Ebstein's anomaly

Background

Ebstein anomaly is a rare congenital heart disease (CHD). It involves a malformation of the tricuspid valve (TV) and the right ventricle (RV). The anomaly occurs in approximately 1 per 200,000 live births and accounts for less than 1% of all congenital heart defects. Its spectrum of anatomical variations and severity is wide, ranging from severe neonatal forms to less symptomatic cases diagnosed in adulthood.

Ebstein anomaly is characterized by apical displacement of the tricuspid valve leaflets (primarily the septal and posterior leaflets) into the right ventricle, resulting in a malformed tricuspid valve, an atrialized portion of the right ventricle, and a small functional right ventricle. This anomaly often includes tricuspid regurgitation (TR), right atrial enlargement, and, in severe cases, associated defects like atrial septal defect (ASD) or patent foramen ovale (PFO). In neonates, severe forms can present with cyanosis/hypoxia, or hemodynamic instability, particularly when complicated by circular shunt physiology. 

The key pathophysiological feature of Ebstein’s anomaly is the incomplete separation (failure of delamination) of the tricuspid valve leaflets from the interventricular septum during fetal development. The condition most often involves the septal and posterior leaflets, which are displaced apically, resulting in downward displacement of the tricuspid annulus and an anterior-apical shift of the tricuspid orifice. In some descriptions, this has also been characterized as a rotational movement of the valve leaflets toward the right ventricular outflow tract. Displacement is typically defined as a downward shift of the septal leaflet by more than 8 mm/m² relative to the anatomic tricuspid annulus. The anterior tricuspid leaflet is frequently abnormal, with unusual chordal attachments, and may become hypermobile, producing a “sail-like” appearance. In contrast, it can also be tethered, limiting its mobility, and in some cases fenestrations are present. The right ventricle is divided into two distinct portions: the atrialized RV and the functional RV. The atrialized portion corresponds to the area between the normally placed annulus and the functional chamber, which receives the regurgitant jet from tricuspid insufficiency and dilates along with the right atrium. The functional portion of the RV may be greatly reduced in size; in severe cases, it may consist largely of the outflow tract due to significant apical displacement of the septal and posterior leaflets.

A failure of delamination refers to an abnormal developmental process where the tricuspid valve leaflets—particularly the septal and posterior (or inferior) leaflets—do not properly separate from the underlying right ventricular myocardium during embryogenesis. Normally, delamination allows the valve leaflets to become mobile and functional. When this process fails: 

• The leaflets remain adhered to the ventricular wall. 

• This leads to inferior displacement of the valve hinge points into the right ventricle. 

• The result is a dysfunctional valve and an atrialized portion of the right ventricle, contributing to tricuspid regurgitation and right heart dilation.

Circular shunting is a unique and critical phenomenon in some neonates with Ebstein anomaly, where blood flows in a cyclical, non-productive loop between the right heart, lungs, and left heart without effective systemic or pulmonary circulation. This occurs primarily in the presence of severe tricuspid regurgitation, a right-to-left inter-atrial shunt, right left to right patent ductus arteriosus, elevated pulmonary vascular resistance (PVR) favouring blood from from the PDA to reach the main pulmonary artery, and significant pulmonary insufficiency leading to MPA-RV flow. 

Ebstein's anomaly has been associated with maternal lithium use during pregnancy, although most cases are sporadic. It is characterized by various degree of displacement of the tricuspid valve towards the apex of the RV, with the posterior and septal leaflets being displaced.  This leads to "atrialization" of the RV segment included in the right atrium, with subsequent enlargement of the RA and decreased RV functional cavity. Ebstein's anomaly is associated with atrial septal defect, Wolff-Parkinson-White (and supra-ventricular tachycardia) and risk of strokes. Often, these patients present with an enlarged cardiac silhouette on chest radiography (“Wall to Wall" heart).

Severe Ebstein's can be associated with the "Circular shunt physiology" (or "Circle of death"), a flow physiology by which blood flow goes from Right to Left atrium (via the ASD/inter-atrial shunt), to the Left ventricle, to the Aorta, to the Pulmonary artery (by the PDA) to the right ventricle (by pulmonary insufficiency), to the right atrium (via the tricuspid regurgitation), to the left atrium by the ASD.

Circular shunt physiology in Ebstein: 

Aorta → Ductus → Pulmonary artery → Pulmonary Insufficiency → Right Ventricle → Tricuspid insufficiency → Right atrium → Foramen Ovale → Left atrium → Mitral valve → Left ventricle → Aortic valve → Aorta → Ductus arteriosus (Learn more here, and here). It refers to a recirculating loop of blood that bypasses systemic perfusion, often involving the right atrium, right ventricle, pulmonary arteries, ductus arteriosus, aorta, and back into the right heart—creating a futile circulatory loop. In Ebstein anomaly, the tricuspid valve is displaced apically, leading to a massive right atrium and an often severely dysfunctional or hypoplastic right ventricle. This causes severe tricuspid regurgitation, elevated right atrial pressure, and ineffective forward flow into the pulmonary artery. The functional pulmonary atresia seen in severe cases occurs because the RV cannot generate enough pressure to open the pulmonary valve. Some have described the use of maternal NSAIDs as a way to constrict the fetal duct in an attempt to address this fatal physiology for the fetus / newborn. Article here on "Surgical Management of Neonatal Ebstein’s Anomaly Associated With Circular Shunt".

Effective pulmonary blood flow is significantly reduced due to the following mechanisms: 

1. Low right ventricular (RV) output, resulting from decreased RV capacitance caused by atrialization of the RV. 

2. Severe pulmonary valve insufficiency, which leads to regurgitation and further reduces forward flow. 

As a result, the pulmonary artery (PA) is underfilled, and the ductus arteriosus (PDA) provides flow to the PA via a left-to-right shunt. However, this flow comes at the expense of systemic perfusion, effectively “stealing” blood from the systemic circulation. The PDA jet is directed toward the incompetent pulmonary valve, allowing blood to flow retrogradely from the PDA into the PA and back into the RV. Pulmonary vascular resistance (PVR) is typically elevated due to low pulmonary blood flow, which triggers reflex vasoconstriction in an attempt to preserve perfusion pressure. Additionally, hypoxemia and acidosis, which are often present, further raise PVR. This hemodynamic environment favors the abnormal circuit of flow: from the PDA to the PA, through the insufficient pulmonary valve, and into the RV. Some of the treatment strategies may involve: pulmonary vascular relaxation (iNO, oxygen exposure, titrated mechanical ventilation), restriction of the duct to break the circular shunt (NSAIDs or ligation), supporting the cardiac function in the context of acidosis, hypoxemia and likely low coronary perfusion pressure (high RA pressure in which the coronary sinus drains), while avoiding too much increase in PVR or SVR. As such, many of those infants require some low dose epinephrine, or milrinone (if the BP is not low). 

More on Ebstein's anomaly by clicking here (outside article).

More on fetal Ebstein and circular shunt physiology here.

Diagrams by CHD Doodles (Yaeji Kim)

Echocardiographic Example 1

Echocardiographic Example 2

Branch pulmonary arteries which are hypoplastic, fed by the left to right PDA.

Echocardiography Example 3 - Ebstein's Anomaly with Pulmonary Valve Insufficiency

The patient was born following an uneventful pregnancy in an outborn setting and was referred to our center for cardiac management. Delivery was via cesarean section for maternal indications, and no resuscitation was required at birth. The infant transitioned well initially. However, during skin-to-skin contact, the nursing team noted a dusky appearance. The infant was placed under a warmer, and oxygen saturation was found to be 70%. Despite administration of 100% oxygen, the maximum pre- and post-ductal saturations reached only 85%. There were no signs of respiratory distress, but CPAP was trialed without improvement. Physical examination revealed normal heart sounds (S1 and S2) with a prominent holosystolic and diastolic murmur, described as to-and-through. The infant was alert and breathing comfortably, with no signs of increased work of breathing. Perfusion was adequate, with brisk capillary refill (<2 seconds) and strong peripheral and femoral pulses. The liver was palpable 1–2 cm below the costal margin. No dysmorphic features were noted. Chest radiography showed cardiomegaly. Blood gas analysis revealed a pH of 7.3, pCO₂ of 38, and lactate of 1.4. The infant had voided. Prostaglandin E1 (PGE) was initiated, and the infant was transferred to our center. Given the relative clinical stability and the markedly enlarged cardiac silhouette, Ebstein anomaly was the leading differential diagnosis, particularly in light of the murmur, which is consistent with significant tricuspid regurgitation and possible pulmonary insufficiency. Other considerations included cyanotic congenital heart disease with right ventricular outflow tract obstruction and ductal-dependent pulmonary blood flow, or antenatal ductal closure—though the latter typically presents with more severe instability. Mixing lesions such as truncus arteriosus were also considered, but the prominent cardiomegaly favored Ebstein anomaly. Blood pressure at the time of the echocardiography was 56/42 (mean 46). 

Subcostal View

PDA view

Here the PDA is large on PGE and is completely left to right - from the aorta to the pulmonary artery. In this particular patient, the PDA is supporting pulmonary blood flow int he context of the low RV output. 

Unrestrictive left to right large PDA. The CW-Doppler outlies the low velocity through the PDA, with no degree of restriction to flow and pressure transmission. By definition, the PA pressure is the same as the one with the Aorta by pressure equalization. The directionality of the duct indicates the PVR < SVR. 

Parasternal Views

The branch pulmonary arteries are of good size. The flow through the PAs is fed via the ductus. 

Apical Views

Here we can appreciate from the anterior sweep that the pulmonary valve does not open during the cardiac cycle. By colour, we can see the pulmonary insufficiency throughout the cardiac cycle. The CW-Doppler is outlined. There is a peak systolic velocity measured. This only informs on the

Suprasternal Views