Tricuspid valve malformations are very rare. The most frequent is the anomaly described by Ebstein in 1866, which represents only 0.5% of patients with congenital heart disease. Other tricuspid valve malformations are exceptional. They include annular dilatation, papillary muscle elongation, leaflet agenesis, absence of papillary muscle, or “parachute” *
* See Glossary .
valve. Tricuspid valve malformations rarely require surgery within the first years of life. When surgery becomes necessary because of severe regurgitation and cardiac enlargement, valve reconstruction is always possible using the techniques used for similar anomalies of the mitral valve. The Ebstein’s anomaly is very different because it involves both the tricuspid valve and the right ventricle .SURGICAL ANATOMY
Ebstein’s anomaly has three characteristic features ( Fig. 24-1 ). The first feature is an abnormal tricuspid valve , comprising downward displacement of the septal and posterior leaflets ( a, b ) where they attach to the right ventricle as well as severe enlargement of the tricuspid annulus. Although normally attached to the annulus, the anterior leaflet is not normal: it is significantly enlarged with a sail-like configuration and various degrees of interchordal space obliteration, and it is attached to the ventricular wall by fibrous bands. The second characteristic feature of Ebstein’s anomaly is an atrialized portion of the right ventricle above the attachment of the displaced posterior and septal leaflets (inlet portion) ( c ). The third feature is a malformation of the right ventricle; which is markedly reduced in size beyond the tricuspid valve, does not have an inlet chamber, and may present with different degrees of reduced contractility.
Depending on the severity of the anatomical lesions, four types of Ebstein’s anomaly have been described ( Fig. 24-2 ) ( Table 24-1 ).
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Type A . The downward displacement of the septal and posterior leaflets is moderate and the leaflets have retained some mobility. The anterior leaflet is well developed. The atrialized chamber is small and contractile. There is adequate right ventricular volume.
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Type B . The downward displacement of the posterior and septal leaflets is more pronounced. The septal leaflet is hypoplastic. The atrialized chamber is large, thin, fibromuscular, and poorly contractile. The right ventricle is small with preserved contractility. The anterior leaflet is large, moves freely, and has no or limited interchordal space obliteration.
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Type C . The posterior and septal leaflets are markedly displaced downward and may be severely hypoplastic and adherent to the ventricle ( Fig. 24-3 ). The atrialized chamber is very large, with a thin, noncontractile wall and branches of the right coronary artery flowing on its epicardial surface. The functional right ventricle is very small with a severely reduced contractility (a) . The anterior leaflet, which may be partially muscular, has restricted motion resulting from interchordal space obliteration and has fibrous and/or muscular bands that attach the ventricular aspect of the valve to the ventricular wall (b) . The posterolateral and anteroseptal commissures are well delineated. The communication between the atrialized chamber and the functional right ventricle may be restrictive and often displays a severe prolapse of its anterior edge. The left ventricle is small because of the paradoxical motion of the ventricular septum.
FIGURE 24-3
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Type D . This anomaly is also named “Tricuspide sac” *
* See Glossary .
because the leaflets form a continuous sac of fibrous tissue partially adherent to the right ventricle except in the infundibular area. Communication between the fibrous sac and the infundibulum of the ventricle is achieved by a restrictive hole. The ventricular wall, to which the fibrous sac is adherent, is thin and poorly contractile. The only functional part of the right ventricle is the infundibulum.
| A | B | C | D | |
|---|---|---|---|---|
| Septal-posterior leaflet displacement | + | + + | + + + | “SAC” |
| Anterior leaflet: | ||||
| Morphology | Normal | Abnormal chordae | Partial ventricular adhesions | Extensive adhesions |
| Mobility | Normal | Normal | Restricted | Absent |
| Atrialized chamber: | ||||
| Size | Small | Large | Large | SAC |
| Contractility | Preserved | Reduced | Minimal | Absent |
| Right ventricle: | ||||
| Size | Normal | Reduced | Small | Infundibulum |
| Contractility | Preserved | Preserved or reduced | Reduced | Severely depressed |
PATHOPHYSIOLOGY
The hemodynamic consequence of Ebstein’s malformation is predominantly tricuspid regurgitation ( Fig. 24-4 ). Associated tricuspid stenosis is occasionally present. Tricuspid valve dysfunction in association with reduced right ventricular volume and opposing atrial contraction (i.e., diastolic in the atrium and systolic in the atrialized chamber) increase the pressure in the right atrium. The increased right atrial pressure, in association with the atrial septal defect, produces cyanosis, arrhythmias, and right heart insufficiency, particularly in types C and D.
CLINICAL PRESENTATION
In neonates symptoms of respiratory failure and cardiac failure with cyanosis are predominant. High pulmonary resistance with impairment of right ventricular function and tricuspid regurgitation generate a “functional pulmonary atresia.” Medical management includes prostaglandin infusion and ventilation until the natural decline of the pulmonary resistance allows anterograde pulmonary blood flow.
Clinical manifestations are directly correlated with anatomical types.
In children and adults dyspnea is the major cause of disability. Discrete cyanosis and cardiac arrhythmias are observed with great frequency. The incidence of arrhythmias ranges between 22% and 42% of patients, 5% to 10% of whom have Wolff-Parkinson-White (WPW) syndrome. Auscultation reveals various anomalies, such as double first sound and systolic murmur at the apex without reinforcement at inspiration. An electrocardiogram typically shows a electrical right axis, an increased P-R space, and a right bundle branch block with polyphasic complex in V 2 to V 4 . Congestive heart failure occurs from poor right ventricular contractility and appears at a later stage as a result of tricuspid insufficiency and/or ventricular obstruction. The obstruction results from interchordal space obliteration, separation of the inflow and outflow chambers by a restrictive orifice, and reduced contractility of the right ventricle.
PREOPERATIVE WORKUP
Both chest x-ray and CTS scan show a typical globular aspect of the cardiac silhouette resulting from severe dilatation of the right atrium and the atrialized chamber ( Fig. 24-5 ). Two-dimensional echocardiography and transesophageal echocardiography allow assessment of the level of attachment of the leaflets, the number and position of papillary muscles, and the motion of the anterior leaflet, all of which aid in the determination of the type of malformation and the expected difficulty of the valvular reconstruction. Echocardiography also helps identify associated congenital anomalies, the most frequently encountered being atrioseptal defect. The evaluation of right ventricular function is difficult by echocardiography. Cardiac magnetic resonance imaging clearly shows the large atrialized chamber with the small right ventricle and reduced size of the left ventricle ( Fig. 24-6, a ). Cardiac catheterization usually discloses a moderately elevated right atrial pressure and a right-to-left shunt at the atrial level. The right ventricular pressure is often within normal limits. Exercise testing and measurement of oxygen consumption (VO 2 max) are helpful to determine surgical indications.
SURGICAL INDICATIONS
Surgical treatment is indicated in the presence of severe cyanosis, congestive heart failure, or severe arrhythmia. Mixed oxygen saturation of 85% or less than 20 ml/kg/min at rest or during exercise is an indication for surgery.
Patients with supraventricular tachycardia and flutter are best treated by endocardial ablation. In cases of unsuccessful ablation, since medical treatment with beta-blockers and amiodarone should be avoided because of side effects in children, an early operation can be indicated for rhythm disturbances.
Indications for asymptomatic patients are not usual except when the cardiothoracic ratio is greater than 65% and the right atrium is markedly enlarged with severe tricuspid regurgitation, conditions that carry a risk of sudden death. The measurement of VO 2 max during exercise provides useful information.
SURGICAL TECHNIQUE
The main features of Carpentier’s technique are the following:
- 1.
Temporary detachment and mobilization of the anterior and posterior leaflets
- 2.
Longitudinal plication of the atrialized chamber and the adjacent right atrium
- 3.
Repositioning of the anterior and posterior leaflets at the tricuspid annulus
- 4.
Remodeling and reinforcement of the tricuspid annulus using a prosthetic ring, except in young children
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