Kimberly A. Holst and Joseph A. Dearani Department of Cardiovascular Surgery, Mayo Clinic, Rochester, MN, USA Ebstein malformation is a rare congenital heart lesion comprising approximately 1% of all congenital heart disease, with an estimated population incidence of approximately 1 in 20,000 live births [1]. Dr. Wilhelm Ebstein, a young Polish physician, described the cardiac findings of a 19‐year‐old man who had died of cyanotic heart disease in 1866 [2]. Ebstein described the characteristic anatomic findings in this anomaly, as well as the hemodynamic abnormalities, and correctly correlated them with the patient’s signs and symptoms. Ebstein malformation is an exceptionally heterogeneous disease with varied patient presentation; symptomatic neonates are often critically ill, while others with less severe presentations may be asymptomatic into adulthood [3]. Left‐sided Ebstein malformation in congenitally corrected transposition of the great arteries will be discussed in Chapter 26. The initial description of the lesion we now describe as Ebstein malformation, with exquisite illustrations prepared by Dr. Weiss (Figure 29.1) [4], was based upon the anatomic findings relating to the heart of Joseph Prescher, a 19‐year‐old laborer with cyanosis, who had been troubled with dyspnea and palpitations since childhood [2]. The premortem diagnosis had been “congenital cardiac defect.” Figure 29.1 shows the salient features of the lesion, namely that the tricuspid valve, guarding the right atrioventricular junction, closes in bifoliate rather than trifoliate fashion. Not all cases, however, are directly comparable to the illustration provided by Dr. Weiss. Understanding the malformed anatomy depends on an appreciation of how the abnormal development affects the three leaflets of the tricuspid valve. Thus, although the essential feature is displacement of the hinge point of the tricuspid valve leaflets away from their expected position at the atrioventricular junction, the three leaflets are not affected in uniform fashion. Indeed, it is very unusual for the extensive antero‐superior leaflet to have any of its hinge displaced from the atrioventricular junction, although this can occur on rare occasions (Figure 29.2). Figure 29.1 The heart of Joseph Prescher as seen from the ventricular aspect, as illustrated for Wilhelm Ebstein by Dr. Weiss. The leaflets of the deformed valve close in bifoliate fashion, forming a keyhole orifice that opens toward the infundibulum of the right ventricle. Source: Reproduced by permission from O’Leary PW et al. In: Paediatric Cardiology, 3rd ed. Philadelphia, PA: Churchill Livingstone/Elsevier; 2010, pp. 713–730. Figure 29.2 The specimen, from a typical case of Ebstein malformation, has been opened through the inferior aspect of the right atrioventricular junction. It is photographed obliquely from the right side looking anteriorly. Although part of the antero‐superior leaflet retains its hinge (red dots) at the atrioventricular junction, the lateral part is displaced (yellow dots) within the ventricle as part of the extensive rotational and apical displacement of the septal and inferior leaflets (green dotted line) away from the atrioventricular junction (red dashed line). It is also the case that some hearts can be encountered in the autopsy room, when it is only the hinge of the septal leaflet that is attached away from the atrioventricular junction (Figure 29.3). In those patients coming to clinical attention, and deemed suitable for surgical treatment, the entirety of the tricuspid valvar apparatus is likely to be malformed, and obviously so. In almost all such patients, nonetheless, it is only the septal and mural leaflets that have their annular attachment displaced from the atrioventricular junction, with sparing of the proximal attachment of the antero‐superior leaflet. In this respect, the septal leaflet is the most posterior leaflet of the normal tricuspid valve when viewed in attitudinally appropriate fashion, with the so‐called posterior leaflet being located inferiorly and murally. There is then another problem posed to the morphologist when analyzing these patients coming to clinical attention, since it is difficult to precisely distinguish, in the abnormal valve, the boundaries between the mural and antero‐superior leaflets. As shown by Dr. Weiss’s drawing, the end product is usually that the leaflets adopt a bifoliate configuration, with a plane of closure at the junction of the inlet and the remaining components of the right ventricle (Figure 29.4). Figure 29.3 In this heart, which has also been opened through the inferior aspect of the right atrioventricular junction, as with the heart shown in Figure 29.2, it is only the hinge of the septal leaflet of the tricuspid valve (green dotted line) that is displaced away from the atrioventricular junction (red dashed line). The hinge of the antero‐superior leaflet is marked with red dots. The appreciation of this abnormal position and structure of the valve is the key to subsequent analysis, and arguably to selection of appropriate treatment. The abnormal location represents a rotational deformity [5], rather than the “downward displacement” that tended to be the focus of previous analysis, particularly that provided by the echocardiographer (Figure 29.5). There is, however, marked variation from patient to patient. This reflects the degree of formation of the septal leaflet, and the nature of the distal attachments of the antero‐superior and mural leaflets [6]. The septal leaflet is either represented by an array of verrucous remnants adherent to the septum, is part of a tongue that becomes continuous with the antero‐superior leaflet (Figure 29.5), or persists as a circular remnant on the septum. In all these circumstances, the septal leaflet may seem to be absent when attention is directed to the ventricular inlet component (Figure 29.6). Figure 29.4 The image in the left‐hand panel, viewed from the atrial aspect, shows how, when the tricuspid valve is deformed, the antero‐superior leaflet retains its normal attachment at the atrioventricular junction (red dotted line), but the conjoined septal and mural leaflets have their hinge points attached well away from the atrioventricular junction (compare red dashed and green dotted lines). The right‐hand panel shows the ventricular aspect. The red dotted line shows the keyhole orifice of the malformed valve. Note the similarity to the drawing by Dr. Weiss (Figure 29.1). Figure 29.5 The view of the atrial aspect of a typically deformed valve shows the rotational displacement of the hinges of the septal and mural leaflets (dotted line) away from the atrioventricular junction (dashed line). There is a connecting tongue with the antero‐superior leaflet, which retains its normal attachment at the atrioventricular junction. Assessment of the abnormal valve, therefore, should be directed at the junction between the inlet component and the functional right ventricle. It is at this location that the leaflets typically form the bifoliate mechanism of closure (Figures 29.1 and 29.4). Figure 29.6 In this specimen, prepared by simulating the four‐chamber echocardiographic section, the atrioventricular junction is essentially unguarded, since the abnormal valvar leaflets have been rotated toward the ventricular apex. In the light of this location of the abnormal valvar leaflets, it follows that the functional part of the right ventricle is made up of the apical trabecular and outlet components. The antero‐superior leaflet typically retains its normal hinge from the atrioventricular junction along the supraventricular crest. When seen in the postmortem room, this arrangement can give the impression of forming a potentially competent valve. In other cases, nonetheless, the valvar mechanism is clearly seen to be incompetent and, relative to the mass of the atrialized right ventricle, is frequently judged to be stenotic. The latter arrangement is usually associated with dilation of the right atrium and the right ventricular inlet, the latter feature described as atrialization. Electrically, nevertheless, because the junction remains at its normal site, ventricular potentials will be recorded from the atrialized myocardium. Further variation is then seen in the nature of the distal attachments of the mural and antero‐superior components of the valvar curtain, which are almost always additionally dysplastic. In some cases, the antero‐superior leaflet can retain its focal attachment to the medial and anterior papillary muscles. In the most florid cases, in contrast, the entire leading edge of the antero‐superior leaflet is attached linearly to a muscular shelf formed between the inlet and apical trabecular components of the ventricle (Figure 29.7). Between these extremes are found hearts in which the edge of the leaflet is attached in hyphenated fashion along the muscular shelf. Further abnormal tethering can be found between the ventricular aspect of the abnormal leaflets and the parietal ventricular wall. Such tethering serves to constrain still further the motion of the abnormal sail produced by the combined mural and antero‐superior leaflets. Should the leaflets fuse along the edges of the keyhole, the result is tricuspid atresia in the setting of Ebstein malformation. Figure 29.7 In this example of Ebstein malformation, as in the heart shown in Figure 29.4, the antero‐superior leaflet and the connecting tongue with the septal leaflet have a linear attachment at the ventricular apex. The abnormal valve still closes in bifoliate fashion, with the “keyhole” orifice pointing toward the right ventricular infundibulum (yellow dotted line). Although the annular attachments of the abnormal leaflets of the valve are displaced from the atrioventricular junction, the triangle of Koch continues to be the landmark for the atrial components of the atrioventricular conduction tissue axis [7]. The frequent presence of accessory muscular pathways across the atrioventricular junctions results in a high incidence of pre‐excitation, this feature being found in up to one‐fourth of patients. The accessory pathways are often multiple, and are usually found to the right of the inferior paraseptal space, or in the parietal part of the junction [8]. Although the phenotype of the lesion depends on the abnormal morphology of the tricuspid valve, the leaflets of the mitral valve are frequently nodular and thickened, and prolapse is common. Associated cardiac defects are also common. Almost all patients have a coexisting interatrial communication at the oval fossa, usually a patent foramen. A large spectrum of other lesions has been described, including ventricular septal defects, atrioventricular septal defects, tetralogy of Fallot, coarctation of the aorta, and persistent patency of the arterial duct. The most common associated defect, nonetheless, is pulmonary stenosis or atresia, which is found in up to one‐third of those presenting in infancy. In those congenital cardiac anomalies in which there is situs solitus and atrioventricular discordance with ventriculo‐arterial discordance (corrected transposition), Ebstein anomaly of the left‐sided (systemic, morphologically tricuspid) atrioventricular valve may be present. The remainder of this chapter focuses on the classic right‐sided Ebstein anomaly. Forward flow of blood through the right side of the heart is retarded due to the functional impairment of the right ventricle and the incompetence of the deformed tricuspid valve. Moreover, during contraction of the right atrium, the atrialized portion of the right ventricle distends or acts as a passive reservoir, decreasing the volume of forward right ventricular blood flow. During ventricular systole, contraction of the atrialized right ventricle creates a pressure wave that impedes venous filling of the right atrium. In the majority of cases, there is a communication between the left and right atria, either because of patency of the foramen ovale or a distinct secundum atrial septal defect (ASD). The shunt of blood through the septal opening is generally from right to left, but may be bidirectional. The overall effect of these structural abnormalities is gross dilatation of the right atrium, which may reach enormous proportions, even in infancy. This dilatation leads to further incompetence of the tricuspid valve and widening of the interatrial communication. As a consequence of atrial dilatation, atrial tachyarrhythmias are quite common, occurring in approximately 25–65% of patients [1]. Additionally, approximately 15% of patients will have one or more accessory conduction pathways, including Wolff–Parkinson–White syndrome, and 10% of patients will have atrioventricular nodal reentrant tachycardia (AVNRT). In end‐stage heart failure, ventricular arrhythmias may be present [1]. In the newborn period, any degree of tricuspid regurgitation is accentuated by the physiologically elevated pulmonary resistance. As a result, neonates with Ebstein malformation may develop severe right‐sided heart failure and cyanosis. Severe tricuspid regurgitation results in elevated right atrial pressures and may lead to profound right‐to‐left atrial shunt across the patent foramen ovale. Low cardiac output may also result from paradoxical motion of the septum or malposition of the interventricular septum because of the enlarged right ventricle. If the neonate survives this critical period, the degree of cyanosis and heart failure may diminish as pulmonary resistance decreases. Neonatal screening and fetal echocardiograms are increasingly important in both diagnosis and prognostication. Early studies have identified forward flow through the pulmonary valve as an indicator of improved neonatal outcome [9]. The largest multicenter study to date evaluating Ebstein malformation and tricuspid valve dysplasia via fetal echocardiography identified independent predictors for mortality, including gestational age of less than 32 weeks at time of diagnosis, larger tricuspid valve annulus diameter z‐score, pulmonary regurgitation, and presence of pericardial effusion [10]. In the neonatal period, decreasing pulmonary vascular resistance with pulmonary vasodilators may be helpful to unload the right ventricle, promote antegrade blood flow into the lungs, and improve right ventricular function. In some cases, a large patent arterial duct may create a circular shunt, where blood flows from the aorta into the patent arterial duct, to the right ventricle, to the right atrium, to the left atrium, and then to the left ventricle [11]. The presence of a circular shunt is associated with increased mortality [10] and, if one is present, administration of prostaglandins should be stopped to allow for ductal closure. Chest radiographs typically demonstrate profound cardiomegaly (Figure 29.8) in neonates presenting with Ebstein malformation. Figure 29.8 These two chest radiographs demonstrate the characteristic cardiac silhouette in Ebstein malformation and the extreme cardiac enlargement. (A) Neonate on the first day of life. This baby required immediate intubation, nitric oxide, and prostaglandin infusion to maintain adequate oxygenation. (B) Child aged 4 years. This child had oxygen saturations between 50% and 90%, headaches, and episodes of supraventricular tachycardia. Source: Reproduced by permission from Brown ML, Dearani JA. In: Pediatric Cardiac Surgery, 4th ed. Chichester: Wiley‐Blackwell; 2013, pp. 571–587. Echocardiography remains the standard for establishing the diagnosis (Figure 29.9). The tricuspid valve should be thoroughly assessed, and the Great Ormond Street Ebstein score (GOSE score) calculated (Table 29.1) [12, 13]. The GOSE score, as described by Celermajer [12], is the calculated ratio of the combined areas of the right atrium and atrialized right ventricle compared to the functional right ventricle, left atrial, and left ventricular areas on an echocardiogram four‐chamber view. Figure 29.9 Example of an echocardiogram (four‐chamber view, apex down) of a patient with a severe Ebstein malformation showing a grossly displaced septal leaflet (arrow). The anterior leaflet is severely tethered and nearly immobile. The functional right ventricle is small. ARV, atrialized right ventricle; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. It is important that the right ventricular outflow tract be completely visualized to ascertain whether there is “anatomic” or “functional” pulmonary atresia. Functional pulmonary atresia refers to a setting of severe tricuspid regurgitation and right ventricular dysfunction, with reduced or absent antegrade blood flow across a normal anatomic pulmonary valve. Any degree of anatomic right ventricular outflow tract obstruction (RVOTO) (infundibulum, pulmonary valve, or branch pulmonary arteries) is a risk factor for failure of biventricular repair [16] along with both early and late mortality [17]. Differentiating functional from anatomic pulmonary atresia in the neonatal period may be difficult, and the administration of nitric oxide or sildenafil at the time of echocardiography may be useful to decrease pulmonary vascular resistance, allowing forward blood flow into the lungs in cases of functional pulmonary atresia. Medical management is the goal for neonates with Ebstein malformation; however, surgery is indicated for neonates who remain in congestive heart failure or with significant cyanosis despite adequate medical therapy, when the patient cannot be weaned from the ventilator, anatomic pulmonary atresia, or dependence on prostaglandins [18]. Asymptomatic neonates with a GOSE score of 3 or 4 (Table 29.1) or symptomatic neonates with a GOSE score of 3 or 4, mild cyanosis, a cardiothoracic ratio of more than 0.80, or severe tricuspid regurgitation are best treated with an operation [19]. Approximately one‐half of neonates diagnosed in the prenatal period with Ebstein malformation require a cardiac procedure [10], the majority being a cardiac operation. There are three main treatment pathways that can be considered in the neonate: single‐ventricle repair (i.e., right ventricular exclusion technique, Starnes approach), the biventricular repair (Knott‐Craig approach), or cardiac transplantation (Figure 29.10) [18, 20–22]. Table 29.1 Celermajer index and the estimated risk of mortality. aRV, atrialized right ventricle; GOSE, Great Ormond Street Ebstein; LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. Source: Reproduced by permission from Jaquiss RD, Imamura M. Semin Thorac Cardiovasc Surg. 2007;19:258–263. Starnes pioneered the right ventricular exclusion approach (Figure 29.11) [22]. In this univentricular strategy, the tricuspid valve orifice is patched closed, the interatrial communication is enlarged, and a systemic to pulmonary artery shunt is placed [22]. This approach is particularly appealing in those patients who have anatomic RVOTO or an abnormal anterior leaflet that would preclude a successful valve repair. Right ventricular decompression of Thebesian venous drainage is facilitated by placing a small fenestration (4–5 mm punch) in the tricuspid valve patch. This also allows progressive involution of the enlarged, dysfunctional right ventricle, which is helpful in the long term while preparing for the eventual Fontan procedure. In patients who have a patent right ventricular outflow tract, a competent pulmonary valve is required to prevent blood from entering and distending the right ventricle. If an incompetent pulmonary valve is present, the main pulmonary artery should be ligated or oversewn. These maneuvers are important to avoid persistent dilatation of a poorly functioning right ventricle that can compromise and impair left (systemic) ventricular function in the eventual Fontan circulation. Right atrial reduction is routinely performed to allow space for lung development. Sano proposed a modification to the Starnes single‐ventricle approach in which total right ventricular exclusion is performed by resection of the free wall of the right ventricle, which is either closed primarily or with a polytetrafluoroethylene patch [23]. This procedure acts like a large right ventricular plication. This adaptation of the Starnes method has been shown to be useful in neonates with poor right ventricular function [24]. Biventricular repair in the neonate was described by Knott‐Craig [18, 19, 21, 25]. In this method, there is repair of the tricuspid valve and subtotal closure of the ASD. Multiple tricuspid valve repair methods have been described to improve the chance of successful valve competency and all depend on having an anterior leaflet that can be easily mobilized. The Knott‐Craig technique is generally a monocusp repair based on a satisfactory anterior leaflet (Figure 29.12) [25]. The incomplete closure of the ASD allows for right‐to‐left shunting for offloading of the right heart, which may be helpful in the early postoperative period when there is high risk of right ventricular dysfunction and elevated pulmonary vascular resistance. To reduce the heart size and allow for lung development, generous right atrial reduction is routinely performed. Late follow‐up in neonates with biventricular repair is promising; in one article late survival was 74% at 15 years [26]. Figure 29.10 This simplified algorithm provides a guideline for decision‐making with the symptomatic neonate with Ebstein malformation. A good anterior leaflet for potential monocusp repair is large, sail‐like, and mobile. AL, anterior leaflet; LV, left ventricle; PA, pulmonary arteries. Source: Reproduced by permission from Knott‐Craig CJ et al. Ann Thorac Surg. 2000;69:1505–1510. Figure 29.11 (A) In the Starnes approach to neonatal Ebstein malformation [22], fixed autologous pericardium is sewn to the anatomic annulus (at the atrioventricular groove) using a running suture. Careful examination of the surface of the right ventricular myocardium is needed to ensure no distortion of the right coronary artery. A 4 mm fenestration of the patch is performed, which allows for decompression of the right ventricle. (B) If the pulmonary valve is competent, the pulmonary artery is divided and the valve is oversewn. If the pulmonary artery is small, a single hemoclip may be applied. Pulmonary blood flow is provided by a systemic to pulmonary artery shunt. In this illustration, a 3.5 mm Gore‐Tex shunt connects the innominate artery to the right pulmonary artery. Copyright © 2009 Mayo Foundation for Medical Education and Research. Reproduced by permission. Figure 29.12 (A) In the biventricular Knott‐Craig repair [25], the tricuspid valve is repaired creating a monocusp valve. If the anterior leaflet leading edge is fused to the free wall of the right ventricle, it must be delaminated to allow for free movement of the anterior leaflet. A pledgeted suture may be placed through the mobilized dominant papillary muscle of the anterior leaflet and brought to the interventricular septum at the site of the laminated septal leaflet (Sebening stitch). This maneuver will facilitate apposition of the leading edge of the anterior leaflet to the ventricular septum or septal leaflet (if present) and may provide durability to the repair (not shown). (B) When the annulus is very dilated (>20 mm), a pledgeted suture is placed at the antero‐inferior commissure through the medial wall of the coronary sinus. This will reduce the size of the tricuspid valve annulus. (C) The tricuspid valve orifice is reduced in size and the anterior leaflet is detached from its annulus. (D) The anterior leaflet is rotated clockwise and reattached to create a monocusp repair. Plication of the atrialized right ventricle completes the tricuspid valve repair. A functional orifice of approximately 13 mm is generally considered adequate. The atrial septal defect (ASD) has been subtotally closed, leaving a 3 mm residual defect or fenestration. Copyright © 2009 Mayo Foundation for Medical Education and Research. Reproduced by permission. Systemic to pulmonary artery shunt alone, without tricuspid repair, has demonstrated good results in neonates with cyanosis resistant to prostaglandin wean without severe heart failure [27]; approximately one‐half of these patients proceed to staged palliation and eventual Fontan, and the remainder proceed to either biventricular or one‐and‐a‐half ventricle repair.
CHAPTER 29
Ebstein Malformation
Overview
Anatomy
Physiology
The neonate
Presentation and Diagnosis
Indications for Surgery
GOSE score
Index RA + aRV / RV + LA + LV
Risk of mortality [14, 15]
1
<0.5
0%
2
0.5–0.99
10%
3
1–1.49
44–100%
4
≥1.50
100%
Surgical Strategies
![Schematic illustration of (A) In the Starnes approach to neonatal Ebstein malformation [22], fixed autologous pericardium is sewn to the anatomic annulus (at the atrioventricular groove) using a running suture.](https://i0.wp.com/thoracickey.com/wp-content/uploads/2023/05/c29f011.png?w=960)
![Schematic illustration of (A) In the biventricular Knott-Craig repair [25], the tricuspid valve is repaired creating a monocusp valve.](https://i0.wp.com/thoracickey.com/wp-content/uploads/2023/05/c29f012.png?w=960)
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