Ebstein Anomaly

Ebstein anomaly is a very rare congenital heart lesion representing <1% of all CHD. It is a complex condition involving failure of tricuspid valve lea et delamination during embryogenesis. It represents a broad continuum of morphologic derangements but the central de ning feature is apical displacement of the septal lea et of the tricuspid valve, usually associated with severe TR. Even though the septal lea et tends to be the most involved, usually all 3 lea ets are involved to a certain extent, with the anterior lea et being the least involved. e lea ets tend to be dysplastic, muscularized, and tethered to short chords and papillary muscles that may insert directly into the lea ets. e valve is spirally rotated with the septal and posterior lea ets displaced inferiorly into the RV. is in turn displaces the functional annulus of the valve downward, leaving a variable portion of RV on the atrial side of the valve lea ets (“atrialized” portion of the RV). e atrialized portion of the RV tends to be thin and dyskinetic, and is usually signi cantly dilated due to the degree of TR. is also leads to signi cant dilation of the true annulus of the tricuspid valve.

Ebstein anomaly is a very rare congenital heart lesion representing < % of all CHD. It is a complex condition involving failure of tricuspid valve lea et delamination during embryogenesis. It represents a broad continuum of morphologic derangements but the central de ning feature is apical displacement of the septal lea et of the tricuspid valve, usually associated with severe TR. Even though the septal lea et tends to be the most involved, usually all lea ets are involved to a certain extent, with the anterior lea et being the least involved. e lea ets tend to be dysplastic, muscularized, and tethered to short chords and papillary muscles that may insert directly into the lea ets. e valve is spirally rotated with the septal and posterior lea ets displaced inferiorly into the RV. is in turn displaces the functional annulus of the valve downward, leaving a variable portion of RV on the atrial side of the valve lea ets ("atrialized" portion of the RV). e atrialized portion of the RV tends to be thin and dyskinetic, and is usually signi cantly dilated due to the degree of TR. is also leads to signi cant dilation of the true annulus of the tricuspid valve.

Pathophysiology and Clinical Presentation
In Ebstein anomaly, the degree of prograde ow across the RV is limited due to the severe TR and variable impairment of RV function. In addition, the atrialized portion of the RV tends to distend during atrial contraction, further limiting prograde ow. All of these structural abnormalities lead to massive right-heart dilation. Massive right-heart dilation can lead to in utero underdevelopment of the lungs due to lack of physical space. Patients with Ebstein anomaly will usually have an ASD that tends to shunt right to left, causing variable degrees of cyanosis. e clinical presentation varies signi cantly depending on the degree of TR, degree of RA dilation, extent of atrialization of the RV, RV function, and degree of pulmonary hypoplasia. It can vary from cardiogenic shock in the neonate to an asymptomatic presentation in adulthood.
In neonates, the high PVR and the presence of a ductus arteriosus lead to a higher afterload of the RV, further limiting prograde ow. As such, neonates tend to present with variable degrees of cyanosis and heart failure.
Patients with less severe forms of the disease, or those who survive the neonatal period without intervention, may present later in life with cyanosis, decreased exercise tolerance, dyspnea on exertion, or palpitations due to arrhythmias. A systolic murmur in the left sternal border is usually heard, and there is wide splitting of the rst and second heart sounds. ere may be IJ distention.
Children and adults with Ebstein anomaly are at signi cant risk for atrial tachyarrhythmias (atrial ectopic tachycardia and atrial utter) due to RA dilation. In addition, -% of patients have accessory pathways along the tricuspid valve annulus that can lead to reentrant supraventricular tachycardia.  • CXR ( Figure -). Severe cardiomegaly due to the severe TR and RA dilation is the pathognomonic nding on Ebstein anomaly. ere are cardiac lesions that present with such a signi cant degree of cardiomegaly: Ebstein anomaly, dilated cardiomyopathy, and a large pericardial e usion. e amount of visible lung may be signi cantly limited due to the degree of cardiomegaly and pulmonary hypoplasia. • Echocardiography. Main diagnostic modality. e formal de nition of Ebstein anomaly is apical displacement of the septal lea et of the tricuspid valve > mm/m ( Figure -). e displacement is measured compared to the level of attachment of the mitral valve annulus and indexed to BSA. It is important to de ne the degree of TR and the extent of atrialization of the RV ( Figure -). In neonates, it is imperative to evaluate the pulmonary valve for patency, since a closed pulmonary valve may be anatomically atretic or functionally atretic ( Figure -). Pulmonary valve patency may be predicted by observing PI but the lack of PI does not necessarily indicate anatomic pulmonary atresia. In newborns with a large PDA, there may not be prograde ow across the RVOT due to severe TR (retrograde ow) and elevated PVR. • Cardiac MRI. It has become a useful adjunct in the management of older patients in recent years. It allows further assessment of RV and LV size and function. .

Figure -.
Side-by-side -chamber color-compare views of Ebstein anomaly with significant apical displacement of the septal leaflet of the tricuspid valve and severe TR. Image courtesy of Dr. Josh Kailin, www.pedecho.org.

Figure -.
Side-by-side subcostal color-compare views of flow through the PDA and then retrograde through the pulmonary valve. This patient had functional pulmonary valve atresia due to the lack of prograde flow across the pulmonary valve, but not anatomic or true atresia, as noted by the presence of PI. .

Preoperative Management
Initial treatment of critical newborns with functional pulmonary valve atresia is aimed at decreasing PVR with ventilation, oxygenation, and iNO. Patients require sedation and possibly neuromuscular blockade to further decrease PVR. Afterload reduction can be added if the BP is adequate to promote systemic blood ow. In patients with poor cardiac output, inotropes may need to be initiated with the known increased risk of tachyarrhythmias in these patients. In such individuals (who typically have been started on PGE at birth in the setting of a fetal diagnosis), the decision to attempt PGE weaning can be very challenging. e key question is whether the RV can generate enough force to overcome the PVR and manage the degree of TR. In many patients, it is very important for the management team to be persistent in these e orts: many patients can ultimately be weaned from PGE after failing initial attempts (and thereby avoid newborn surgery). A unique situation in neonates occurs in the presence of signi cant PI. e presence of a PDA in this setting allows blood to ow through the PDA, retrograde through the incompetent pulmonary valve, then retrograde through the insu cient tricuspid valve to the RA and across the ASD (right-to-left shunting), through the left heart out to the aorta, and the back through the PDA. is "circular shunt" (Figure -) can compromise both systemic and pulmonary blood ow. In these profoundly cyanotic patients, starting prostaglandins may be detrimental. e same circular shunt can occur if the pulmonary valve is atretic and is ballooned open, leading to PI.
Care of a neonate with severe Ebstein anomaly can also be complicated by lung hypoplasia due to limited in utero development. Inability to ventilate due to severe lung hypoplasia can impact survivability in these patients. Decisions to proceed with surgical intervention or possibly extracorporeal support need to take into consideration the degree of pulmonary hypoplasia. In these challenging situations, CT of the lungs may be helpful in delineating the degree of parenchymal immaturity.

Indications / Timing for Intervention
In the neonatal period, initial evaluation of oxygen saturations and cardiac output determine if any intervention is needed. Most children with Ebstein anomaly will ultimately achieve a balanced circulation with adequate systemic oxygen saturation. As per above, persistent attempts at medical management are warranted unless the infant is critically unstable. If neonates present with high PVR, a circular shunt, and compromised cardiac output, interventions are aimed at ventilating and decreasing PVR to reverse the retrograde ow through the pulmonary valve. e decision to intervene is often based on response to these therapies.
In patients with true (anatomic) pulmonary atresia, there will be a need to establish a source of pulmonary blood ow. is is best accomplished after the PVR has dropped, and can be in the form of a modi ed Blalock-Taussig-omas shunt (mBTTS) or a ductal stent (see Chapter ) with or without dilation of the pulmonary valve depending on echocardiographic size. In neonates with a diminutive RV, consideration should be made of a Starnes procedure (see below). If there is a sizeable RV but the child cannot maintain a good cardiac output due to the amount of TR, consideration can be made of attempting to repair the tricuspid valve. Tricuspid valve repair is also a consideration in older children with heart failure symptomatology due to severe TR (see below).

Anesthetic Considerations
Anesthetic considerations should re ect careful assessment of the patient's current status and ongoing management. A controlled, careful induction with IV narcotic and benzodiazepine can be supplemented with anesthetic vapor to minimize rapid changes in physiology. iNO, inotropes, and vasopressors should be available if not already initiated. Given the proclivity of children with Ebstein anomaly to develop tachyarrhythmias, this is one situation for which de brillation pads may be helpful even with a rst-time sternotomy.
In critical newborns presenting with low cardiac output and marginal systemic arterial oxygen saturations, anesthetic management is focused on optimizing ventilation and maintaining cardiac output. ese babies may be very unstable during transport and anesthesia induction. As such, it is critical to have all members of the surgical and OR team in attendance at induction.

Surgical Intervention
Timing of surgical intervention and mode of operative correction has evolved signicantly over the past decades as surgical techniques have improved. e primary goal of surgery for Ebstein anomaly is to improve right-heart e ectiveness in generating prograde PA ow through tricuspid valve repair, reduction/elimination of nonfunctional portions of the RV (atrialized portion), partial or complete ASD closure, and where necessary, pulmonary valve replacement.
As discussed previously, newborns with symptomatic Ebstein present a challenging surgical problem and historically, operations on these babies have been associated with signi cant risk of mortality. e primary decision in newborns is whether or not to attempt tricuspid valve repair. In those individuals in whom the valve is deemed irreparable, RV exclusion through patch closure of the tricuspid ori ce ("Starnes" operation) may be the only viable option. When this is done, it is imperative to fenestrate the patch such that the RV is able to decompress into the RA. e operation also includes an atrial septectomy and creation of an mBTTS.
Several investigators have documented encouraging results with tricuspid valve repairs in newborns, but these results are not widely consistent in the greater congenital heart surgery community. In repairing the tricuspid valve in small babies, the operation is made all the more challenging by the very delicate nature of tricuspid valve tissue in these children. As such, it has been our approach that if possible, interim palliation is o ered such that tricuspid repair is o ered later in childhood when the valve tissue is more substantial.
In older children and adults, the "Cone" operation as initially described and implemented by Da Silva has revolutionized surgical repair of Ebstein anomaly. e core principle of the Cone operation is to mobilize all available tricuspid valve tissue (including the portion that is not fully delaminated from the RV free wall) from its abnormal attachements, leaving only the apical support intact. e valve is separated from the abnormal tricuspid annulus, rotated in a clockwise direction and then a "cone" of valve tissue is created by suturing all the valve tissue together. e conceptual understanding of this operation is greatly facilitated by thinking of the reconstructed cone like a sort of long Hemlich valve. Once the cone is reconstructed, the atrialized portion of the RV is plicated longitudinally to create a more e cient RV cavity and to construct a new tricuspid annulus that is normally positioned. e cone is then reattached at the level of the new annulus with great care to avoid the AV node. Most surgeons then add a formal annuloplasty ring. Following reconstruction of the tricuspid valve, the ASD is either partially or completely closed, depending on the e ectiveness of the reconstruction and the size of the tricuspid inlet. In patients where we are concerned about the repair, we will typically leave a fenestration in the atrial septum ( -mm). If there is concern that the tricuspid ori ce is too small, we will add a bidirectional Glenn shunt to augment pulmonary blood ow and o oad the RA.
In desperate situations where there has been a failed attempt at tricuspid repair, it may be necessary to replace the tricuspid valve. Of course, this is a problematic solution in that all available tissue prostheses will eventually degenerate and have to be replaced. is degeneration is notoriously more rapid in children. It is also critical to make every e ort to prevent surgical AV block in tricuspid valve replacements and in patients where there is de cient tissue in the region of the true annulus near the AV node. As such, the prosthesis is placed well up into the body of the RA, leaving the coronary sinus below the sewing ring of the prosthesis. In recent years, with the advent of transcatheter valve replacement alternatives, the option of "valve-in-valve" replacement of degenerated prostheses may be considered.

Postoperative Management
Postoperative management is dependent on the intervention undertaken. In neonates, much of the postoperative management involves dealing with the rami cations of preoperative instability, elevated PVR, and pulmonary hypoplasia/ventilator concerns. Sedation is imperative to managing these critically ill neonates. At times, they may also require neuromuscular blockade in the initial postoperative days. In neonates who undergo an mBTTS or ductal stent, management is aimed at balancing Qp:Qs, which can be uid as PVR drops (see Chapter ). In those that undergo a Starnes procedure, in addition to managing Qp:Qs, there are the usual considerations involved in managing a neonate who has undergone CPB and cross-clamping, with the IV uid, inotrope, and in ammatory considerations that this entails. Patients who undergo a tricuspid valve repair in the neonatal period will have similar considerations and will bene t from further attempts to decrease PVR and maintain cardiac output. Consideration of the patient's risk of tachyarrhythmias is important as many children have accessory pathways and irritable atria due to dilation and suture lines that lead to a higher risk of this complication. Inotropes may need to be tailored to avoid increasing arrhythmia burden by decreasing adrenergic agents.
For older patients, early extubation (ideally intraoperative) following repair mitigates the deleterious e ects of positive-pressure ventilation. Inotropic support should be tailored to reduce PVR and minimize the tendency for atrial tachycardia.

Long-Term Management
Patients can remain asymptomatic if the degree of TR is mild and there is limited atrialization of the RV. Tachyarrhthymias can be the presenting sign leading to diagnosis in older children with less hemodynamically signi cant lesions.
All patients with Ebstein anomaly should be assessed for the presence of an accessory AV conduction pathway and it is preferred that such pathways be ablated in the electrophysiology lab prior to surgical intervention. In those rare individuals with persistent accessory pathways after attempted catheter ablation, surgical division of the pathway should be performed at the time of the tricuspid valve repair operation. In addition to tachyarrhthmias, patients with Ebstein anomaly can have progressive heart failure symptomatology due to the degree of TR. In addition to right-sided heart failure symptomatology, they can also develop LV failure due to poor interventricular interactions and septal shift secondary to right-sided volume overload. Much of the long-term care in patients with Ebstein anomaly is determined by their initial course and required surgical interventions.