Ebstein’s malformation of the tricuspid valve

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Pathophysiology

Ebstein’s malformation is a rare congenital anomaly characterized by downward displacement of the posterior and septal leaflets of the tricuspid valve, combined with an enlarged sail-like anterior leaflet. The portion of the right ventricle on the atrial side of the inferiorly displaced tricuspid valve is abnormally thinned. This thinning is known as “atrialization.” Anatomic severity of the Ebstein’s tricuspid valve, right atrium, and right ventricle is variable. Commonly, the tricuspid valve is insufficient and the right atrium is dilated. Tricuspid insufficiency is occasionally combined with stenosis. Right ventricular and right atrial dysfunction results in cyanosis and right ventricular failure. Surgical intervention is undertaken when symptoms develop.

Neonatal presentation of Ebstein’s malformation represents a difficult and unique challenge. The neonate with Ebstein’s malformation presents with cyanosis due to right ventricular dysfunction. Patency of the ductus arteriosus is usually required to provide adequate pulmonary blood flow. The pulmonary valve, although normally formed, does not open due to the inability of the Ebstein’s right ventricle to generate pressure in excess of the pulmonary artery pressure. Systemic venous return crosses an atrial septal defect and mixes with pulmonary venous return, resulting in cyanosis.

Surgical technique

The ideal surgical approach to repair of Ebstein’s malformation of the tricuspid valve is to create a normally functioning tricuspid valve and close any atrial communication, resulting in separation of the pulmonary and systemic circulations. Various surgical repair techniques have been performed for post-natal presentation of Ebstein’s malformation. The atrialized portion of the right ventricle is plicated, the tricuspid valve and/or annulus is reconstructed, and the atrial septal defect is closed. In addition, redundant atrial wall is usually resected prior to atriotomy closure.

Surgical approach to repair of Ebstein’s malformation presenting during the neonatal period is individualized, but an innovative approach to severe forms of this anomaly has been described by Starns et al. This approach, like the others described above, requires

cardiopulmonary bypass and aortic cross-clamping. The tricuspid valve orifice is closed using a patch of cryopreserved homograft, pericardium, or synthetic material. Care is taken when placing sutures near the coronary sinus ostium since atrioventricular conduction pathways are located in this area. Unrestricted flow across the atrial septal defect is ensured by resecting the atrial septum. Next, the redundant atrialized right ventricular tissue can be plicated and the dilated atrial wall resected. The patent ductus arteriosus is divided, and pulmonary blood flow is provided by placement of a systemic to pulmonary artery shunt. Cardiopulmonary bypass time and aortic cross-clamp time required to complete repair are usually moderate. Subsequent surgical intervention would include bidirectional cavopulmonary shunting and eventually, Fontan completion.

Postoperative considerations

The postoperative course following neonatal palliation of Ebstein’s malformation can be variable. Invasive monitors used include arterial and central venous catheters. Atrial lines are used when needed for access and/or hemodynamic management. Measurement of preload to the ventricle allows for titration of volume replacement and adjustment of vasoactive infusions. Non-invasive monitors include NIRS (near infrared spectroscopy) probes to assess adequacy of regional and global perfusion and traditional pulse oximetry. Vasoactive agents might include epinephrine and/or milrinone. Numerous other agents are available and are tailored to the specific needs of the patient, targeting adequate oxygen delivery to the tissues of the body and optimization of cardiac output.

Arrhythmia is a common complication encountered in patients with Ebstein’s malformation. Preoperative atrial and ventricular dilatation, as well as right ventricular dysfunction, predispose these patients to arrhythmias. In addition, the surgical repair requires placement of sutures near atrioventricular conduction pathways. Atrioventricular pacing equipment should be readily available. Bleeding is an uncommon complication. Following acute recovery, the usual neonatal postoperative course would apply. Hospital stay required following repair averages 2 to 3 weeks.