The tricuspid valve guards the right ventricular orifice. It consists of a septal leaflet, a large anterior leaflet, and a small posterior leaflet, all three of which are attached to and continuous with the tricuspid ring. These valve leaflets are folds of endocardium strengthened by fibrous tissue. Small accessory leaflets are often present in the angles between the major leaflets. The atrioventricular node lies in the atrial septum adjacent to the septal leaflet, just anterior to the coronary sinus. Its location can be pinpointed at the apex of the triangle of Koch (which is bordered by the septal leaflet, the tendon of Todaro, and the orifice of the coronary sinus). The atrioventricular conduction bundle (bundle of His) extends from the atrioventricular node through the central fibrous body into the ventricles under the membranous part of the interventricular septum. It is approximately 2-mm thick and consists of bundles of fine muscular fibers. There is normally no muscular continuity between the atria and the ventricles except through the conducting tissue of the atrioventricular bundle, but aberrations may exist, which can give rise to rhythm disturbances (Fig. 7.1).

The right ventricular cavity is tubular and triangular in contrast with that of the left ventricle, which is conical. It is bounded by concave anterior and posterior walls and a convex septal wall. There are at least three groups of papillary muscles that stem from the inner aspect of the right ventricular cavity. Chordae tendineae, which are nonelastic chords of tissue, arise from the papillary muscles and fuse to the free edges and the ventricular surfaces of the leaflets of the tricuspid valve. The chords of each papillary muscle control the contiguous margins of two cusps. Hence, chords pass from a large anterior papillary muscle to the anterior and posterior leaflets. A posterior papillary muscle, often represented by two or more components, gives rise to chords that attach to the posterior and septal leaflets. Finally, from a variable group of small septal papillary muscles, chords fan out and fasten to the anterior and septal leaflets of the tricuspid valve. A bridge of muscle, the moderator band, stems from the septum, crosses the cavity of the right ventricle to the free wall, and contributes to the origin of the anterior papillary muscle. A tract of specialized tissue associated with the conduction system runs through the moderator band (Fig. 7.2).

A median sternotomy is the preferred approach for acquired valvular disease because it offers complete exposure for exploration of the mitral, aortic, and tricuspid valves. The tricuspid valve can also be approached through a lower ministernotomy or submammary right thoracotomy (see Chapter 1).

Historically, digital palpation through a purse-string suture on the right atrial appendage was used to assess tricuspid insufficiency before the initiation of cardiopulmonary bypass. Currently, intraoperative transesophageal echocardiography is used to evaluate the tricuspid valve. Because tricuspid insufficiency is load dependent, clinical history, preoperative echocardiography, and/or right heart catheterization data are useful in determining whether the tricuspid valve should be addressed. Some surgeons advocate exploring the tricuspid valve in all patients undergoing mitral valve surgery to directly measure annular size.

When surgery on the tricuspid valve is contemplated, both vena cavae are cannulated directly (Fig. 7.3). A cannula is placed in the ascending aorta, and cardiopulmonary bypass is initiated.

Isolated tricuspid valve surgery can be performed on cardiopulmonary bypass with a warm, beating heart. Most of the time, repair or replacement of the tricuspid valve is performed as part of a combined procedure that includes mitral and/or aortic valve surgery with or without concomitant coronary artery bypass grafting. At the conclusion of these other procedures, the aortic cross-clamp is removed and deairing of the left heart is completed.

The tricuspid valve is then repaired while the patient is being rewarmed.

A longitudinal or oblique atriotomy is made approximately 1 cm posterior to and parallel to the atrioventricular groove. The atriotomy edges are retracted with sutures, and exposure of the tricuspid valve is further facilitated by means of appropriately sized retractors.