Ebstein's anomaly is a rare disorder accounting for approximately 1% of all congenital heart diseases.1) The morphologic defect of Ebstein's anomaly involves the failure of delamination of the tricuspid valve (TV) leaflets, resulting in a wide variety of abnormalities; adherence of the leaflets to the underlying myocardium, apical and posterior displacement of the dilated TV annulus, dilation of the "atrialized" portion of the right ventricle, fenestrations, redundancy, and tethering of the anterior leaflet.2) In addition, associated cardiac malformations are common. An interatrial communication was reported in 80 to 94% of patients, and other additional associated anomalies included bicuspid or atretic aortic valves, pulmonary atresia or hypoplastic pulmonary artery, subaortic stenosis, coarctation, mitral valve prolapse, accessory mitral valve tissue or muscle bands of the left ventricle, ventricular septal defects, and pulmonary stenosis.3) Patients with Ebstein's anomaly also frequently show arrhythmias. Right bundle branch block is one of the common electrocardiographic features.4) There is also an increased incidence of accessory conduction pathways, and these contribute to the development of supraventricular and ventricular tachyarrhythmias.5)6) Clinical symptoms of patients with Ebstein's anomaly are mainly related to cyanosis, right-sided heart failure, and arrhythmias.7) A wide spectrum of symptoms has been described due to the complexity of abnormalities in the anomaly. In 1988, Carpentier and associates classified Ebstein's anomaly according to the degree of leaflet tethering, degree of apical displacement and degree of dilatation of the atrialized right ventricle.8) A variety of surgical methods were introduced in treatment of Ebstein's anomaly. Those treatments included a TV repair or replacement for the principle element in the treatment of Ebstein's anomaly and additional concomitant procedures for the correction of comorbid anomalies (such as ablation of accessory conduction pathways, resection or plication of the atrialized right ventricle, application of bidirectional cavo-pulmonary shunt, and single-ventricle repair for advanced right ventricular dysfunction).9)

The aim of the study was to evaluate the long-term results after a surgical repair of Ebstein's anomaly during the past 30 years.

The study protocol was reviewed by the Institutional Review Board and approved as a minimal risk retrospective study (Approval Number: H-1510-032-710) that did not require individual consent based on the institutional guidelines for waiving consent.

Of 8045 patients who underwent open heart surgery between 1982 and 2013 at Seoul National University Children's Hospital, 48 patients had been diagnosed with Ebstein's anomaly (48/8045, 0.6 %).

The diagnosis of Ebstein's anomaly was based on echocardiography in all patients. Those patients with pulmonary atresia with intact ventricular septum, complex conotruncal abnormalities, and atrioventricular discordance with ventriculoarterial discordance ("corrected transposition") were excluded from the study.

Of 48 patients, 28 patients (58.3%) were female and had a median age of 5.6 years (1 day-42.1 years) at the time the operation was performed; 2 patients were neonates (4.2%), 8 were infants (16.7%), 33 were children (68.8%), and 5 were adults (10.4%). Major preoperative symptoms of the patients were exertional dyspnea (n=24, 50%) and cyanosis (n=24, 50%). Most common associated cardiac anomalies was atrial septal defect (n=40, 83.3%). Arrhythmias were presented in 25 patients (52.1%) preoperatively, and right bundle branch block (n=15, 31.3%) was the most common. Forty-five patients (93.7%) demonstrated tricuspid regurgitation (TR) of greater than moderate degree. When the patients were divided according to Carpentier's classification, types A, B, C, and D were 11 (22.9%), 21 (43.8%), 12 (25.0%), and 4 (8.3%) patients, respectively (Table 1).

The present study revealed 3 main findings. First, Ebstein's anomaly is a rare surgical disorder accounting for approximately 0.6% of all congenital open heart surgery patients at Seoul National University Children's Hospital. Second, surgical treatment strategies in Ebstein's anomaly are decided according to Carpentier's types. Third, survival and freedom from reoperation rates at 10 years were 95.8% and 68.0%, respectively, and approximately 25% patients needed a eredo operation for tricuspid valve during the follow-up.

Ebstein's anomaly is a complex congenital disorder, which encompasses a large spectrum of diseases involving tricuspid valves as well as right ventricular function, and has a prevalence of approximately 1% of all congenital heart diseases.1) One recent study on the Society of Thoracic Surgeons Congenital Heart Surgery Database (STS-CHSD)10) demonstrated low average annual institutional case volumes (median, 1 per year) and high in-hospital mortality in neonatal patients in comparison with infants, children, and adults. In the present study, the incidence of Ebstein's anomaly was similar to a previous report, with 0.6% of all congenital open heart diseases operated at our institution. The goals of surgical treatment of Ebstein's anomaly includes correction of tricuspid valve regurgitation, restoration of right ventricular dysfunction, and treatment of other comorbid cardiac conditions such as arrhythmias. The surgical treatment of Ebstein's anomaly has continually evolved since the initial report of repositioning of the septal and posterior leaflets by Hunter and Lillehei in 1958.11) Hardy and colleagues introduced a technique of plication of an atrialized ventricle.12) Danielson and colleagues modified Hardy's method, which became one of the most frequently used methods in the treatment of Ebstein's anomaly.13) Danielson's technique included transverse plication of the atrialized right ventricle, resulting in a tricuspid valve formed by a single leaflet coapted to the interventricular septum. In 1988, Carpentier et al. reported a new technique with longitudinal plication of the right ventricle and mobilization and repositioning of the tricuspid valve.8) In 1989, da Silva and colleagues developed a new surgical technique called cone reconstruction of the tricuspid valve, aiming at the reconstruction of a valve similar to a normal one.14) Although tricuspid valve repair is preferable to replacement, tricuspid valve replacement is considered when repair is not feasible. In addition, bidirectional cavopulmonary shunt or "one-and-a-half ventricle repair" is performed when the functional capacity of the right ventricle is insufficient to unload right ventricle.15)16) In the present study, a bidirectional cavopulmonary shunt was performed if the patient's right atrial pressure was higher than 15 mmHg after cardiopulmonary bypass weaning.

If patients had severe right ventricular dysfunction, single ventricle repair or Fontan procedures may be the treatment of choice.17) The variety of surgical techniques in treating Ebstein's anomaly represents the enormous anatomic variability that exists. In this study, tricuspid valve replacement rather than repair was performed at the earliest period. Thereafter, tricuspid valve repair using Danielson's technique had been performed. Since 2000, tricuspid valve repair using Carpentier's technique was performed, and since 2013 the Cone repair has been performed. Survival or freedom from reoperation was not statistically related to the types of repair such as bi-ventricular repair versus one-and-a half ventricular repair versus single ventricle palliation. The types of repair were significantly related with Carpentier's type and the patient's age at operation. Single ventricle repair was done in patients with a more progressed disease such as Carpentier's types C and D, or in neonatal patients. Patients who had a more progressed disease or who required surgical correction during the neonatal period probably had a more severe form RV dysfunction; a single ventricle palliation or one-and-a-half ventricular repair was preferred to biventricular repair.

After surgical treatment of Ebstein's anomaly, the severity of TR was significantly decreased in all patients. It tended to progress thereafter, however, and freedom from recurrent TR rates at 5, 10, and 15 years were 88.6%, 66.3%, and 52.7%, respectively. There was no significant difference in the recurrence rate of TR according to surgical strategies although the follow-up duration after cone repair was relatively short and patients who underwent cone repair were relatively small in number. Hence, further follow-up is warranted in order to evaluate differences according to surgical strategies; those who underwent follow-up examinations including chest X-rays and echocardiograms. Because progressive dilatation of the right ventricle and recurrent TR were major concerns for long-term follow up care of patients, a better assessment of TR severity could help with the appropriate selection of patients who would benefit from a subsequent TV repair or replacement.18) Advances in evaluation technologies such as tissue Doppler imaging, speckle tracking echocardiography, and cardiac magnetic resonance imaging were proposed for a better assessment of RV function.19)

One previous study demonstrated that greater severity of Ebstein's anomaly, cardiothoracic ratio of >60%, RVOT obstruction, and presentation as a fetus were associated with poorer survival.20) Another study demonstrated that early age at presentation, hepatomegaly, need for mechanical ventilation and medication, and associated cardiac abnormalities were strongly associated with death.21) However, those results were obtained by analyzing patients who had not been operated on. In the previous study analyzing patients who underwent surgical correction for Ebstein's anomaly, no risk factors were identified for late mortality after surgery.22) In the present study, no statistically significant risk factors of death and reoperation were found. These findings, however, might be related to the small number of patients enrolled in the study.

One of the major comorbidities of Ebstein's anomaly is arrhythmia. One previous study showed that arrhythmia associated with Ebstein's anomaly substantially improved after conservative surgical intervention.23) On the contrary, another study demonstrated that concomitant antiarrhythmic procedures resulted in excellent freedom from recurrence of arrhythmias.24) In the present study, all the patients revealed normal sinus rhythm at the last follow-up, suggesting that the result of resolution of arrhythmia was excellent after surgical repair of Ebstein's anomaly, with or without concomitant anti-arrhythmic procedures. Therefore, further studies are warranted in order to reveal the efficacy of concomitant antiarrythmic procedures.

The present study showed that survival rates at 5, 10, and 20 years after surgery for Ebstein's anomaly were 95.8%, 95.8%, and 85.6%, respectively, and freedom from reoperation rates for 5, 10, and 15 years were 85.9%, 68.0%, and 55.8%, respectively. These results were similar to previous studies demonstrating the survival and freedom from reoperation rates.22)25)

There are limitations of the study that must be recognized. First, the study was a retrospective study. Second, relatively small patients were included in the study, although we collected data of more than 30 years. Third, patients included in the study had heterogenous characteristics and various surgical strategies in the treatment of Ebstein's anomaly.

In conclusion, surgical treatment of Ebstein's anomaly showed favorable long-term results despite anatomic and clinical complexities. Further follow-up is warranted in order to evaluate differences according to surgical strategy.