Ebstein Anomaly




Abstract


Ebstein anomaly is a rare congenital disorder of the tricuspid valve and right ventricular myocardium. The presentation depends on the severity of the disorder and can range from severe cyanosis and heart failure in the newborn to mild exercise intolerance in the adult. The pathologic hallmark is the downward and apical displacement of the tricuspid valve into the right ventricle. Echocardiogram usually provides sufficient anatomic and hemodynamic information. Medical management depends on the degree of hemodynamic stability and centers around supplemental oxygen and prostaglandin infusion. Those who respond to medical measures should be watched over a period of time. Surgical intervention is needed when patients fail to respond to standard medical resuscitative measures. Techniques of surgical repair have evolved over a period of time. Most techniques are based on plication of the redundant atrialized right ventricle, tricuspid annuloplasty, use of the sail-like anterior leaflet in construction of a competent monocuspid valve, closure of atrial septal defect, and reduction of right atrium. Single-ventricle palliation has been advocated by some groups. We are heavily biased toward a biventricular repair. We describe our approach, surgical technique, and postoperative results here. Multicenter studies are needed to establish the best modalities for surgical management.




Key Words

Ebstein, Tricuspid, Ventricle, Cyanosis, Surgery

 


Ebstein anomaly (EA) is a rare cardiac disease and accounts for less than 1% of all newly diagnosed congenital disorders. EA is not just a disorder of the tricuspid valve (TV) but also affects the right ventricle (RV) myocardium. It encompasses a wide anatomic spectrum, and the disorder can present itself either as cyanosis in the newborn or exercise intolerance in the older adult. Symptomatic neonates present serious medical and surgical challenges and have uniformly dismal outcomes without timely intervention.




Pathologic Anatomy


It is worth recapitulating the characteristic features of this disorder that are relevant to surgical management as described by Carpentier et al.



  • 1.

    There is a failure of delamination of the TV leaflets. The septal, posterior, and anterior leaflets are affected in order of severity. This effectively causes anterior and apical rotational displacement of the functional annulus. The downward displacement of the septal and posterior leaflets into the RV is the essence of EA.


  • 2.

    The anterior leaflet is attached at the appropriate level but is large or sail-like. There are multiple chordal attachments to the ventricular wall. In neonates presenting with symptoms the anterior leaflet is often severely affected.


  • 3.

    The portion of the RV above the functional annulus (“atrialized right ventricle”) is dilated and thin with variable hypertrophy. The true tricuspid annulus is almost always enlarged.


  • 4.

    The cavity of the effective RV is reduced (“functional right ventricle”).


  • 5.

    The infundibulum of the RV is often obstructed by the redundant tissue of the anterior leaflet and its chordal attachments to the infundibulum.



As mentioned earlier, EA is truly a disorder of both TV and RV. There is a variable degree of ventricular myocardial dysfunction. Morphometric histopathologic studies have demonstrated that there is an absolute decrease in the number of myocardial fibers in addition to thinning of the wall of the dilated RV in EA.


Carpentier et al. also described four grades of EA.




  • Type A : The anterior leaflet has normal morphology, and the RV is adequate.



  • Type B : The anterior leaflet has abnormal chordae but normal mobility. The RV is reduced in volume but adequate.



  • Type C : The anterior leaflet is restricted in movement. The RV is small with a large atrialized component.



  • Type D : This is also called “tricuspide sac” because the leaflets form a complete sac of fibrous tissue adherent to the RV. The only functional part of the RV is the infundibulum.





Associated Anomalies


Cardiac




  • 1.

    An atrial septal defect (ASD) is present in most of the cases.


  • 2.

    There is a variable degree of RV outflow tract obstruction, and anatomic pulmonary atresia occurs in approximately half of the symptomatic neonates requiring surgical intervention.


  • 3.

    A patent ductus arteriosus (PDA) is present in EA with pulmonary atresia.


  • 4.

    Wolff-Parkinson-White type of accessory pathway is present in approximately 10% of the cases.


  • 5.

    Rarer associations include ventricular septal defect, transposition of great arteries, tetralogy of Fallot, and atrioventricular canal defect.



Noncardiac


Low-set ears, micrognathia, cleft lip and palate, absent left kidney, megacolon, undescended testes, and bilateral inguinal hernias are commonly associated anomalies.




Pathophysiology


The pathophysiology and clinical presentation vary depending on the anatomic severity of the disorder. In fact there is a high rate of fetal demise for this disorder. At its extreme end (type C and D) there is severe displacement of the TV, leading to an ineffective RV and severe valve regurgitation. This results in severe cardiomegaly with consequent lung hypoplasia and cyanosis because most of the systemic venous return is shunted across the ASD. Persistent elevation in pulmonary vascular resistance (PVR) is a major impediment to successful antegrade ejection from the smaller and less effective RV. The pulmonary blood flow is hence dependent upon the PDA because there is no effective flow generated by the small RV (physiologic pulmonary atresia). Often there can be true right ventricular outflow tract obstruction (anatomic pulmonary atresia). The left ventricle is often pancaked by the enlarged RV. When the disease is less severe (type A and B), the RV can establish effective antegrade flow as PVR decreases, and this is accompanied by clinical improvement in symptoms. Neonates with severe tricuspid regurgitation (TR) or gross cardiomegaly who are otherwise asymptomatic have an associated mortality of 45% within the first year of life without intervention. The natural history of EA during infancy is thus gloomy. However, those who survive early childhood can expect reasonable longevity. When the disease is mild, symptoms are not noticed until later in adult life. Symptoms are often related to exercise intolerance from progressive TR.




Diagnostic Studies


Chest X-Ray Examination


Results of the chest x-ray examination of a symptomatic EA patient are characteristic. There is significant cardiomegaly (box-like heart) with the cardiac silhouette almost filling the entire chest. It is not uncommon to have a cardiothoracic ratio of 1 on the chest x-ray examination results in a neonate presenting with severe symptoms.


Electrocardiogram


Results of electrocardiography are abnormal in most patients. Tall and broad P waves, bizarre morphologies of terminal QRS pattern, and first-degree heart block are all common. Between 6% and 36% have accessory pathways, with most of them located around the orifice of the malformed TV.


Echocardiogram


This is confirmatory and provides sufficient anatomic and hemodynamic information. The principal echocardiographic characteristic that differentiates EA from other forms of congenital TR is the degree of apical displacement of the septal leaflet at the crux of the heart. The echocardiogram also provides information on the degree of atrialization of the RV, size of the tricuspid annulus, severity of the TR, and degree of pulmonary stenosis. It may be difficult to differentiate physiologic from anatomic pulmonary atresia.


GOSE Scoring System


First reported by Celermajer et al. from the United Kingdom, the Great Ormond Street Echocardiogram (GOSE) score has important prognostic value in stratifying risk of death and is based on the calculated ratio of the sum of the right atrium and atrialized RV areas to the sum of the remaining chambers derived from a four-chamber view on echocardiography ( Fig. 64.1 and Table 64.1 ).




Figure 64.1


Great Ormond Street Echocardiogram (GOSE) score. aRV, Atrialized right ventricle; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.


TABLE 64.1

Mortality Risk by GOSE Score
























GOSE Score Ratio Mortality (%)
1-2 <1.0 8
3 (acyanotic) 1.1-1.4 10 early, 45 late
3 (cyanotic) 1.1-1.4 100
4 >1.5 100

GOSE 1 <0.5; GOSE 2 >0.5 and <1.0; GOSE 3 >1.0 and <1.5; GOSE 4 >1.5.

GOSE, Great Ormond Street Echocardiogram.


Cardiac Catheterization


A cardiac catheterization is unnecessary and often triggers fatal arrhythmias. The right ventricular and pulmonary pressures are usually normal, although the right ventricular end-diastolic pressure may be abnormal.




Treatment


Medical


Medical treatment of the symptomatic neonate depends on the degree of hemodynamic stability. Patients who are reasonably stable are treated with supplemental oxygen and prostaglandin infusion and closely observed for adequacy of cardiac output and oxygen saturations. Treatment of unstable patients involves intubation, deep sedation (fentanyl, 2 to 4 mcg/kg/h) and paralysis in addition to initiation of prostaglandins. Ventilation should be adjusted to decrease PVR. We use large tidal volumes (12 to 15 mL/kg) to offset the effects of gross cardiomegaly on lung expansion. Inhaled nitric oxide may be invaluable in reducing PVR. A continuous infusion of bicarbonates and inotropes (usually dopamine, 5 to 10 mcg/kg/h) may be necessary. Following a confirmation of diagnosis by echocardiogram, the clinical progress should be monitored closely. Daily echocardiograms are obtained, looking specifically for enhanced antegrade pulmonary blood flow. In our own experience, as well as others’ experience, approximately half the neonates tend to stabilize and improve over a few days as PVR decreases. Serial echocardiograms will document increasing pulmonary blood flow. Prostaglandin infusion and ventilation are weaned gradually as tolerated.




Surgical


Indications for Surgery


Neonates who continue to decline in spite of standard resuscitative measures need surgical intervention because death is certain ( Fig. 64.2 ). Those who respond to medical measures should be watched over a period of days to weeks. Prostaglandin should be weaned gradually as PVR drops and antegrade pulmonary blood flow increases. The child may be able to establish adequate RV output to be extubated and discharged home. If, however, the child does not tolerate weaning of prostaglandin (oxygen saturation below 80%) or positive pressure ventilation, surgical intervention will become necessary. Those with anatomic pulmonary atresia will necessarily require surgery (see Fig. 64.3 ). Generally if the GOSE score is 3 or 4, the patients will require some form of surgical intervention in the neonatal period. It is also worth noting that among those who somewhat respond to medical intervention the predominant symptom of right heart failure is difficulty in tolerating feedings secondary to mesenteric venous congestion.


Jun 15, 2019 | Posted by in CARDIOLOGY | Comments Off on Ebstein Anomaly
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