Recent Surgical Outcomes of Ebstein’s Anomaly: A Focus on Changes in Outcomes Due to Cone Repair


 Background: Ebstein’s anomaly exhibits a wide variety of clinical features, and therefore, proposing a standardized treatment for it is difficult. This study was conducted to determine whether Cone repair, which has been implemented in our hospital since 2008, is more effective than conventional repair.Methods: We retrospectively analyzed the clinical information of patients with Ebstein’s anomaly who were followed-up at the hospital from 2000 to 2019. A total of 61 patients who had undergone tricuspid valve repair after 2000 were divided into the conventional and Cone repair groups and their clinical outcomes were compared.Results: Of the 170 patients, 82 (48.2%) patients received surgical treatment for the tricuspid valve, whereas 75 patients received only medical treatment. The median follow-up duration was 5.89 years. After surgery, tricuspid valve regurgitation decreased and aortic stroke volume increased in both the Cone and conventional repair groups. In the Cone repair group, no mortality and postoperative complete atrioventricular block occurred and significantly fewer cases of moderate to severe tricuspid valve regurgitation were noted after surgery compared with the conventional repair group.Conclusions: Cone repair is thought to be a method with less mortality and less occurrence of complete atrioventricular block than conventional repair.


Background
Ebstein's anomaly, a rare congenital heart disease, is characterized by the downward displacement of tricuspid valve (TV) lea ets into the right ventricle. 1,2 In addition, it is a disease that exhibits a wide variety of clinical manifestations because it is determined by various factors such as the degree of displacement of the TV, concomitant cardiac malformation, right ventricular (RV) dysfunction, arrhythmia, and left ventricular (LV) dysfunction. Although the downward displacement of the TV is commonly considered severe because the symptoms appear at a young age, the degree of RV dysfunction is severe with relatively mild symptoms in adults. Therefore, determining the optimal time for surgery remains controversial in clinical practice. Hesitation regarding the surgical treatment for Ebstein's anomaly has mainly been due to recurrent arrhythmia after surgery and the requirement for repetitive surgery. [3][4][5][6] However, with the introduction of the cone reconstruction technique in 2007 by da Silva and colleagues, 7 more anatomic repair has become possible compared with that with the previous Carpentier technique. Ebstein's anomaly repair with Cone reconstruction is being performed in our hospital since 2008, and this study was conducted to determine whether Cone reconstruction results in better clinical outcomes than conventional repair.

Study Populations
Page 3 /17 The medical records of patients diagnosed with Ebstein's anomaly who were treated and followed-up at our hospital from January 2000 to December 2019 were retrospectively analyzed for clinical information and treatment methods. Patients with Ebstein's anomaly and corrected transposition of the great arteries were excluded from the study.

Statistical Analysis and Ethics Approval
All continuous variables are expressed as means ± standard deviation. A compared mean test or the χ 2 test was performed to compare the differences in the paired variables between the Cone and conventional repair group. Statistical analyses were performed using SPSS version 18.0 for Windows (SPSS, Chicago, IL, USA). A P value of ≤ .05 was considered statistically signi cant.
The Institutional Review Board of the Sejong General Hospital approved this retrospective study and waived the requirement for informed consent (approval number: 2020).
The mean and median follow-up durations were 8.79 ± 8.26 years (range: 1 day to 33.91 years) and 5.89 years, respectively. The demographic characteristics of the patients are summarized in Table 1. A total of 144 (84.7%) patients out of 170 had New York Heart Association (NYHA) functional class I or II, indicating that relatively few patients had severe heart failure. At the rst visit, the most frequent symptoms were dyspnea on exertion, followed by palpitation and chest discomfort. The most common associated congenital heart disease was atrial septal defect (ASD) or patent foramen ovale (PFO) in 92 (54.2%) patients.  Table 2). In addition, 17 patients had Wolff-Parkinson-White (WPW) syndrome, and arrhythmias originating from the atrium were more common than those originating from the ventricle. Moreover, determining whether some kinds of arrhythmia was an electrophysiological characteristic of Ebstein's anomaly or a secondary change due to enlargement of the right atrium was di cult. Furthermore, atrial utter, atrial brillation, and sinus node dysfunction were observed.  Table 3 and Fig. 1. A total of 75 (44.1%) patients opted for only medical follow-up without surgical treatment. Seven (4.1%) patients underwent tricuspid valve replacement (TVR) with tissue valve and 3 (1.8%) underwent TVR with mechanical valve, and 13 (7.6%) patients were treated only for other associated cardiac problems without TV repair. Since 1993, no TVR surgery has been performed using a mechanical valve. Cone repair was initiated in 2008. The trend of the change in the surgical method used at the Sejong General Hospital is presented in Fig. 2.  (Table 4). Compared with the conventional repair group, the Cone repair group had signi cantly greater aortic cross clamp (ACC) time and older age at operation. We compared the data of cardiac magnetic resonance imaging (MRI) performed within 6 months before and after surgery between the groups. No signi cant difference was noted between the two groups for the MRI data. After surgery, 6 (19.4%) patients of the conventional repair group had more than moderate degree of tricuspid valve regurgitation (TR). No post-operative complete atrioventricular (AV) block or operative mortality was noted in the Cone repair group. Five of the patients who underwent cone repair required reoperation, details of which are described in Table 5.

Discussion
Ebstein's anomaly is a rare disease that exhibits a wide variety of clinical features, making it di cult for clinicians to consistently accumulate experience. [8][9][10][11] Generally, neonatal Ebstein's anomaly is known to be hemodynamically unstable, di cult for surgical correction, and associated with high mortality.
However, in the case of non-severe Ebstein's anomaly, the diagnosis is often delayed because the symptoms perceived by the patient are unclear. In fact, 42.9% of the patients visiting our hospital were diagnosed with the disease only in adulthood, of which 84.7% of the patients had NYHA functional class I or II. As such, patients' symptoms are often not severe, and as can be seen in Table 3, there have been quite a lot of cases of medical treatment rather than active surgical correction. Another big reason for encouraging the judgment of such medical support is that the experience of follow-up observation with medical support was not bad in terms of survival compared with that of various active surgical treatments (Fig. 1). Until relatively recently, there have been concerns about whether surgical correction for Ebstein's anomaly has an advantage over medical support because of the increase in mortality and morbidity due to repeated reoperations after surgical repair. Indeed, the results of our hospital as well as other centers reveal that the 10-year survival of Ebstein's anomaly is more than 90%. 5,9,12,13 Many studies have reported the excellence of cone repair, [14][15][16][17][18] however, although it is performed in our institution from 2008, only 30 operations have been performed till date. A total of 5 patients required reoperation after cone repair; however, patients who underwent cone repair from 2014 did not require a reoperation (Table 5). Therefore, it can be considered that we have overcome the initial learning period relatively quickly. Remarkably, the proportion of patients with complete AV block occurrence and those with moderate or severe TR remaining after surgery were signi cantly less in the Cone repair group than in the conventional repair group. In addition, in the case of Cone repair, no mortality was reported (Table 4). Moreover, because the age of the Cone repair group patients was signi cantly higher at surgery, it may be thought that patients with a relatively mild form of Ebstein's anomaly were included. However, cone repair was not speci cally avoided in patients of young age.
Before the start of treatment, a large number of patients (85 patients, 50%) had already experienced several types of arrhythmias (Table 2). Some patients experienced multiple types of arrhythmias. Of the patients whose arrhythmia was found before starting treatment, 27 patients did not show arrhythmias after treatment. However, among the patients whose arrhythmia was not clearly identi ed before treatment, 33 cases showed new arrhythmias after starting treatment. This suggests that the burden of arrhythmia is very high in the case of Ebstein's anomaly. 18 It is thought that arrhythmia may develop even after improving the hemodynamic state and that responding with active interest is necessary.
Studies have proved that Ebstein's anomaly is not a simple tricuspid valve abnormality and is associated with LV or left atrial dysfunction. 19,20 However, it is not easy to present standardized indicators in clinical practice. It is known than hemodynamic indicators determined by cardiac MRI can be used as relatively objective indicators because there are several limitations in evaluating RV function and TR using echocardiography. Thus, it is di cult to generalize because it was not performed in all patients, but the results of cardiac MRI performed within 6 months and after surgery were reported for 17 patients of the conventional repair group (54.8%) and 18 patients of the Cone repair group (60%). However, no statistically signi cant difference was noted between the conventional and Cone repair group. After surgery, the degree of TR signi cantly decreased in both the groups, as well as the right ventricular end diastolic volume (RVEDV), right ventricular end systolic volume (RVESV), and RV ejection fraction (EF) presented a decreasing tendency (Table 4). It seems reasonable to interpret these changes as changes associated with a decrease in TR amount rather than a signi cant decrease in RV function after surgery. In addition, postoperative aortic stroke volume (SV) increased after surgery in both the groups. This result can be interpreted as after surgery, the overall cardiac output increased. Based on these results, if no mortality is associated with surgery and the frequency of reoperation is signi cantly lower than that of TVR or conventional TV plasty, it can be expected that chronic low cardiac output can be more actively improved and chronic hepatic congestion or right heart failure can be reduced by Cone repair. In other words, if we actively advance the operation age for Ebstein's anomaly than the existing age, it can expected that the outcome of patients will be slightly improved.

Study Limitations
This was a single center study with a small number of patients. In addition, limited data were analyzed due to the retrospective nature of the study.

Conclusions
Among the surgical treatment methods for Ebstein's anomaly, TVR increases the patient's discomfort and morbidity due to repeated reoperations. However, with surgical treatment, it is possible to reduce the TR amount and increase the cardiac output. TVP with Cone repair has a lesser risk of reoperation, mortality, and complete AV block than conventional repair. The Institutional Review Board of the Sejong General Hospital approved this retrospective study and waived the requirement for informed consent (approval number: 2020).

Consent for publication
Not applicable.

Availability of supporting data
All data generated or analyzed during this study are included in this published article.

Competing interests
The authors declare that they have no competing interests.
Funding Figure 1 Initial treatment methods and clinical outcomes of 170 Ebstein's anomaly cases Comparison of survival rates according to treatment methods for Ebstein's anomaly