The procedure begins with aortic occlusion and cardioplegic arrest using antegrade cold blood cardioplegia, as shown in Fig. 17.2. In primary median sternotomies, the cross-clamp includes both the aorta and main pulmonary artery, facilitating subsequent analysis of tricuspid valve competence with right ventricular saline injection. In the setting of prior cardiac surgery, a concerted effort is made to expose enough of the pulmonary artery to also incorporate the cross-clamp, but care is taken to avoid injuring the left phrenic nerve. After the right atriotomy is performed, one stay suture is placed in the crista terminalis and retracted laterally, and two stay sutures (not shown) are placed just cephalad to the true tricuspid valve annulus at 10 o’clock and 2 o’clock. The left heart is vented with a catheter inserted across the patent foramen ovale or atrial septal defect until the latter part of the procedure, when it is closed prior to cross-clamp removal. Atrial-level shunts are closed completely in the adult with Ebstein anomaly because the risk of paradoxical embolism has been well documented in such patients. The membranous septum is well visualized by its shiny white appearance with adjacent adipose tissue marked by a prominent vein that typically marks the area of the conduction tissue.
The septal leaflet is displaced apically away from the true tricuspid valve annulus, which is a pathognomonic finding of Ebstein anomaly. In severe cases, the septal displacement extends to the right ventricular outflow tract and close to the pulmonary valve. The anterior leaflet is the best developed and most mobile of the three leaflets. Mobility is usually optimal under the right ventricular outflow tract toward the pulmonary valve; tethering most often begins in its mid-portion (approximately 12 o’clock to 1 o’clock as seen by the surgeon), moving medially toward the inferior leaflet. The inferior leaflet has varying degrees of mobility, depending on the presence or absence of right ventricular atrialization. In general, when there is a well-developed inferior leaflet, there is minimal or no atrialization of the right ventricle. Alternatively, when the inferior leaflet is absent, there is a large segment of atrialization of the inferior wall of the right ventricle. Importantly, these anatomic features differ from patient to patient. Atrialization is marked by the absence of trabeculations internally, and the line between trabeculated and atrialized right ventricle is very clear; it is essentially a straight line. The true tricuspid valve annulus is dilatated; dilatation can be severe in the adult patient. Figure 17.3 shows the beginning of surgical mobilization of leaflet tissue by incising the anterior leaflet away from the annulus at 10 o’clock and extending the detachment in a clockwise manner all the way around the annulus until leaflet tissue ends, typically at about 2 or 3 o’clock, depending on the degree of development of the inferior leaflet. The leaflet is first detached from the annulus and then a surgical mobilization process is performed by working from the annulus toward the apex of the right ventricle. The dotted line marks the end of the anterior leaflet tissue, with only a small portion of inferior leaflet tissue. The dotted line also represents a linear attachment of the leading edge of the anterior and inferior leaflets distally, which should be incised along the dotted line all the way down to the most distal point of the anterior leaflet. The attachments between the body of the anterior and inferior leaflets and the free wall of the right ventricle are usually a combination of both muscular and fibrous attachments. All attachments between the body of the leaflets and the free wall of the ventricle are surgically divided so that the only remaining attachments supporting the leaflet(s) are chordal attachments to the leading edge. In Fig. 17.4, surgical division of these abnormal muscular and fibrous attachments is clearly demonstrated. The surgeon should have a mental image that there should be no attachments between the body of the anterior and inferior leaflets and the free wall of the right ventricle. The only attachments that persist after complete surgical mobilization (i.e., surgical delamination) are the chordal attachments to the leading edge of the anterior and inferior leaflets. This is the most challenging and intimidating portion of the procedure and the reason for the steep learning curve. The common mistake is failure to divide all attachments; the consequence of a single residual attachment is tethering of that leaflet and the inability of the leaflet to move down toward the ventricular inlet to coapt with surrounding leaflet tissue to attain competence of the valve.