorge	DiGeorge	Down
Associated defects	TA + CAVC Rastelli C + RAA + LSVC	TA + unbalanced CAVC (hypo left) + RAA + LSVC	TA + CAVC Rastelli C + LAA + OSASD + dextrocardia	TA + unbalanced CAVC (hypo left) + RAA + OSASD	TA + CAVC Rastelli C + LAA + OSASD + PDA
TA type	1.5	2	3	2	2
PA branch	Confluent	Confluent	Discontinuous (RPA arising from RCAA)	Confluent, hypo LPA	Confluent
Stage I details	Excision of PAs, RV-PA conduit	Bilateral branch, PAB	Excision of PAs, PA unifocalization, systemic to PA shunt	Excision of PAs, systemic to PA shunt	Excision PAs, RV-PA conduit, PDA closure
Ventricular size	Balanced	Unbalanced, hypoplastic LV	Balanced	Unbalanced, hypoplastic LV	Balanced
Truncal valve function; morphology	Mild regurgitation; quadricuspid	No regurgitation; tricuspid	Trivial regurgitation; tricuspid	Mild stenosis and regurgitation; quadricuspid	No regurgitation; tricuspid
VSD component	Large inlet VSD, no outlet extension, multiple atrioventricular valve attachments precluding baffle placement	Large AVC type VSD, extending on to conal septum	Large inlet VSD, no outlet extension, multiple atrioventricular valve attachments precluding baffle placement	Large inlet VSD extending to posterior muscular septum	Large inlet VSD, no outlet extension, multiple atrioventricular valve attachments precluding baffle placement
Follow-up length, days	1,860	1,290	210	33	80
Status	Alive, completed stage III	Alive, completed stage III	Alive, interstage II-III	Stage I mortality	Stage I mortality

Abbreviations: CAVC, complete atrioventricular defect; kg, kilogram; LAA, left aortic arch; LPA, left pulmonary artery; LSVC, left superior vena cava; OSASD, ostium secundum atrial septal defect; PA, pulmonary artery; PAB, pulmonary artery band; PDA, patent ductus arteriosus; RAA, right aortic arch; RCAA, right carotid artery; RPA, right pulmonary artery; RV, right ventricle; TA, truncus arteriosus.

There were two mortalities after neonatal palliative procedures. The first mortality (case 4 in the series) underwent neonatal pulmonary artery excision and placement of a systemic to pulmonary artery shunt using a 3.5-mm Gore-Tex tube graft. After an uneventful intraoperative and early postoperative course, she underwent delayed sternal closure on postoperative day 3 and was extubated on postoperative day 6. However, during the second postoperative week, she had hemodynamic decompensation due to congestive heart failure, which led to cardiac arrest and need for extracorporeal membrane oxygenation (ECMO) support. This acute event led to significant renal insult to her already compromised renal function (ectopic right kidney and cystic left kidney). Although she was weaned and decannulated off ECMO after two weeks, she continued to require renal replacement therapy, which led to her eventual demise on postoperative day 33. The second death (case 5 in the series) was a patient who was taken to the operating room for a biventricular repair. Intraoperatively, however, his VSD was noted to be unroutable to the outlet, as it was limited to the inlet septum, with multiple atrioventricular valvar tissue attachments in the baffle pathway. He therefore underwent excision of pulmonary arteries and a right ventricle to pulmonary artery conduit placement. His initial postoperative course was rocky, with a need for high inotropic support, which later stabilized to allow staged delayed sternal closure (partial closure on postoperative day 6 and complete closure on day 13). His postoperative echocardiograms were remarkable for right ventricular dysfunction, tricuspid regurgitation, and conduit gradients of 50 to 70 mm Hg in a clinical setting of balanced systemic to pulmonary blood flow. A hemodynamic cardiac catheterization was planned, however the patient developed significant chylous effusions, multiorgan failure, sepsis, and died on postoperative day 80.

Discussion

Truncus arteriosus associated with CAVC poses significant surgical challenge for a biventricular repair, ^7,9 except in a few anatomical subsets with extension of the VSD to the outlet septum. In the absence of outlet extension of the inlet defect, biventricular repair is complicated by the need for a long complex baffle with risk to atrioventricular valve function and left ventricular outflow tract obstruction in addition to mandatory conduit changes.

A challenging neonatal palliative procedure is required to start these patients along the single ventricle palliation pathway. The operation needs to be tailored to the individual patient’s anatomy and may involve excision of the pulmonary arteries, unifocalization of the branches, along with an additional source of pulmonary blood flow. In favorable cases, placement of bilateral branch pulmonary artery bands may be an option.

To our knowledge, this is the first reported series of patients with combination of TA-CAVC followed through the entire three-stage single ventricle palliation pathway. While the observed mortality for neonatal palliation in this series (40% [2 of 5]) is high compared to other single ventricle cohorts, there were multiple additional risk factors other than the complex anomaly itself, including extracardiac/chromosomal anomalies (100% of patients) and low birth weight (Table 1). Of the two mortalities, one patient had DiGeorge syndrome and died from complications of renal failure, while the other with Down syndrome and birth weight of 2.4 kg in this series died of refractory sepsis on postoperative day 80.

Biventricular repairs may be possible in a subset of patients with this complex anatomy. This would require extension of the VSD to the outlet septum and long complex baffles which may be more prone to recurrent left ventricular outflow tract obstruction. Other considerations include potential need for multiple conduit changes and reintervention for truncal valve regurgitation. These challenges, however, must be carefully weighed against the drawbacks of single ventricle physiology.

All neonatal survivors however so far have had uneventful subsequent courses, suggesting normalization of risk after neonatal palliation in these patients.

Conclusion

Combination of TA with complete CAVC is a rare combination of defects, which pose significant challenges to surgical repair. In the absence of outlet extension of the VSD, single ventricle palliation can be successfully employed. The surgical plan needs to be tailored to the individual patient’s anatomy.