Pediatric “5 Ts” of Cyanotic CHD #3: Tricuspid Disease—Tricuspid Atresia and Ebstein Anomaly

1. Overview

Within the pediatric “5 Ts” framework for cyanotic congenital heart disease, the third “T”—tricuspid disease—can be represented by two anatomically distinct lesions: tricuspid atresia (TA) and Ebstein anomaly. Both disrupt effective right-sided inflow and pulmonary blood flow, but they do so through fundamentally different mechanisms.

In tricuspid atresia, there is no effective right atrioventricular connection, and the right ventricle is hypoplastic. Systemic venous return must cross an atrial communication, while pulmonary and systemic flow depend on the ventricular communication, pulmonary outflow anatomy, ductus arteriosus, and relationship of the great arteries. Definitive management therefore follows a staged single-ventricle pathway culminating in Fontan circulation [1].

In Ebstein anomaly, the tricuspid valve is present but malformed, with apical displacement of leaflet attachment, atrialization of a portion of the right ventricle, variable right-ventricular myopathy, and often severe tricuspid regurgitation (TR). The resulting physiology ranges from nearly normal biventricular circulation to profound neonatal cyanosis and heart failure requiring urgent intervention [2].

The central principle is:

Tricuspid anatomy + right-ventricular adequacy + pulmonary blood flow determine whether the circulation can support biventricular, one-and-a-half-ventricle, or single-ventricle physiology.

2. Shared Physiologic Concept: Failure of Effective Right-Sided Flow

Normal systemic venous return follows:

RA → tricuspid valve → RV → pulmonary artery → lungs.

Both Ebstein anomaly and tricuspid atresia interfere with this pathway.

In severe Ebstein anomaly, blood can enter the RV, but severe TR and a small or dysfunctional functional RV markedly reduce effective forward pulmonary output. Elevated right atrial pressure promotes right-to-left flow across an ASD or patent foramen ovale, producing systemic desaturation.

In tricuspid atresia, the RA→RV pathway is absent altogether. Systemic venous blood must cross the atrial septum into the left atrium. Thus, an adequate atrial communication is obligatory for survival [1].

The amount of pulmonary blood flow is subsequently determined by the complete anatomy rather than by the tricuspid lesion alone. Pulmonary stenosis or atresia, VSD size, ductal patency, pulmonary vascular resistance (PVR), and great-artery relationships determine whether the patient presents predominantly with cyanosis from inadequate pulmonary blood flow or heart failure from excessive pulmonary blood flow.

Part I: Ebstein Anomaly

3. Anatomic Basis of Ebstein Anomaly

Ebstein anomaly is a congenital malformation involving both the tricuspid valve and right ventricular myocardium. The septal and inferior components of the valve are displaced apically to varying degrees, while incomplete leaflet delamination, abnormal leaflet attachment, and distortion of the functional annulus contribute to TR [2,3].

The morphologic RV can therefore be divided into:

• An atrialized RV between the true tricuspid annulus and displaced functional valve.
• A smaller functional RV distal to the displaced valve.
• A variable RV outflow component responsible for antegrade pulmonary flow.

The anterior leaflet is often large and mobile but may have abnormal attachments that limit effective coaptation. The resulting hemodynamic severity cannot be predicted from leaflet displacement alone. Functional RV size, RV myocardial performance, severity of TR, pulmonary outflow, and associated lesions must all be considered.

This explains the broad clinical spectrum of Ebstein anomaly. Some patients have relatively preserved forward flow and remain stable for years, whereas others have a markedly enlarged right atrium, severe TR, severe RV dysfunction, and profound neonatal circulatory compromise [2].

4. Why Ebstein Anomaly Causes Cyanosis

Cyanosis in Ebstein anomaly results primarily from the interaction between ineffective RV output and right-to-left atrial shunting.

With severe TR, a substantial component of RV stroke volume is ejected backward into the right atrium rather than forward into the pulmonary artery. Right atrial pressure rises, promoting right-to-left shunting through an ASD or PFO:

Severe TR → elevated RA pressure → right-to-left atrial shunt → systemic desaturation.

The functional RV may also be too small or dysfunctional to generate adequate antegrade pulmonary flow. This is particularly important during the neonatal period, when PVR remains physiologically elevated.

A severely affected newborn may therefore demonstrate little or no effective antegrade pulmonary blood flow despite an anatomically patent pulmonary outflow tract. In a contemporary neonatal surgical series, only 2 of 8 operated patients had antegrade pulmonary blood flow, emphasizing the importance of functional rather than purely anatomic assessment [4].

The neonatal circulation may improve as PVR falls after birth. Consequently, aggressive initial medical stabilization can allow selected infants to transition toward more favorable biventricular physiology rather than proceeding immediately to surgery [3,7].

5. Clinical Assessment and Determination of RV Adequacy

The crucial question in Ebstein anomaly is not simply whether the tricuspid valve is abnormal, but whether the functional RV and reconstructed tricuspid valve can support an effective pulmonary circulation.

Assessment should integrate:

• Severity and mechanism of TR
• Functional RV size and systolic performance
• Degree of atrialization
• Presence of antegrade pulmonary blood flow
• Pulmonary valve and RV outflow anatomy
• PVR
• LV function
• Degree of cyanosis
• Heart failure and end-organ dysfunction
• Associated arrhythmias

Echocardiography remains central to evaluating valve morphology, TR, chamber dimensions, RV function, and pulmonary flow. Cardiac magnetic resonance imaging can provide additional assessment of RV volumes and ventricular function in older patients [2].

The anatomy therefore exists on a continuum. At one end, the RV is capable of supporting the complete pulmonary circulation after tricuspid repair. At the other, the RV is too small or dysfunctional to contribute meaningfully, making single-ventricle palliation more appropriate. Between these extremes lies the potential role of one-and-a-half-ventricle repair.

6. Neonatal Management of Severe Ebstein Anomaly

Severely affected neonates may present with cyanosis, heart failure, acidosis, cardiomegaly, inadequate pulmonary blood flow, and end-organ dysfunction. Management should initially focus on systemic oxygen delivery and stabilization while determining whether the circulation can improve as PVR decreases.

Medical management may include optimization of ventilation, correction of acidosis, appropriate inotropic support, and management of pulmonary and systemic vascular resistance. Ductal management should be individualized according to pulmonary blood flow and overall circulatory physiology.

When medical therapy succeeds, delaying intervention may permit improved antegrade pulmonary flow as neonatal PVR declines. This observation supports an anatomy- and physiology-based rather than diagnosis-based approach to intervention [7].

Persistent cyanosis, heart failure, maldistribution of cardiac output, or end-organ dysfunction despite stabilization indicates the need for surgical treatment. In one contemporary cohort of 18 symptomatic neonates, 8 required operation; indications among the operated patients commonly included cyanosis and heart failure, end-organ dysfunction, and abnormal distribution of cardiac output [4].

7. Biventricular Repair

When the functional RV is adequate, preservation of a biventricular circulation is preferred.

Modern repair aims to restore tricuspid competence while preserving useful RV myocardium. The cone reconstruction has become an important contemporary technique. Available leaflet tissue is mobilized and reconstructed into a circumferential cone that coapts at or near the true tricuspid annulus. Contemporary reviews consider modified cone reconstruction the preferred repair for many suitable patients [2,3].

Repair may be accompanied by:

• Right atrial reduction
• Plication or remodeling of the atrialized RV
• ASD closure or controlled fenestration
• Treatment of accessory pathways or other arrhythmia substrates

The objective is not simply reduction of TR. Successful repair must produce a circulation in which the functional RV can accept systemic venous return and generate sufficient pulmonary blood flow without excessive filling pressure.

8. One-and-a-Half-Ventricle Repair

A marginal RV may be capable of contributing meaningful antegrade pulmonary flow but unable to accept the entire systemic venous return. In this setting, a bidirectional Glenn connection can divert superior vena caval blood directly to the pulmonary arteries and unload the RV.

This creates a one-and-a-half-ventricle circulation:

SVC → pulmonary arteries directly

while

IVC → RA → repaired tricuspid valve → RV → pulmonary artery.

This strategy preserves RV contribution to pulmonary blood flow while reducing RV preload and may expand the feasibility of valve repair in selected borderline patients [3].

In a 47-patient surgical series using a bicuspidization repair strategy, 29% underwent an associated Glenn procedure. Initial tricuspid repair was successful in 91%, although 17% subsequently required reoperation and 4% underwent valve replacement [6]. These results support the concept that partial cavopulmonary unloading can be useful when the RV is marginal rather than completely inadequate.

9. Single-Ventricle Palliation and the Starnes Strategy

When the RV and tricuspid valve cannot support effective biventricular circulation, single-ventricle palliation may provide the safer pathway.

For critically ill neonates, the Starnes strategy functionally excludes the RV using closure of the tricuspid orifice, usually with a fenestrated patch, combined with decompression/remodeling of the right-sided chambers and provision of pulmonary blood flow when required.

Early experience illustrates both the severity of the underlying disease and the importance of surgical technique. In a 16-neonate series, hospital mortality was 31%. Survival was 80% among patients receiving a fenestrated tricuspid patch compared with 33% with a nonfenestrated patch. Survivors subsequently underwent bidirectional Glenn palliation, although only a subset had reached Fontan completion at the time of follow-up [5].

More recent experience suggests that outcomes can improve when intervention is specifically matched to anatomy and physiology. In the contemporary neonatal series noted above, there was one operative death among eight operated patients and no late deaths during extended follow-up [4]. These data are encouraging but remain based on small retrospective cohorts.

Part II: Tricuspid Atresia

10. Fundamental Anatomy and Obligatory Atrial Shunting

Tricuspid atresia is defined by absence of the normal right atrioventricular connection with associated RV hypoplasia [1].

Systemic venous blood entering the right atrium cannot reach the RV directly:

Systemic veins → RA → ASD/PFO → LA → LV.

An adequate atrial communication is therefore obligatory. Unlike Ebstein anomaly, where right-to-left atrial shunting varies with right-sided pressure and RV performance, atrial-level shunting in tricuspid atresia is an essential component of the circulation.

The LV becomes the dominant ventricle. A hypoplastic RV outlet chamber is generally connected to the dominant ventricle through a VSD or bulboventricular foramen. The functional importance of this communication depends critically on the great-artery relationship.

11. Great-Artery Relationship and Outflow Physiology

With normally related great arteries, the aorta arises from the dominant LV, whereas pulmonary blood flow reaches the pulmonary artery through the VSD and hypoplastic RV outlet chamber. The amount of pulmonary blood flow therefore depends on VSD size and the severity of pulmonary stenosis or pulmonary atresia.

A restrictive pulmonary pathway produces severe cyanosis and may create ductal-dependent pulmonary blood flow.

In contrast, with transposed great arteries, the pulmonary artery arises from the dominant LV and the aorta arises from the hypoplastic outlet chamber. Systemic output must therefore pass through the VSD or bulboventricular foramen before reaching the aorta.

In this configuration:

The ventricular communication becomes part of the systemic outflow tract.

Progressive restriction can consequently produce systemic ventricular outflow obstruction. Associated arch obstruction further increases the importance of recognizing the entire systemic outflow pathway when planning palliation.

12. Balancing Pulmonary Blood Flow

The neonatal presentation of tricuspid atresia is determined largely by pulmonary blood flow.

When pulmonary flow is inadequate because of severe pulmonary stenosis, pulmonary atresia, or restrictive ventricular communication, the infant develops marked cyanosis. Ductal patency or another reliable source of pulmonary blood flow may be required.

Conversely, when pulmonary outflow is relatively unrestricted, pulmonary blood flow may become excessive as PVR falls. The infant may then develop tachypnea, feeding difficulty, ventricular volume overload, and congestive heart failure.

Thus, the therapeutic objective is not maximal pulmonary blood flow but balanced pulmonary and systemic circulation that preserves systemic oxygen delivery without excessive volume loading of the single ventricle.

13. Staged Single-Ventricle Palliation

Because the RV is intrinsically inadequate for conventional biventricular repair, tricuspid atresia generally follows staged single-ventricle palliation [1].

Initial management is anatomy dependent. Patients with satisfactory pulmonary blood flow and unobstructed systemic output may not require neonatal surgery. Inadequate pulmonary blood flow requires establishment of a stable pulmonary source, whereas excessive pulmonary blood flow may require pulmonary artery restriction. Systemic outflow obstruction requires separate reconstruction and may necessitate a Damus–Kaye–Stansel or more comprehensive neonatal outflow strategy depending on the anatomy.

The second stage is the bidirectional Glenn, which directs superior vena caval blood directly to the pulmonary arteries and reduces ventricular volume load.

Fontan completion subsequently directs the remaining systemic venous return to the pulmonary arteries, leaving the single dominant ventricle responsible primarily for systemic output.

14. Fontan Physiology and Long-Term Implications

Fontan circulation eliminates a subpulmonary ventricle. Pulmonary blood flow therefore depends on the pressure gradient between the systemic veins and pulmonary venous atrium rather than on ventricular propulsion.

The circulation is consequently preload dependent and highly sensitive to elevated PVR. Chronic systemic venous hypertension is necessary to drive pulmonary blood flow, while reduced ventricular preload limits cardiac output [1].

These characteristics explain many long-term Fontan complications, including:

• Arrhythmias
• Systemic venous hypertension
• Lymphatic dysfunction
• Hepatic congestion and Fontan-associated liver disease
• Thrombotic complications
• Progressive limitation of cardiac output
• Fontan circulatory failure

Perioperative management must therefore preserve venous return, maintain low PVR, avoid excessive positive-pressure ventilation when possible, and support ventricular function and sinus rhythm [1].

15. Surgical Decision Framework

The most useful conceptual distinction between the two diseases is the potential adequacy of the RV.

In tricuspid atresia, the absent right atrioventricular connection and hypoplastic RV make a conventional biventricular circulation unattainable; treatment is directed toward staged single-ventricle palliation.

In Ebstein anomaly, RV capability exists on a continuum. A sufficiently sized and functional RV favors biventricular tricuspid repair. A marginal RV may benefit from Glenn unloading and one-and-a-half-ventricle repair. An inadequate RV with severe neonatal circulatory failure may require single-ventricle palliation.

Current evidence supports this individualized anatomy- and physiology-based strategy, but comparative data remain limited. Most surgical evidence consists of retrospective institutional series with relatively small patient numbers, particularly for critically ill neonates [4-6]. Accordingly, anatomy, ventricular function, pulmonary blood flow, and the balance between cyanosis and heart failure remain more useful for decision-making than a rigid diagnosis-based algorithm.

16. Key Concept

The “Tri-cuspid” component of the pediatric 5 Ts encompasses two different routes to cyanosis.

In Ebstein anomaly, severe TR, atrialization of the RV, RV myopathy, and inadequate functional RV output can elevate RA pressure and drive systemic venous blood across an atrial communication. Surgical management ranges from biventricular valve repair to Glenn-assisted one-and-a-half-ventricle repair or single-ventricle palliation.

In tricuspid atresia, there is no RA→RV connection. Atrial-level shunting is obligatory, and pulmonary versus systemic blood flow is determined by VSD anatomy, pulmonary outflow, ductal patency, and great-artery relationships. The circulation therefore progresses toward staged cavopulmonary palliation and Fontan physiology.

For both lesions, the operative strategy follows the same fundamental question:

Where can the systemic venous blood go, how much effective pulmonary blood flow can be generated, and is the right ventricle capable of supporting it?

References

[1] Garrity M, Poppers J, Richman D, Bacon J. Tricuspid Atresia and Fontan Circulation: Anatomy, Physiology, and Perioperative Considerations. Hearts. 2025. doi:10.3390/hearts6040030.

[2] Neumann S, Rüffer A, Sachweh J, Biermann D, Herrmann J, Jerosch-Herold M, et al. Narrative review of Ebstein's anomaly beyond childhood: imaging, surgery, and future perspectives. Cardiovasc Diagn Ther. 2021. doi:10.21037/CDT-20-771.

[3] Sainathan S, da Fonseca da Silva L, da Silva JP. Ebstein’s anomaly: contemporary management strategies. J Thorac Dis. 2020. doi:10.21037/jtd.2020.01.18.

[4] Pizarro C, Bhat M, Davis DA, Duncan DR, Pelletier G, Baffa G. Tailored strategy to match anatomy and physiology with intervention can improve outcomes of symptomatic neonates with Ebstein anomaly. JTCVS Open. 2022. doi:10.1016/j.xjon.2022.09.007.

[5] Reemtsen B, Fagan BT, Wells WJ, Starnes VA. Current surgical therapy for Ebstein anomaly in neonates. J Thorac Cardiovasc Surg. 2006. doi:10.1016/j.jtcvs.2006.08.044.

[6] Mainwaring RD, Rosenblatt TR, Lui G, Ma M, Hanley FL. Surgical repair of Ebstein's anomaly utilizing a bicuspidization approach. Ann Thorac Surg. 2019. doi:10.1016/j.athoracsur.2019.06.026.

[7] Vouhé P. Management of neonatal Ebstein's anomaly: towards a rational approach? Eur J Cardiothorac Surg. 2014. doi:10.1093/ejcts/ezt457.