Ebstein's anomaly--an autopsy study of 28 cases.CV Madiwale, JR Deshpande, SG Kinare
Department of Pathology, Seth G.S. Medical College, Parel, Mumbai.
Twenty eight autopsy specimens of Ebstein's anomaly were studied in order to evaluate the morphologic features of the abnormal tricuspid valve. All cases showed marked dilatation of the original tricuspid annulus, a normally positioned anterior leaflet and variable downward displacement of the posterior and septal leaflets. Sixteen cases showed a very large anterior leaflet. All three leaflets showed dysplastic features and a wide range of anatomic abnormalities in the valve and valve apparatus. A thin walled atrialised right ventricle was present in nine cases. Associated cardiac anomalies were seen in 21 cases, the commonest being an atrial septal defect (17 cases).
Keywords: Adolescent, Adult, Autopsy, Child, Child, Preschool, Ebstein′s Anomaly, complications,pathology,Female, Heart Defects, Congenital, complications,Heart Septum, pathology,Heart Ventricle, pathology,Human, Infant, Male, Middle Age, Tricuspid Valve, pathology,
Ebsteinís anomaly is a rare disorder with a reported incidence of 0.5% or less among patients with congenital heart disease. It is characterized by downward displacement of the posterior and septal tricuspid leaflets with a normally positioned anterior leaflet. This results in division of the right ventricle into a proximal atrialised segment with a distal sinus and outflow portion. This anomaly is known to have a wide range of pathologic features. Variations in the pathologic anatomy need to be recognized, as they would influence the surgical correction and prognosis. This study was carried out to identify the spectrum of abnormal features in Ebsteinís anomaly with special emphasis on a detailed morphologic analysis of the abnormal tricuspid valve.
Twenty-eight autopsy specimens of heart with Ebsteinís anomaly were collected over a period of 37 years at the Cardiovascular Pathology Section, King Edward Memorial Hospital. Relevant clinical details were noted and a detailed morphological study of the tricuspid valve, right ventricle and other associated anomalies was carried out. The degree of downward displacement and the size of the atrialised right ventricle were noted by measuring the distance between the original atrioventricular annulus and the point of maximal displacement of the septal and posterior leaflets. The dysplastic changes in the tricuspid valve leaflets were graded according to the pattern followed by Becker et al.
Twenty-eight cases of Ebsteinís anomaly formed 1.83% of the congenital heart disease specimens received at our centre. There were 12 males and 16 females. Twenty cases were less than 15 years of age, out of which six were less than six months old, the oldest patient was a 55 year old female.
Morphology of the Tricuspid Valve:
In all cases, there was marked dilatation of the original atrioventricular ring. The abnormal anterior leaflet had been excised in two cases and excision of the posterior and septal leaflets was performed in one other case. Valve replacement was performed in two cases and in one of these all three original leaflets had been excised. Plication of the atrialised right ventricle and annuloplasty had been performed in one case each. In all the operated cases, the degree of downward displacement could still be identified. The abnormal features noted in the anterior, posterior and septal tricuspid leaflets are summarised in [Table - 1] & [Table - 2].
The anterior leaflet showed no displacement from the atrioventricular annulus, but its morphology was normal in only two cases. Grade 2 dysplasia was frequently noted. Sixteen cases had a large, curtain like anterior leaflet [Figure - 1] and in three of these the leaflets were thin and membranous. Thickening of the leaflet was noted in three cases, while in two cases there were numerous fenestrations. In three cases the anterior leaflet was plastered to the underlying myocardium [Figure - 1] with total absence of the chordae and papillary muscles in two of these. Of the latter two cases, one had a partial atrioventricular defect and in the other case, a small opening between the anterior and septal leaflets was the only outlet for the blood flow. Chordae were totally absent in three other cases and the leaflet was directly attached to the papillary muscle in two cases or the right ventricle in one case. In 12 cases, the chordae were abnormal, being few, thick and short [Figure - 2]. Abnormal insertion of the chordae in the right ventricular outflow, just below the pulmonary annulus was seen in one case [Figure - 3]. In six cases, the anterior papillary muscle was a thin, ill formed muscular structure, supporting a large sail like anterior leaflet. In two cases, the anterior papillary muscle was represented by a broad flat band [Figure - 2] and in two other cases, it was just a muscular ridge.
Septal and Posterior Leaflets:
The septal and posterior valve structures are considered together as both showed variable degrees of downward displacement. In four cases, the posterior leaflet showed greater displacement as compared to the septal leaflet. Two types of displacement, partial and complete, were noted.
1.Partial Displacement (2 cases):
In one case each, the septal and posterior leaflet showed normal annular attachment. The septal leaflet with normal annular attachment was adherent to the right ventricular myocardium and this was consistent with Grade 3 dysplasia. When the posterior leaflet showed normal annular attachment, it showed features of Grade I dysplasia.
2. Total Displacement(26 cases):
The prominent dysplastic features noted in these cases were abnormal chordae that were thin, delicate and ill formed (14 cases) [Figure - 4], absence of chordae (6 cases) [Figure - 5], abnormal poorly developed papillary muscle (6 cases) and absence of papillary muscles (6 cases). In the absence of chordae and papillary muscles, the valve tissue was plastered to the right ventricular myocardium (8 cases) [Figure - 1]. Focal agenesis of the septal leaflet was noted in one case and in another, the posterior leaflet was replaced by irregular nodular tissue with absence of chordae [Figure - 6]. All the above features would fall into the category of Grade 2 and 3 dysplasia. Grade 1 dysplasia showing irregular thickening of the valve leaflets but normal chordae and papillary muscles was seen in only one case.
The Right Ventricle:
In all cases, the size of the atrialised right ventricle was inversely proportional to the size of the right ventricular sinus [Figure - 1]. However, there was no co-relation between the size of the atrialised right ventricle and the grade of tricuspid valve dysplasia. In nine cases, the atrialised right ventricle was thin walled and in three of these, it was aneurysmally dilated, forming a posterior bulge. Abnormal trabecular pattern of the right ventricular sinus was seen in nine cases. There was no significant obstruction of the right ventricular outflow tract though in one case, there was abnormal insertion of the anterior leaflet chordae [Figure - 3].
Left side of the Heart:
A frequent finding was myxomatous changes in the mitral valve leaflets (6 cases) and a small left ventricular cavity (11 cases).
These were seen in a total of 21 cases, eight of which showed more than one associated cardiac abnormality.
Ebsteinís anomaly of the tricuspid valve is an uncommon developmental abnormality with a reported incidence of less than 1% of all congenital cardiac malformations,. The natural history of this disease is variable,, and it is believed that early death is often related to diagnostic procedures or thoracotomy which are poorly tolerated by these children. Most of our cases were less than 15 years but none of their deaths were related to any diagnostic procedure. Majority of our patients had congestive heart failure due to severe tricuspid deformity.
Though the classical definition of Ebsteinís anomaly emphasizes the downward displacement of a part or all of the tricuspid ring and valve, we have in addition, noted a wide range of abnormal features. One of our most constant findings was dilatation of the right atrioventricular junction. Anderson and Lie have emphasized this feature and believe it to be due to lack of support during embryologic development. Another feature was the dysplasia of the tricuspid valve leaflets which was noted in almost all our cases. We believe that dysplasia of valve leaflets is an inherent part of Ebsteinís anomaly and this has been stressed by others as well. Becker et al observed that dysplasia of the tricuspid valve may occur as an isolated lesion or is seen with corrected transposition and Ebsteinís anomaly. The dysplastic changes seen in our cases were not just restricted to the displaced septal and posterior leaflets, but were a conspicuous feature in the anterior leaflet as well. More than half our cases showed a large curtain like anterior leaflet. Though this feature has not been included in the grading of dysplasia as described by Becker, it should necessarily be included in the category of dysplastic valves.
The indications for surgical treatment of Ebsteinís malformation are not clearly defined and the ideal surgical mode of management remains controversial,,,. Our study emphasizes that dysplasia of all three tricuspid valve leaflets is a consistent finding in this condition. The dysplastic leaflets and the dilated atrioventricular ring would both contribute significantly to the malfunctioning of the tricuspid valve and resultant cardiac failure. In this setting, a valve replacement with plication of the thin walled atrialised right ventricle could possibly be the preferable mode of surgical treatment,,. However, because of the wide spectrum of anatomic variations in the tricuspid valve, the surgical approach to patients with Ebsteinís anomaly needs to be individualised according to the specific morphology found at operation. As seen in our series, Ebsteinís malformation is often associated with other cardiac anomalies and this should also be considered before surgical correction of the defective tricuspid valve is attempted.
[Figure - 1], [Figure - 2], [Figure - 3], [Figure - 4], [Figure - 5], [Figure - 6][Table - 1], [Table - 2], [Table - 3]