Surgical Treatment of Tricuspid Valve Diseases

Tricuspid Valve Annulus

Whereas the base of the anterior and posterior leaflets is attached to the free wall of the right ventricle, the septal leaflet is inserted into the base of the interventricular septum. This line of leaflet attachment, known as the tricuspid valve annulus, is more a landmark than an actual fibrous ring. This absence of an encircling fibrotic structure explains the large changes in the tricuspid valve orifice during the cardiac cycle and its easy dilation in disease. The mobility and size of the tricuspid valve orifice are dependent on the transversely oriented myocardial fibers that surround the atrioventricular valves according to the breaking studies on anatomy and function by Torrent-Guasp and colleagues and Buckberg and colleagues over the past 15 years. Tsakiris and associates found in a canine model that the size of the tricuspid valve orifice changed continuously during the cardiac cycle. The orifice area contracted (from its maximal diastolic size) by 20% to 30%. Tei and associates confirmed these findings in humans with echocardiography. Hiro and colleagues and Jouan and colleagues, working with Duran, analyzed an ovine model for the changes in the normal tricuspid valve orifice during the cardiac cycle as detected by the changes in distance between ultrasound crystals placed around the line of insertion of the leaflets ( Fig. 81-1 ). The tricuspid valve orifice area expands and contracts twice during the cardiac cycle. Orifice contraction begins during the isovolumic relaxation phase of the cardiac cycle and continues through the first half of diastole. Starting with the beginning of isovolumic contraction, a second contraction occurs during ejection, which reduces the tricuspid valve orifice to its minimum area. This contraction corresponds to closure of the valve completed at the end of isovolumic contraction.

The reduction in orifice perimeter is not uniform. The segment of the annulus corresponding to the septal leaflet shortens by 12%, the anterior segment by 15%, and the posterior segment by 17%. The dilation of the annulus occurs in the anterior and posterior segments, and the dilation of the septal segment is restricted because of the relationship with the cardiac fibrous skeleton. This narrowing of the tricuspid valve orifice is due not only to contraction of its perimeter but, more important, to changes in the shape of the annulus. During contraction, the orifice becomes more elliptical because of displacement of the anteroposterior commissure toward the septum and the bulging of the septum. As in the mitral valve, the “annulus” is not in a single plane. In fact, the tricuspid valve annulus is saddle shaped, with its horn or pommel corresponding to the area of the anteroseptal commissure and its cantle to the midpoint of the base of the posterior leaflet ( Fig. 81-2 ). This saddle shape or hyperbolic paraboloid, well known to architects as an ideal design to reduce building tension, has been shown in the mitral valve to significantly reduce peak leaflet stress. Furthermore, the increase in the saddle shape during contraction has a “folding” and reducing effect on the normal tricuspid valve orifice. In cases of tricuspid regurgitation, besides an increase of tricuspid valve annulus area, there is an increase in planarity or flattening of the normal annulus, which induces leaflet tethering. Rigid structures, such as stented prostheses and rigid annuloplasty rings, destroy this configuration and are likely to have a negative impact on the function of the right ventricle.

Leaflets

Although the number of tricuspid valve leaflets varies according to author, it is generally accepted that the tricuspid valve consists of three leaflets. These three leaflets are known as anterior, septal, and posterior, and they are separated by three clefts or commissures named anteroseptal, anteromedial, and posteroseptal ( Fig. 81-3 A ). These clefts do not reach the annulus but delineate small “commissural leaflets.” This is an important surgical point because in cases of fused commissures, their incision should not extend all the way to the annulus; doing so destroys the commissural leaflets. The largest leaflet is the anterior, followed by the posterior, with the septal being the smallest. The excursion of each leaflet (defined as the angle between leaflet free edge and the plane of the annulus) is different. The excursion of the septal leaflet is significantly smaller than that of the other leaflets. This normal, smaller septal excursion might explain the finding at surgery of a septal leaflet plastered against the septum. This finding, often seen in cases of functional regurgitation, is a sign of severity and is a predictor of a poor result after repair.

Chordae Tendineae and Papillary Muscles

The leaflets are held down by marginal and basal chords that arise from three papillary muscle groups. The marginal chords are inserted into the leaflets free margin, and the basal chords are inserted into the ventricular surface of the leaflets. Elongation or rupture of the marginal chords results in leaflet prolapse. The basal chords of the tricuspid valve, although far less prominent than the mitral valve basal chords, probably play a similar role in maintaining valvular and ventricular geometry. In most tricuspid valve cases, three papillary muscle groups are found and can be identified as anterior, posterior, and septal. Whereas the anterior and posterior muscles are virtually always present, the septal muscle might be absent in 20% of patients. The anterior papillary muscle is the longest; it most often has a single head and sustains the largest number of chordae. Elegant anatomic studies by Victor and Nayak in hearts harvested at random confirm that every heart has a unique chordal configuration.

Terminology

New surgical techniques demand deeper knowledge of the anatomy of the region and, consequently, more precise terminology. A common set of anatomic definitions is needed to report precise preoperative and postoperative echocardiographic information important to both the echocardiographer and the surgeon. Aiming to standardize all anatomic findings, Kumar and colleagues developed a detailed tricuspid valve terminology that parallels previously described mitral valve nomenclature. Although it is based on a surgical, atrial view of the valve, their terminology encompasses all three elements of the tricuspid valve apparatus (i.e., leaflets, chords, and papillary muscles).

This alphanumeric system is based on the three papillary muscle groups as defined by the numerals 1 for the anteroseptal, 2 for the posteroseptal, and 3 for the anteroposterior groups of muscles. Each leaflet is identified with the initial letter of its traditional name: S, septal; A, anterior; and P, posterior. Because the lesion does not often affect the whole leaflet or is limited to the chordae, each leaflet is divided into two areas identified by the papillary origin of the corresponding chords. For instance, the septal leaflet (S) is divided into two halves (S1 and S2), identified by the chords that originate from the anteroseptal papillary muscle or the chords that originate from the posteroseptal papillary muscle. The commissures (C) are identified by their papillary origin (1, 2, or 3) as C1, C2, and C3. All chords are identified by their papillary origin and leaflet insertion.

Although it is initially confusing, this nomenclature makes it possible to pinpoint the exact location of a lesion and to describe the surgical maneuvers applied. Its use is particularly significant for reporting of chordal disease and chordal replacement.

Anatomic Relationships

The area corresponding to the anteroseptal commissure is close to the aortic root noncoronary sinus of Valsalva ( Fig. 81-4 ). This fact has important surgical implications because placement of anchoring sutures for a tricuspid valve prosthetic device can be difficult at this level if a stented aortic prosthesis is already present. When a concomitant aortic valve replacement is planned, it is preferable to place the tricuspid valve sutures before undertaking the aortic valve replacement, because tears at this level can be difficult to repair. Of course, the experience and expertise of the operating surgeon finally dictates the operative procedure.

The right coronary artery and sinus run parallel to the segment of the annulus corresponding to the right ventricular free wall. Despite this proximity, injury to these vascular structures in performing a valve replacement or annuloplasty is extremely rare. The ostium of the coronary sinus is situated above the posteroseptal commissure. Because of its distance from the conducting system (close to the right trigone), it is safe to place a pursestring suture around the ostium of the coronary sinus to hold a retrograde cardioplegia cannula. This simple anchoring technique described by Martinez-Leon and colleagues more than 25 years ago allows for a reliable positioning of the retrograde cannula.

Organic Tricuspid Valve Disease

A variety of etiologic factors can induce organic regurgitation, but still today the most frequent cause of organic tricuspid valve disease in urban populations is infective endocarditis ( Box 81-1 ). Tricuspid valve endocarditis used to be relatively rare, with an incidence of only 5% to 10% of patients with infective endocarditis; however, its frequency dramatically increased with the spread of intravenous drug abuse, with a peak incidence until early in the beginning of the twenty-first century. In this population, the tricuspid valve usually has no preexisting pathologic change. The lesions vary from isolated vegetations to total destruction of the valve, including the annulus. Staphylococcus aureus remains the most common organism found in drug addicts, followed by gram-negative organisms and Candida species. Fungal infections are also increasing because of longer periods of invasive monitoring of patients with multiorgan failure in intensive care units.

In the so-called developing world, rheumatic fever is the primary cause of organic valvular heart disease. Typical lesions show varying degrees of leaflet thickening and (most often) commissural fusion. In severe cases, the thickened leaflets become diaphragm-like, with a central circular orifice (see Fig. 81-3 B ). The subvalvular apparatus is seldom affected, and calcifications are rare. Although tricuspid valve stenosis is the classic lesion, predominant insufficiency is just as common. In a series of 253 patients with rheumatic heart disease who underwent tricuspid valve surgery, Prabhakar and colleagues found that organic involvement was present in 45% of the cases and that 45% of them also had annulus dilation. In a classic study of 100 postmortem hearts with rheumatic disease, Gross and Friedberg found microscopic evidence of inflammation in the annulus of all four valves (in the acute rheumatic attack). Rheumatic tricuspid valve disease is always associated with rheumatic mitral valve or mitral-aortic valve lesions. The incidence of chronic rheumatic tricuspid valve disease associated with rheumatic mitral valve disease varies widely, from 6% in an echocardiographic study to 33% in an anatomic series and 11% in the series of Prabhakar and colleagues of 1052 patients undergoing rheumatic valvular surgery. In a Mayo Clinic surgical pathology study of excised tricuspid valves at the time of valve replacement, postinflammatory etiology was responsible for 53% of the 363 valves studied. However, this frequency had diminished from 79% during the period from 1963 to 1967 to 24% during 1983 through 1987, reflecting the reduction in the incidence of rheumatic fever in the United States as it happened across Europe. Out of these regions, rheumatic heart disease is still a major epidemiologic problem. Leaflet tears and total or partial avulsion of a papillary muscle head occur after closed chest trauma. They are occasionally diagnosed at surgery and only classified postoperatively as traumatic by the patient, who recalls an old accident when prompted by the surgeon. As imaging has greatly improved in the past two decades, traumatic tricuspid regurgitation is better diagnosed and characterized.

An occasional cause of traumatic tricuspid regurgitation is that induced by the bioptome during a right myocardial biopsy in transplanted patients. Leaflet tears or chordal avulsion results in severe regurgitation that may require urgent surgery.

Degenerative tricuspid regurgitation associated with mitral valve prolapse is being increasingly observed. This double valve lesion is particularly frequent in Marfan syndrome as a manifestation of a fibrillopathy that also involves the aortic valve and ascending aorta. The reported frequency of tricuspid valve involvement among patients with mitral valve myxomatous disease ranges between 21% and 52% at all ages. Less common causes include organic tricuspid valve lesions secondary to carcinoid syndrome and appetite-suppressant drugs. In both cases, the leaflets are encased by a fibrous sheath that reduces their mobility, resulting in stenotic and regurgitant lesions. Other rare causes are listed in Box 81-1 .

Functional Tricuspid Regurgitation

Functional tricuspid insufficiency is understood to be exclusively due to annulus dilation and dysfunction (see Fig. 81-3 C ). The leaflets, chords, and papillary muscles are otherwise normal. Because of the lack of an anatomic fibrous annulus, the tricuspid valve annulus follows the dilation of the right ventricle. The total perimeter of the normal annulus is approximately 100 to 120 mm. In cases of functional tricuspid regurgitation, the circumference of the annulus can reach 150 to 170 mm. This annulus dilation is nonhomogeneous. In a postmortem study that included normal controls and hearts with rheumatic or myxomatous tricuspid valve disease, Carpentier and colleagues showed that the anterior and posterior segments of the annulus dilated far more than the septal portion of the annulus ( Fig. 81-5 ). This report, 40 years ago, formed the basis for all annuloplasties that selectively reduce the whole annulus except at the level of the septum. The role of the papillary muscles in this setting is debatable, although it can be considered a correctable influencing factor.

In congestive heart failure, functional tricuspid regurgitation is a predictor of poor survival and may be an independent risk factor for the development of cardiac cachexia and protein-losing enteropathy. Cardiac cachexia continues to be a major risk factor in valvular surgery of any origin. Koelling and colleagues studied a total of 1436 patients with left ventricular systolic dysfunction (ejection fraction < 35%). Mitral regurgitation was moderate in 30% and severe in 19% of patients. Moderate tricuspid regurgitation was present in 23% and severe in 12% of patients. Patients with severe mitral regurgitation were more likely also to have tricuspid regurgitation. The association is clear and it is confirmed that the severity of tricuspid regurgitation is related to the degree of congestive heart failure.

Advances in echocardiography have revealed another subvalvular mechanism that applies to both mitral and tricuspid functional regurgitations. Originally observed in functional ischemic mitral regurgitations, this mechanism also applies to the ischemic tricuspid valve and most probably to all functional insufficiencies. Right or left ventricular remodeling induces a lateral displacement of one or more papillary muscles that apically pulls through the basal chords the body of the corresponding leaflet. The leaflet becomes tethered down, losing its coaptation. Tethering in tricuspid valve regurgitation can currently be treated with valve augmentation.

Functional tricuspid regurgitation is an expression of right ventricular failure with a generalized distortion of ventricular geometry. Although annuloplasty can reduce or abolish functional tricuspid regurgitation by reducing the dilated annulus, it does not address the altered subvalvular geometry. Atrioventricular valve regurgitation is therefore influenced by extravalvular factors. Surgery addresses the myocardial component and is aimed at correcting the geometric distortion.

Right ventricular failure and subsequent functional regurgitation are to play a role in the current era of transcatheter valves. If transcatheter valves aim at reducing surgical risks in patients who are deemed inoperable or carrying a risk which is considered too high, the technology and technique should be able to offer better outcomes. In transcatheter repair of mitral regurgitation using the Mitra-Clip (Abbott Vascular, Abbott Park, IL), outcomes are influenced by the residual baseline degree of tricuspid regurgitation. This has been pointed out recently by Ohno and colleagues, confirming that 30-day primary safety endpoint was impaired in the GRASP Registry (Getting Reduction of Mitral Insufficiency by Percutaneous Clip Implantation) patients with moderate or severe residual tricuspid endocarditis. Valve regurgitation negatively influenced death and rehospitalization for congestive heart failure at 12 postoperative months; this is in contradistinction with the results after mitral valve surgery. After mitral valve repair or replacement, the risk of progression of tricuspid regurgitation is low, between 3% and 6% up to 5 years postoperatively. The rationale behind a timely operation on the mitral valve encompasses, too, a reduction in progression of tricuspid regurgitation over time.

Can Tricuspid Valve Disease Be Ignored?

In the early phases of valve surgery, the current knowledge indicated that tricuspid regurgitation in the setting of stenotic valve disease could be solved after mitral valve replacement. This conservative approach was based on the assumption of postoperative regression of pulmonary hypertension, which would reduce the tricuspid regurgitation. However, early reports like that of Duran and colleagues stressed the effect of residual tricuspid regurgitation on outcomes and warned on the need for early repair of mitral lesions and tricuspid organic disease, when analyzing 150 patients with mitral valve repair and concomitant tricuspid valve disease. Almost 40 years later, there is agreement that residual noncorrected tricuspid regurgitation is associated with suboptimal or poor outcomes. These patients with residual uncorrected regurgitation remain at high risk of cardiac death over the follow-up. Reoperative tricuspid patients requiring valve replacement are clinically in poor condition and increased pulmonary hypertension.

Specific Surgical Indications

The severity of the lesion and its reparability are major drivers for the indication for surgery. As stated, the preoperative clinical condition plays a role in the outcomes, too. Severe lesions demand surgical correction regardless of whether repair or replacement will be performed. Moderate lesions should be treated if repair is expected. This principle emphasizes the importance of a precise and accurate preoperative diagnosis. The advances in imaging have allowed better understanding of tricuspid disease and better surgical planning.