Tricuspid Atresia #5: First Palliation — PGE1, Ductal Stent, Systemic-to-Pulmonary Shunt, and PA Banding

Introduction

The first-stage management of tricuspid atresia (TA) is driven by the balance between pulmonary blood flow (Qp) and systemic blood flow (Qs). Because there is no direct right atrium–right ventricle connection, pulmonary blood flow depends on alternative pathways, including the ventricular septal defect or bulboventricular foramen, ductus arteriosus, great artery relationship, and degree of pulmonary or systemic outflow obstruction.

The goal of initial palliation is not simply to increase or decrease pulmonary flow. The goal is to create a stable balance between pulmonary blood flow and systemic output while preserving ventricular function, pulmonary artery growth, and the pathway to superior cavopulmonary connection and Fontan completion.

Contemporary outcome data support an individualized approach. In a 105-patient infant TA cohort, Alsoufi et al. reported 84% overall 8-year survival, with survival not significantly affected by the type of initial palliation, including modified Blalock-Taussig shunt, Norwood-type palliation, or pulmonary artery banding [1]. However, procedure selection remains strongly morphology-dependent, and earlier multi-institutional data showed that matching the initial procedure to anatomy and physiology improves outcomes in neonates with TA [2].

1. Core Physiologic Objective: Balance Qp and Qs

Initial palliation should achieve the following:

• Maintain adequate systemic oxygen delivery
• Avoid severe cyanosis from inadequate pulmonary blood flow
• Avoid pulmonary overcirculation and systemic hypoperfusion
• Prevent excessive ventricular volume loading
• Protect the pulmonary vascular bed
• Preserve branch pulmonary artery anatomy
• Maintain a favorable pathway toward Glenn and Fontan circulation

The practical question is therefore:

Is the patient’s dominant problem too little pulmonary blood flow, too much pulmonary blood flow, or systemic outflow obstruction?

2. Patients With Decreased Pulmonary Blood Flow

Typical Anatomy

Low pulmonary blood flow occurs when pulmonary outflow is severely restricted or absent.

Typical examples include:

• Type Ia: pulmonary atresia with normally related great arteries
• Type IIa: pulmonary atresia with transposed great arteries
• Severe pulmonary stenosis or restrictive pulmonary outflow physiology

In these patients, systemic output is relatively preserved, but pulmonary blood flow is inadequate. Oxygen saturation is usually ductal-dependent in the neonatal period.

3. PGE1: Initial Stabilization for Ductal-Dependent Pulmonary Blood Flow

Prostaglandin E1 (PGE1) is the initial medical therapy when pulmonary blood flow is ductal-dependent.

The purpose of PGE1 is to:

• Maintain ductal patency
• Improve pulmonary blood flow
• Stabilize systemic oxygen saturation
• Provide time for anatomic assessment
• Bridge the patient to catheter-based or surgical palliation

PGE1 is a stabilizing therapy, not definitive palliation. Once the patient is stabilized, the team must decide whether durable pulmonary blood flow is best provided by ductal stenting or a systemic-to-pulmonary artery shunt.

4. Ductal Stenting

Concept

Ductal stenting maintains pulmonary blood flow by keeping the ductus arteriosus open with a transcatheter stent.

Potential advantages include:

• Avoidance of neonatal thoracotomy or sternotomy
• Avoidance of cardiopulmonary bypass in selected patients
• Shorter early recovery in appropriate anatomy
• Potentially favorable early ICU course
• Preservation of surgical options for later stages

In a contemporary univentricular heart cohort comparing ductus stenting with surgical systemic-to-pulmonary shunt, hospital mortality was comparable between ductal stenting and shunt palliation, while ductal stenting was associated with shorter ICU and hospital stays. This benefit was offset by a higher incidence of acute stent-related complications and need for careful reintervention planning [3].

Important Anatomic Considerations

Ductal stenting is most favorable when:

• The ductal anatomy is technically suitable
• Branch pulmonary arteries can be supplied without distortion
• The ductus does not insert in a way that creates unilateral pulmonary artery stenosis
• The patient can tolerate catheter-based palliation
• The interstage monitoring system is robust

Ductal stenting is less attractive when the ductus is highly tortuous, inserts unfavorably into a branch pulmonary artery, or when pulmonary artery anatomy would be compromised by the stent.

5. Systemic-to-Pulmonary Artery Shunt

Concept

A systemic-to-pulmonary artery shunt, typically a modified Blalock-Taussig-Thomas shunt, provides a durable source of pulmonary blood flow by connecting the systemic arterial circulation to a pulmonary artery.

The shunt:

• Increases pulmonary blood flow
• Improves systemic oxygen saturation
• Provides reliable palliation until Glenn
• Allows growth before the next stage

Limitations and Risks

Important risks include:

• Shunt thrombosis
• Excessive pulmonary blood flow
• Diastolic runoff and systemic hypoperfusion
• Pulmonary artery distortion
• Interstage mortality
• Need for precise shunt size selection

In the Congenital Heart Surgeons’ Society study of 303 infants with Type I TA, systemic-to-pulmonary shunt patients represented a higher-risk subgroup. Risk-adjusted 6-year survival was lower after systemic-to-pulmonary shunt than after pulmonary artery banding or superior cavopulmonary connection. Outcomes were worse when competitive pulmonary blood flow was poorly controlled, particularly with an open ductus arteriosus after shunt placement [4].

Surgical Principle

When a systemic-to-pulmonary shunt is selected, the surgeon must avoid both extremes:

• Too small: persistent cyanosis and shunt thrombosis risk
• Too large: pulmonary overcirculation, ventricular volume load, low diastolic pressure, and systemic hypoperfusion

The shunt must be sized to provide adequate oxygenation without compromising systemic output.

6. Patients With Excessive Pulmonary Blood Flow

Typical Anatomy

Excessive pulmonary blood flow occurs when there is little or no pulmonary stenosis and pulmonary flow is unrestricted.

Typical examples include:

• Type Ic: normally related great arteries, no pulmonary stenosis, large VSD
• Type IIc: transposed great arteries, no pulmonary stenosis, with a large pulmonary outflow pathway

These patients may initially appear less cyanotic but can develop:

• Tachypnea
• Poor feeding
• Failure to thrive
• Pulmonary edema
• Ventricular volume overload
• Reduced systemic output
• Elevated pulmonary artery pressure

The physiologic problem is not cyanosis alone. The dominant problem is pulmonary overcirculation with systemic steal.

7. Pulmonary Artery Banding

Concept

Pulmonary artery banding (PAB) increases resistance to pulmonary blood flow by narrowing the main pulmonary artery.

The intended effects are:

• Reduce excessive pulmonary blood flow
• Improve effective systemic output
• Reduce ventricular volume overload
• Lower pulmonary artery pressure
• Protect the pulmonary vascular bed
• Stabilize the patient until Glenn

PAB is most appropriate when the patient has excessive pulmonary blood flow and no significant systemic outflow obstruction.

Technical Objective

The band should be tight enough to reduce pulmonary overcirculation but not so tight that it causes severe cyanosis, ventricular dysfunction, or distortion of the branch pulmonary arteries.

The target is physiologic balance, not a fixed anatomic diameter.

8. Special Concern in Type II Tricuspid Atresia

Type II TA requires particular caution because of the relationship between the great arteries and systemic outflow.

In Type II TA:

• The great arteries are transposed.
• The pulmonary artery usually arises from the dominant left ventricle.
• The aorta arises from the hypoplastic right ventricle.
• Systemic output may depend on flow across the VSD or bulboventricular foramen into the right ventricle and aorta.

Therefore, the VSD or bulboventricular foramen is not merely a pulmonary flow pathway. It may be the systemic outflow pathway.

This creates a critical surgical issue:

Pulmonary artery banding can reduce pulmonary overcirculation, but it may also increase ventricular pressure and unmask or worsen subaortic obstruction if the bulboventricular foramen is restrictive.

In this setting, isolated PA banding may be insufficient or harmful. The surgeon must evaluate:

• BVF/VSD size
• Doppler gradient across the systemic outflow pathway
• Aortic valve and ascending aortic size
• Arch anatomy
• Ventricular pressure loading
• Presence or risk of progressive subaortic obstruction
• Need for systemic outflow reconstruction

Although systemic outflow anatomy is central to operative decision-making, available first-palliation comparative studies do not provide a consistent BVF size threshold that can be applied universally. Therefore, BVF assessment should be integrated with the entire physiologic and anatomic picture rather than used as an isolated metric.

9. How to Choose the First Palliation

10. Evidence-Based Interpretation

Current evidence suggests that survival after first-stage palliation in TA is influenced not only by the selected procedure but also by the underlying morphology and physiologic substrate.

Alsoufi et al. reported that overall survival in infants with TA was acceptable in the contemporary era and that survival was not statistically different by initial palliation type, including modified Blalock-Taussig shunt, Norwood-type palliation, and pulmonary artery banding [1]. This supports the concept that different strategies can be appropriate when selected for the correct anatomy.

Karamlou et al. emphasized that outcomes improve when the procedure is matched to morphology, including careful attention to shunt size and the transition to cavopulmonary connection [2]. This is particularly relevant because TA is not a single physiologic entity; Type I and Type II anatomy present different risks.

Wilder et al. showed that in Type I TA, systemic-to-pulmonary shunt patients had lower risk-adjusted survival compared with pulmonary artery banding or superior cavopulmonary connection, especially when competitive pulmonary blood flow through the ductus or main pulmonary artery was not controlled [4]. This finding reinforces the importance of managing all pulmonary blood flow sources, not simply placing a shunt.

Grozdanov et al. showed that ductal stenting and surgical shunt palliation can have comparable early survival in ductal-dependent univentricular physiology, with ductal stenting offering shorter ICU and hospital stays but more acute stent-related complications [3]. Thus, ductal stenting is best viewed as an anatomy-dependent alternative rather than a universal replacement for surgical shunting.

11. Surgical Pearls

• The first palliation in tricuspid atresia is a physiology-balancing operation.
• Low pulmonary blood flow requires ductal support with PGE1, followed by ductal stenting or systemic-to-pulmonary shunt.
• Excessive pulmonary blood flow may require pulmonary artery banding to protect the pulmonary vascular bed and improve systemic output.
• In Type I TA, systemic-to-pulmonary shunting must avoid uncontrolled competitive pulmonary blood flow through the PDA or main pulmonary artery.
• In Type II TA, the VSD or bulboventricular foramen may be the systemic outflow pathway; PA banding can unmask or worsen subaortic obstruction.
• The best initial palliation is the one that matches the patient’s anatomy, pulmonary blood flow, systemic output, and pathway to Glenn and Fontan.

References

[1] Alsoufi B, Schlosser B, Mori M, McCracken C, Slesnick T, Kogon B, Petit CJ, Sachdeva R, Kanter K. Influence of morphology and initial surgical strategy on survival of infants with tricuspid atresia. Ann Thorac Surg. 2015;100(4):1403-1409; discussion 1409-1410.

[2] Karamlou T, Ashburn DA, Caldarone CA, Blackstone EH, Jonas RA, Jacobs ML, Williams WG, Ungerleider RM, McCrindle BW. Matching procedure to morphology improves outcomes in neonates with tricuspid atresia. J Thorac Cardiovasc Surg. 2005;130(6):1503-1510.

[3] Grozdanov D, Osawa T, Borgmann K, Schaeffer T, Staehler H, Di Padua C, Heinisch P, Piber N, Georgiev S, Hager A, Ewert P, Hörer J, Ono M. Comparison of ductus stent versus surgical systemic-to-pulmonary shunt as initial palliation in patients with univentricular heart. Eur J Cardiothorac Surg. 2024;65(3):ezae011.

[4] Wilder TJ, Ziemer G, Hickey EJ, Gruber PJ, Karamlou T, Kirshbom PM, Blackstone EH, DeCampli WM, Williams WG, McCrindle BW. Surgical management of competing pulmonary blood flow affects survival before Fontan/Kreutzer completion in patients with tricuspid atresia type I. J Thorac Cardiovasc Surg. 2015;150(5):1222-1230.e7.