Right Ventricle to Pulmonary Artery Conduit as Palliative Procedure in Ductus Arteriosus Circulation-Dependent Infant

Introduction
Blalock-Taussig shunt (BTS) is the historical palliative surgical option in infants with ductus arteriosus (PDA) circulation-dependent or severely symptomatic Tetralogy of Fallot (TOF) that are not amenable to primary repair (1). Herein, the authors present right ventricle to pulmonary artery conduit (RVPAC) as an alternative surgical palliation technique in a medically complex infant with double outlet right ventricle.

Case Video
This is a term female newborn with a birth weight of 2.73 kg and diagnosis of VACTERL association, pulmonary atresia, ventricular septal defect (VSD), and malposed great vessels, who was a non-candidate for early complete repair. She was initially palliated with a 3.5x12 mm PDA stent at 6 days of age. Postoperative course after neonatal trachea-esophageal fistula repair was complicated by recurrent desaturations and failure to progress with feeds due to cardiorespiratory distress. Computed tomography showed origin muscular stenosis of bilateral pulmonary arteries (PA), with negligible flow in the left PA. The patient was electively taken to the operating room at 4 months of age for surgical palliation. Cardiopulmonary bypass with bicaval cannulation was initiated and the PDA was ligated. Distal PAs were controlled with Yasargil Clips and the main PA was incised. Protruding PDA stent and thickened tissues were excised from the PAs, followed by bilateral reconstruction using autologous pericardium. Next, the heart was arrested with anterograde cardioplegia. A 6 mm Gore-Tex RVPAC was anastomosed from the right infundibular ventriculotomy site to the central PA with double-layer sutures at the proximal anastomosis. Post-repair SpO2 was 88%.

The postoperative course was complicated with a brief episode of necrotizing enterocolitis and discharged postoperative day 21. At the time of Rastelli repair at 11 months of age, the patient was 8.9 kg and bilateral PA patency was reasonable. SpO2 remained in the mid-80s with no evidence of volume overloading.

Discussion
RVPAC provides satisfactory hemodynamic adaptation in infants with biventricular heart disease and inadequate pulmonary circulation, achieving survival outcomes comparable to BTS or single stage complete repair (2). Zheng et al. reported no significant difference in in-hospital mortality, mechanical ventilation time, pediatric intensive care unit stay, and hospital stay between RVPAC and system-to-PA shunts (S-PA, p > 0.05) (3). In fact, RVPAC was associated with superior PA growth (p < 0.001) and a higher rate of second-stage biventricular surgery (p = 0.03) compared to S-PA (3). Modified BTS has been shown to promote significant absolute growth of the pulmonary valve, main PA, and bilateral PAs in neonates with TOF and speculated to facilitate valve-sparing repair in one-third of patients with pulmonary atresia (1). Comparatively, RVPAC palliation is hypothesized to offer at least comparable, if not more favorable, rehabilitation of hypoplastic right heart structures (4).

Durability of RVPAC varies significantly depending on conduit materials. Pulmonary homograft, valved expanded polytetrafluoroethylene conduit, Hancock conduit, and non-valved expanded polytetrafluoroethylene tube demonstrate a five-year freedom from conduit reoperation of 76.8%, 92.1%, 81.9%, and 80.6%, respectively (5). However, a concern of prosthetic conduits is its limited ability to accommodate patient growth. An option for prolongation of synthetic conduit palliation is partial clipping of the shunt with serial balloon dilation (2).

References

1. Ross ET, Costello JM, Backer CL, Brown LM, Robinson JD. Right ventricular outflow tract growth in infants with palliated tetralogy of fallot. Ann Thorac Surg. 2015;99(4):1367-1372.
2. Bradley SM, Erdem CC, Hsia T-YY, Atz AM, Bandisode V, Ringewald JM. Right ventricle-to-pulmonary artery shunt: alternative palliation in infants with inadequate pulmonary blood flow prior to two-ventricle repair. Ann Thorac Surg. 2008;86(1):183-188.
3. Zheng S, Yang K, Li K, Li S. Establishment of right ventricle-pulmonary artery continuity as the first-stage palliation in older infants with pulmonary atresia with ventricular septal defect may be preferable to use of an arterial shunt. Interact Cardiovasc Thorac Surg. 2014;19(1):88-94.
4. Gerelli S, Van Steenberghe M, Murtuza B, Bojan M, Harding ED, Bonnet D, et al. Neonatal right ventricle to pulmonary connection as a palliative procedure for pulmonary atresia with ventricular septal defect or severe tetralogy of Fallot. Eur J Cardiothorac Surg. 2014 Feb;45(2):278-88; discussion 288.Published online 2013.
5. Shinkawa T, Chipman C, Bozzay T, Tang X, Gossett JM, Imamura M. Outcome of right ventricle to pulmonary artery conduit for biventricular repair. Ann Thorac Surg. 2015;99(4):1357-1366.

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