Ebstein anomaly

Definition

Ebstein anomaly is a malformation of the tricuspid valve characterized by its dysplasia and displacement into the right ventricular cavity. Signs of Ebstein’s anomaly include poor physical endurance, dyspnea, paroxysmal tachycardia, cyanosis, cardiomegaly, right ventricular failure, and arrhythmias. The diagnosis of Ebstein’s anomaly is confirmed by electrocardiogram, echocardiogram, phonocardiogram, radiography, probing of heart cavities, atriography. Treatment of Ebstein’s anomaly is operative, including tricuspid valve replacement, removal of the atrialized part of the right ventricle, and elimination of the interatrial communication (ASD, PDA).

General information

Ebstein’s anomaly is a congenital pathology of the tricuspid atrial-ventricular valve, accompanied by an abnormal position of the flaps, resulting in the formation of an atrialized part of the right ventricle above them, forming a single unit with the right atrium. The frequency of Ebstein’s anomaly among the various congenital heart defects is 0.5-1%. Ebstein’s anomaly is often associated with other heart defects such as atrial septal defect (ASD), patent ductus arteriosus (PDA), ventricular septal defect (VSD), pulmonary stenosis or atresia, mitral stenosis or insufficiency, and WPW syndrome.

Reasons

The formation of Ebstein’s anomaly is associated with lithium intake at the early stages of embryogenesis. Infectious diseases of the pregnant woman (scarlet fever, measles, rubella), severe somatic diseases (anemia, diabetes mellitus, thyrotoxicosis), alcohol and drugs with teratogenic effects, gestational pathology (toxicosis, threat of spontaneous miscarriage, etc.) can also lead to the occurrence of this and other heart defects.

An important role in the development of Ebstein’s anomaly plays an important role in the development of congenital heart disease – along with sporadic, there are also familial cases of the anomaly.

Classification

There are four anatomical variants (types) of Ebstein’s anomaly:

• I – the anterior leaflet of the tricuspid valve is large and mobile; the septal and posterior leaflets are absent or displaced;
• II – all three atrial-ventricular valve flaps are present, but they are relatively small and displaced toward the apex of the heart.
• III – the chords of the anterior leaflet of the tricuspid valve are shortened and limit its movement; the septal and posterior leaflets are underdeveloped and displaced.
• IV – the anterior leaflet of the tricuspid valve is deformed and displaced toward the right ventricular outflow tract; the septal leaflet is formed by fibrous tissue, and the posterior leaflet is underdeveloped or completely absent.

Features of hemodynamics in Ebstein’s anomaly

The anatomical basis of Ebstein’s anomaly is a malposition of the tricuspid valve, in which its flaps (usually posterior and septal) are deformed and displaced into the right ventricular cavity. In this case, the valve flaps are attached below the fibrous ring, sometimes at the level of the outlet of the right ventricle. Valve displacement is accompanied by right ventricular atrialization, a condition where part of the right ventricle forms a continuation and a single cavity with the right atrium.

Thus, the displacement of the flaps causes the division of the right ventricle into two functional parts: the supravalvular atrialized part, which forms a common cavity with the right atrium, and the subvalvular, which is smaller in size and functions as the right ventricle. In this case, the right atrium and the atrialized part of the right ventricle are significantly dilated, and the right ventricular cavity is reduced.

The hemodynamic abnormalities accompanying Ebstein’s anomaly depend on the degree of tricuspid insufficiency, the size of the functioning right ventricle, and the magnitude of right-to-left discharge through interatrial communications.

Electrical processes in the right atrium, which consists of two parts, are not synchronized: contraction of the right atrium proper occurs in atrial systole and contraction of the atrialized part of the right ventricle – in ventricular systole. Due to tricuspid insufficiency, venous blood regurgitation back to the right atrium occurs; right ventricular stroke volume decreases, accompanied by a decrease in pulmonary blood flow. The right atrium becomes dilated and hypertrophied, and its pressure progressively increases, causing venous-arterial shunt through the defect in the atrial septum.

Right-to-left shunting plays a dual role: on the one hand, it avoids right atrial overload and compensates for the defect; on the other hand, it contributes to the development of arterial hypoxemia.

Symptoms of Ebstein’s anomaly.

Depending on the severity of hemodynamic disorders, there are three stages of the course of Ebstein’s anomaly: 

I – asymptomatic (rare); 

II – stage of marked hemodynamic disorders (IIa – without cardiac rhythm disorders; IIb – with cardiac rhythm disorders), 

III – stage of persistent decompensation.

The most severe forms of Ebstein’s anomaly can cause intrauterine fetal death. With a favorable variant of the malformation, its course remains asymptomatic for a long time; the physical development of children corresponds to age. In typical cases, Ebstein’s anomaly manifests itself in early childhood, sometimes in the first months of life.

Clinical symptoms include diffuse cyanosis, poor exercise tolerance, cardiac pain, and palpitations. Paroxysmal supraventricular tachycardia is noted in 25-50% of patients with Ebstein’s anomaly, 14% of whom have WPW syndrome. External examination reveals changes in the terminal phalanges of the fingers in the form of “drumsticks” and nails in the form of “hourglasses,” and “heart hump.”

In Ebstein’s anomaly, right ventricular insufficiency may develop early – dyspnea, liver enlargement, swelling, and pulsation of the neck veins. Arterial hypotension is often noted. The course of Ebstein’s anomaly is steadily progressive. The cause of death in older patients is most often heart failure and severe rhythm disturbances.

Diagnosis of Ebstein’s anomaly

A cardiologist and cardiac surgeon consult patients with suspected Ebstein’s anomaly and perform ECG, chest X-ray, and echocardiography. Percussion reveals an increase in the size of the heart to the right; auscultation reveals a characteristic three—or four-cycle rhythm, systolic and diastolic murmurs to the right of the method process, and splitting of the II tones.

ECG findings include rightward deviation of the electrical axis, signs of right atrial hypertrophy and dilatation, paroxysmal ventricular extrasystole and atrial tachycardia (WPW syndrome), atrial flutter, atrial fibrillation, and complete (incomplete) right bundle branch block. 

Radiological signs favoring Ebstein’s anomaly include a sharp enlargement of the right heart, a rounded shape of the heart shadow, and increased transparency of the pulmonary fields.

Echocardiography shows downward displacement of the tricuspid valve flaps, increased size of the right atrium, delayed closure of the tricuspid valve, displacement of the flaps, presence of atrialized right ventricle, right-to-left shunting blood flow through the ASD (according to Doppler echocardiography). Fetal echocardiography performed in the prenatal period can diagnose Ebstein’s anomaly in 60% of cases.

Treatment of Ebstein’s anomaly

Drug therapy for Ebstein’s anomaly is used to treat heart failure and arrhythmias. Indications for surgical correction of Ebstein’s anomaly are the presence of complaints, circulatory insufficiency, and heart rhythm disturbances. The optimal age for surgery is 15-17 years; in case of a severe form of malformation, the intervention is carried out earlier.

Radical corrective surgery for Ebstein’s anomaly includes repair or replacement of the tricuspid valve, ASD repair, and elimination of the atrialized right ventricle. In some cases, the Fontaine operation is appropriate. Sometimes, at the first stage, a Blalock-Taussig anastomosis or bidirectional cavopulmonary anastomosis is used to increase pulmonary blood flow and reduce hypoxemia.

Additional conduction pathways in WPW syndrome are subjected to radiofrequency ablation. Pacemakers or cardioverter defibrillators are implanted to treat arrhythmias.

All these treatment options are available in more than 320 hospitals worldwide (https://doctor.global/results/diseases/ebstein-anomaly). For example, Ebstein anomaly correction can be performed in 28 clinics across Turkey for an approximate price of $17.9 K (https://doctor.global/results/asia/turkey/all-cities/all-specializations/procedures/ebstein-anomaly-correction). 

Prognosis

The natural course of Ebstein’s anomaly depends on the morphologic substrate of the malformation. In the first year of life, 6.5% of patients die of severe heart failure or ventricular fibrillation; by ten years of age, 33%, and by 30-40 years of age, 80-87%.

After surgical correction of Ebstein’s anomaly, the prognosis for life is favorable. Severe cardiomegaly and the development of postoperative arrhythmias have a negative impact on the long-term results of the intervention.