When the Tricuspid Valve Develops Too Low in the Right Ventricle
Introduction
Congenital cardiac defects can often be understood by asking:
Where is the valve?
Can the right ventricle generate effective forward flow?
And is deoxygenated blood being forced across the atrial septum into the systemic circulation?
Ebstein Anomaly is a congenital abnormality of the tricuspid valve and right ventricle.
In severe disease, the valve is displaced downwards into the right ventricle, the right atrium becomes massively enlarged, effective right ventricular function is reduced, and significant tricuspid regurgitation develops.
If forward pulmonary blood flow becomes inadequate, venous blood can cross an ASD or PFO from right to left.
The result is the blue baby.
Yet Ebstein Anomaly is extraordinarily variable. Some patients present critically ill at birth, while others remain relatively well until childhood or adulthood. (www.heart.org)
Body
What is Ebstein Anomaly?
Ebstein Anomaly is a congenital malformation of the tricuspid valve.
Normally:
Right atrium → Tricuspid valve → Right ventricle → Pulmonary artery
The tricuspid valve normally sits at the junction between the right atrium and right ventricle.
In Ebstein Anomaly, the septal and posterior tricuspid valve leaflets are displaced apically, meaning downwards towards the apex of the right ventricle.
The valve therefore functions from a position that is too low within the heart.
This has two major consequences:
- part of the anatomical right ventricle becomes incorporated functionally into the right atrium;
- and the remaining functional right ventricle may be too small or inefficient to provide normal pulmonary blood flow. (www.heart.org)
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Atrialisation of the Right Ventricle
The portion of the right ventricle lying between the normal tricuspid annulus and the displaced valve is often described as the atrialised right ventricle.
Anatomically it is ventricular tissue.
Functionally, however, it behaves as part of the right atrium.
This produces an unusually large right-sided chamber consisting of:
Right atrium + atrialised right ventricle
while the remaining functional right ventricular cavity can be relatively small.
This phenomenon is known as atrialisation of the right ventricle.
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The Tricuspid Valve
The tricuspid valve in Ebstein Anomaly is not simply positioned incorrectly.
The valve leaflets themselves may also be abnormal.
They may be:
- displaced;
- elongated;
- adherent to the ventricular wall;
- fenestrated;
- poorly mobile;
- or severely malformed.
The anterior leaflet is often large and sail-like.
The septal and posterior leaflets are more characteristically displaced.
These abnormalities mean the valve frequently fails to close effectively.
The result is tricuspid regurgitation.
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Tricuspid Regurgitation
During right ventricular contraction, blood should move forwards through the pulmonary valve.
In severe Ebstein Anomaly, a substantial proportion instead leaks backwards through the abnormal tricuspid valve.
Thus:
Right ventricle → Right atrium
rather than exclusively:
Right ventricle → Pulmonary artery
The right atrium becomes progressively enlarged.
The ventricle loses effective forward stroke volume.
The more severe the regurgitation, the less effective the right heart becomes at supplying the pulmonary circulation. (www.heart.org)
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Why is the Baby Blue?
Many patients with Ebstein Anomaly have an Atrial Septal Defect or Patent Foramen Ovale.
As right atrial pressure rises, venous blood can cross this opening from right to left.
Thus:
Right atrium → ASD/PFO → Left atrium → Left ventricle → Aorta
Deoxygenated systemic venous blood therefore bypasses the lungs and enters the systemic arterial circulation.
The infant becomes cyanosed.
The degree of cyanosis depends upon:
- severity of tricuspid regurgitation;
- effective right ventricular output;
- pulmonary vascular resistance;
- pulmonary valve function;
- atrial communication;
- and ductal physiology.
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A Spectrum Rather Than One Lesion
Ebstein Anomaly is one of the best examples of congenital cardiac disease existing on a wide spectrum.
At the mild end:
- tricuspid displacement may be modest;
- regurgitation may be mild;
- right ventricular function may be preserved;
- and the patient may be asymptomatic for years.
At the severe neonatal end:
- the tricuspid valve may be profoundly displaced;
- the right ventricle may generate little effective forward flow;
- the right atrium may be enormous;
- cyanosis may be severe;
- pulmonary blood flow may be critically reduced;
- and the circulation can become life-threatening immediately after birth. (PubMed Central (PMC))
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Functional Pulmonary Atresia
In severe neonatal Ebstein Anomaly, the pulmonary valve itself may be anatomically open.
Yet no effective forward blood flow passes through it.
This is known as functional pulmonary atresia.
Why?
The right ventricle may be unable to generate sufficient pressure to overcome the high pulmonary vascular resistance present immediately after birth.
Severe tricuspid regurgitation further reduces effective forward output.
Blood therefore fails to travel:
Right ventricle → Pulmonary artery
despite the absence of a physically atretic pulmonary valve.
This distinguishes functional pulmonary atresia from true anatomical pulmonary atresia.
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The Importance of Pulmonary Vascular Resistance
Pulmonary vascular resistance is naturally high in the newborn immediately after birth.
Normally it falls as the lungs expand and oxygenation improves.
For a severely compromised right ventricle, this fall can be enormously important.
As PVR decreases, forward pulmonary flow may improve.
Some critically cyanosed neonates can therefore improve substantially during the first days of life if the circulation can be supported safely while PVR falls. (PubMed Central (PMC))
This is one reason not every neonate with severe-looking Ebstein anatomy immediately undergoes surgery.
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The Ductus Arteriosus
The ductus arteriosus may initially provide an additional route for pulmonary blood flow:
Aorta → PDA → Pulmonary arteries
In a neonate with poor antegrade pulmonary flow, maintaining ductal patency may therefore sometimes be helpful.
However, Ebstein physiology contains an important complication:
the ductus can also become part of a harmful circular shunt.
Current neonatal management therefore depends on the precise haemodynamics rather than simply maintaining the PDA in every case. (PubMed)
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Circular Shunt
One of the most important severe forms of neonatal Ebstein physiology is the circular shunt.
This can occur when severe tricuspid regurgitation is combined with significant pulmonary regurgitation and a patent ductus arteriosus.
Blood can circulate around an ineffective loop:
Aorta → PDA → Pulmonary artery → Pulmonary valve backwards → Right ventricle → Tricuspid valve backwards → Right atrium → ASD → Left heart → Aorta
A large amount of cardiac output can therefore circulate around the heart without effectively perfusing either the body or lungs.
This is profoundly inefficient and can cause severe haemodynamic instability.
Current expert guidance considers an unstable neonate with a circular shunt to require urgent interruption of that circulation. (PubMed)
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The Enlarged Right Atrium
Severe tricuspid regurgitation produces a very large right atrium.
In extreme neonatal cases the heart can become massively enlarged.
This is not simply an imaging curiosity.
An enormous heart occupies thoracic space.
It can physically compress the lungs and interfere with normal pulmonary development and ventilation.
Severe cardiomegaly is consequently an important adverse feature in neonatal Ebstein Anomaly. (PubMed Central (PMC))
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ASD and PFO
An atrial communication is extremely common in Ebstein Anomaly.
In severe neonatal disease, it may be essential for survival because it provides an escape route for systemic venous blood when right ventricular forward flow is inadequate.
However, it also permits right-to-left shunting and cyanosis.
In less severe disease, shunting may be intermittent and become more prominent during exercise or when right-sided pressures rise.
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Arrhythmias
Ebstein Anomaly has a particularly important association with cardiac arrhythmias.
Abnormal conduction pathways are more common than in the general population.
A particularly recognised association is Wolff–Parkinson–White syndrome — WPW.
Accessory conduction pathways can permit episodes of supraventricular tachycardia — SVT. (www.heart.org)
Patients may therefore present with:
- palpitations;
- rapid heart rate;
- dizziness;
- syncope;
- or haemodynamic instability.
Arrhythmia management forms an important part of both childhood and adult follow-up.
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Wolff–Parkinson–White Syndrome
Normally electrical impulses travel from the atria to the ventricles through the AV node.
In WPW, an additional electrical connection bypasses part of the normal conduction system.
This accessory pathway can form part of a re-entry circuit and produce rapid tachyarrhythmias.
The abnormal tricuspid valve region in Ebstein Anomaly is particularly associated with accessory pathways.
Catheter ablation may be used to eliminate clinically significant pathways. (www.heart.org)
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Presentation in the Neonate
Severe neonatal Ebstein Anomaly may present with:
- cyanosis;
- tachypnoea;
- respiratory distress;
- marked cardiomegaly;
- low cardiac output;
- poor pulmonary blood flow;
- severe tricuspid regurgitation;
- right heart failure;
- and cardiogenic shock.
The severity is determined not merely by the appearance of the valve but by whether the right ventricle can provide effective pulmonary circulation. (PubMed)
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Presentation Later in Life
Milder forms may present in childhood or adulthood.
Symptoms can include:
- reduced exercise tolerance;
- exertional breathlessness;
- cyanosis;
- palpitations;
- SVT;
- fatigue;
- right-sided heart failure;
- or incidental murmur.
Some patients remain minimally symptomatic for many years.
This variability explains why Ebstein Anomaly can appear in both neonatal congenital surgery and adult congenital cardiology.
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Diagnosis
Echocardiography
Echocardiography is central to diagnosis.
It assesses:
- displacement of the tricuspid valve;
- leaflet anatomy;
- severity of tricuspid regurgitation;
- size of the functional right ventricle;
- atrialised right ventricular volume;
- right atrial enlargement;
- atrial communications;
- pulmonary valve function;
- and ventricular function.
Doppler imaging can assess the severity and direction of abnormal blood flow.
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ECG
An ECG may demonstrate:
- right atrial enlargement;
- conduction abnormalities;
- bundle branch block patterns;
- pre-excitation;
- or arrhythmias associated with accessory pathways.
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Cardiac MRI
Cardiac MRI can provide detailed information about:
- right ventricular size;
- right ventricular function;
- atrialised ventricular volume;
- tricuspid regurgitation;
- and overall cardiac anatomy.
It becomes particularly useful in older children and adults being considered for intervention.
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Initial Neonatal Management
Not every critically appearing neonatal Ebstein patient requires immediate surgery.
Initial management may aim to support the child while pulmonary vascular resistance falls.
This may involve:
- ventilation;
- oxygenation;
- correction of acidosis;
- careful inotropic support;
- optimisation of systemic perfusion;
- management of pulmonary blood flow;
- and close assessment of ductal physiology.
In selected infants with inadequate pulmonary blood flow, prostaglandin may initially be used.
However, if ductal flow contributes to pulmonary regurgitation and a circular shunt, ductal closure rather than continued patency may become desirable. (PubMed Central (PMC))
Again:
treatment follows physiology.
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When is Surgery Required?
Surgery is considered when symptoms or haemodynamics cannot be adequately managed medically.
Indications can include:
- severe tricuspid regurgitation;
- progressive right ventricular dysfunction;
- significant cyanosis;
- worsening exercise capacity;
- cardiomegaly;
- recurrent arrhythmia;
- or critical neonatal haemodynamic instability.
The operation chosen depends heavily upon age, valve anatomy and whether the right ventricle is capable of supporting a two-ventricle circulation.
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The Cone Repair
For many children and adults requiring surgery, the modern preferred tricuspid valve reconstruction is the cone repair, developed by Brazilian surgeon José Pedro da Silva.
Rather than simply reducing the size of the valve opening, the surgeon mobilises the available tricuspid leaflet tissue.
The leaflet tissue is rotated and reconstructed into a cone-shaped valve around the true tricuspid annulus.
The objective is to create a more anatomically normal valve with effective leaflet-to-leaflet closure.
The cone repair has become an important contemporary surgical strategy for Ebstein Anomaly. (PubMed Central (PMC))
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Reduction of the Atrialised Right Ventricle
During surgical reconstruction, the massively enlarged atrialised portion of the right ventricle may also be reduced.
This can improve ventricular geometry.
A very large right atrium may similarly be reduced by reduction atrioplasty.
The aim is not simply cosmetic.
Reducing excessive chamber size can improve cardiac mechanics and provide more space within the thorax for the lungs.
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ASD Closure
The atrial communication may be closed during definitive repair.
However, in patients with borderline right ventricular function, complete closure may not always be desirable.
A small residual or deliberately created communication can act as a pressure-relief pathway.
The exact strategy depends upon the patient’s haemodynamics.
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One-and-a-Half Ventricle Repair
Some patients have a right ventricle capable of providing useful output but not enough to handle the entire systemic venous return.
In this situation, a Bidirectional Glenn may be added to tricuspid valve repair.
The SVC is connected directly to the pulmonary arteries.
This removes a substantial portion of venous return from the right ventricle.
The right ventricle continues to provide some pulmonary flow, while the Glenn provides the remainder.
This is known as a one-and-a-half ventricle repair.
It lies physiologically between a full two-ventricle repair and a Fontan circulation.
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The Critically Ill Neonate
The sickest neonates present a very different surgical problem from the older child undergoing elective cone repair.
The right ventricle may be profoundly inadequate.
There may be:
- severe tricuspid regurgitation;
- functional or anatomical pulmonary atresia;
- circular shunting;
- severe cardiomegaly;
- and cardiovascular collapse.
For some of these infants, attempting immediate conventional biventricular repair is inappropriate.
A different strategy may be required. (PubMed Central (PMC))
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The Starnes Procedure
The Starnes procedure is a palliative operation developed for critically ill neonates with severe Ebstein Anomaly.
The principle is to exclude the dysfunctional right ventricle and move the circulation towards a single-ventricle pathway.
A fenestrated patch is used to close the tricuspid valve orifice.
This stops severe regurgitant flow into the massively abnormal right ventricle.
Pulmonary blood flow is then supplied separately, commonly using a systemic-to-pulmonary shunt.
The patient can subsequently progress towards:
Glenn
and, where appropriate,
Fontan palliation. (PubMed Central (PMC))
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Is Starnes Always Permanent?
Historically, a Starnes procedure generally committed the child to single-ventricle palliation.
That concept is evolving.
Contemporary centres have reported selected children undergoing later cone repair after initial Starnes palliation, permitting conversion towards a two-ventricle or one-and-a-half ventricle circulation. (PubMed)
This illustrates how modern congenital cardiac surgery increasingly treats surgical pathways as adaptable rather than necessarily irreversible from the first operation.
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Biventricular Neonatal Repair
Selected neonates with adequate right ventricular and valve anatomy may undergo early biventricular repair.
Various techniques have been described.
However, severely unstable neonates remain among the most challenging patients in congenital cardiac surgery.
Current expert consensus emphasises careful risk stratification rather than applying one operation to every severe neonatal case. (PubMed)
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Anaesthetic and Theatre Considerations
Ebstein Anomaly creates several unusual anaesthetic problems.
Important considerations include:
- severity of tricuspid regurgitation;
- right ventricular function;
- pulmonary vascular resistance;
- atrial-level shunting;
- cyanosis;
- ductal physiology;
- arrhythmias;
- and cardiomegaly.
In severe disease, raising pulmonary vascular resistance can significantly reduce forward pulmonary blood flow.
Factors that may increase PVR include:
- hypoxia;
- hypercarbia;
- acidosis;
- hypothermia;
- and excessive airway pressure.
Arrhythmias can also cause sudden haemodynamic deterioration.
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The Problem of Positive-Pressure Ventilation
Severe cardiomegaly may compress the lungs.
The infant may require ventilatory support.
However, excessive intrathoracic pressure can reduce systemic venous return and make right-sided haemodynamics worse.
Ventilation therefore needs to balance adequate oxygenation and CO₂ clearance against preservation of venous return and pulmonary blood flow.
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Cardiopulmonary Bypass
Definitive valve repair generally requires cardiopulmonary bypass.
Surgery may involve:
- cone reconstruction;
- atrial reduction;
- reduction of the atrialised ventricle;
- ASD closure or fenestration;
- arrhythmia surgery;
- and occasionally a Glenn connection.
For critically ill neonatal palliation, the operative strategy may instead focus on excluding the right ventricle and establishing stable pulmonary blood flow.
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After Repair
Important postoperative considerations include:
- residual tricuspid regurgitation;
- right ventricular function;
- low cardiac output;
- pulmonary blood flow;
- atrial shunting;
- arrhythmias;
- and conduction abnormalities.
The right ventricle may require time to adapt to its reconstructed geometry and workload.
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Long-Term Follow-Up
Ebstein Anomaly requires lifelong congenital cardiac surveillance.
Potential long-term problems include:
- recurrent tricuspid regurgitation;
- right ventricular dysfunction;
- progressive right-sided dilation;
- atrial arrhythmias;
- accessory-pathway tachycardias;
- cyanosis;
- heart failure;
- and need for repeat valve intervention.
Patients who undergo childhood treatment should therefore transition to adult congenital cardiology rather than routine adult cardiac follow-up alone. (www.heart.org)
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Ebstein Anomaly in One Sentence
Ebstein Anomaly is a congenital malformation in which the tricuspid valve is displaced into the right ventricle, creating atrialisation of part of the ventricle, tricuspid regurgitation and variable impairment of forward pulmonary blood flow.
The two most important questions are:
How much functional right ventricle remains?
and
Can that ventricle provide adequate pulmonary blood flow?
The answers largely determine whether the patient is an asymptomatic adult, a cyanosed child, or a critically ill blue neonate.
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Key Points
Ebstein Anomaly primarily affects the tricuspid valve and right ventricle.
The septal and posterior tricuspid valve leaflets are displaced towards the ventricular apex.
Part of the anatomical right ventricle becomes atrialised.
Tricuspid regurgitation can be severe. (www.heart.org)
An ASD or PFO commonly allows right-to-left shunting and cyanosis.
Severe neonatal disease can produce functional pulmonary atresia.
A patent ductus may either support pulmonary blood flow or, in certain circumstances, contribute to a dangerous circular shunt. (PubMed)
Ebstein Anomaly has an important association with accessory conduction pathways and WPW syndrome. (www.heart.org)
The cone repair is an important modern reconstructive operation for suitable patients.
A one-and-a-half ventricle repair can combine tricuspid valve reconstruction with a Bidirectional Glenn.
The Starnes procedure provides single-ventricle palliation for selected critically ill neonates. (PubMed Central (PMC))
Patients require lifelong congenital cardiac follow-up.
Glossary of Terms
Accessory Pathway
An abnormal electrical connection between the atria and ventricles that bypasses the usual conduction route.
Accessory pathways are particularly associated with Ebstein Anomaly.
Atrialisation
Functional incorporation of part of the anatomical right ventricle into the right atrial chamber because the tricuspid valve is displaced towards the ventricular apex.
Atrial Septal Defect — ASD
An abnormal communication between the atria.
In Ebstein Anomaly it may permit right-to-left shunting and cause cyanosis.
Bidirectional Glenn
A surgical connection between the Superior Vena Cava and pulmonary arteries.
It can be used as part of a one-and-a-half ventricle repair or single-ventricle palliation.
Cardiomegaly
Abnormal enlargement of the cardiac silhouette.
Severe Ebstein Anomaly can produce extreme cardiomegaly because of right atrial dilation.
Circular Shunt
A pathological circulation in which blood repeatedly travels around an ineffective loop through the heart, pulmonary artery, ductus and systemic circulation without producing useful forward output.
It can occur in severe neonatal Ebstein Anomaly.
Cone Repair
A tricuspid valve reconstruction technique in which available leaflet tissue is mobilised and rotated to create a cone-shaped valve at the true tricuspid annulus.
Cyanosis
Bluish discoloration resulting from increased quantities of deoxygenated haemoglobin in systemic arterial blood.
Ebstein Anomaly
A congenital malformation characterised by apical displacement and abnormal development of the tricuspid valve, atrialisation of part of the right ventricle and variable right ventricular dysfunction.
Functional Pulmonary Atresia
Absence of effective forward flow through an anatomically patent pulmonary valve because the right ventricle cannot generate adequate forward pressure.
One-and-a-Half Ventricle Repair
A circulation in which the right ventricle continues to provide some pulmonary blood flow while a Bidirectional Glenn directs SVC blood directly into the pulmonary arteries.
Patent Foramen Ovale — PFO
Persistence of the foetal atrial communication after birth.
Pulmonary Vascular Resistance — PVR
Resistance encountered by blood moving through the pulmonary circulation.
Reduction Atrioplasty
Surgical reduction in the size of an excessively enlarged atrium.
Right-to-Left Shunt
Movement of deoxygenated blood from the right side of the circulation into the systemic arterial circulation.
Starnes Procedure
A palliative operation for severe neonatal Ebstein Anomaly involving exclusion of the dysfunctional right ventricle and establishment of pulmonary blood flow, traditionally as the first stage of a single-ventricle pathway.
Supraventricular Tachycardia — SVT
A rapid heart rhythm originating above the ventricles.
SVT is particularly associated with accessory conduction pathways in Ebstein Anomaly.
Tricuspid Regurgitation
Backward flow of blood through the tricuspid valve during ventricular contraction.
Tricuspid Valve
The valve normally separating the right atrium from the right ventricle.
Wolff–Parkinson–White Syndrome — WPW
A pre-excitation syndrome caused by an accessory electrical pathway between atrium and ventricle.
It is more common in patients with Ebstein Anomaly.
