Fig. 17.1
Surgical incisions to access the right atrium and expose the tricuspid valve
In the first case, the incision is carried out starting close to the atrial appendage and directing it to the inferior vena cava. When a trans-atrial approach is planned to perform mitral valve surgery, the right atriotomy must be more extended to allow its exposure [1]. In this cases the incision is parallel and posterior to the atrioventricular groove, one centimeter far away from it, to avoid injury to the right coronary artery or to the sinus node.
The second approach consists in performing a vertical right atriotomy starting from the appendage and directing the incision straight towards the interatrial groove.
Some surgeons adopt a semicircular atriotomy proximally to the inferior vena cava. This kind of approach seems to provide direct visualization of the tricuspid valve and reduce the risk of damaging the conduction system (Fig. 17.1).
The accuracy of all those incisions is mandatory to perform a safe and seal closure of the atrium at the end of the procedure.
Once the atriotomy is completed, exposure can be obtained with the help of a standard retractor or using silk stay sutures passed through the pectinate muscles.
Surgical Anatomy and Analysis
The tricuspid valve is composed of three leaflets, anterior, posterior and septal, and three interposed commissures.
The leaflets are implanted on the tricuspid annulus, a relatively indistinct fibrous structure localized about 2 mm external and deep from the hinge of each cusp. This structure has several significant relationships so understanding its exact position is fundamental to safely perform any annuloplasty technique.
In the first instance, it is crucial to identify the triangle of Koch that is defined by the tendon of Todaro , the septal leaflet of the tricuspid valve and the orifice of the coronary sinus. The atrioventricular node and the conduction system are localized at the apex of the triangle (Fig. 17.2). Staying away from this area is essential to avoid rhythm disturbances.
Fig. 17.2
Localization of the atrioventricular node and the conduction system and their relationship with the tricuspid valve annulus
Secondly, during annuloplasty the strict relationship of the antero-septal commissure and the first part of the anterior leaflet with the aortic root must be considered. In this segment, inadvertent stitches may damage the aortic valve.
Finally, right coronary artery (RCA) runs very close to the tricuspid annulus in the area between the anteroposterior commissure and the posterior leaflet especially in the presence of anatomic variations of RCA distribution or whenever relationship between the RCA and the tricuspid annulus is altered due to right ventricle remodeling or severe tricuspid annulus dilatation. Both during suture annuloplasty and ring annuloplasty, careless stitches may distort or occlude the RCA in the segment from the acute margin to the crux. During the operation, once the right atrium is opened, a carefully inspection must be performed to peculiarly visualize jet lesions on the atrial wall. They indicate which is the prolapsing leaflet, which is usually the one opposite to the lesion.
The tricuspid valve is inspected to detect leaflet lesions. Every cusp is analyzed using a nerve hook to expose the subvalvular apparatus.
Tricuspid Valve Repair for Functional Disease
Functional (or secondary) tricuspid regurgitation refers to a disease occurring as result of left-sided heart pathology (LHP) or pulmonary hypertension in the absence of organic lesions of the tricuspid valve.
However, this definition may be somewhat misleading since functional tricuspid regurgitation is more than a functional entity, as it entails intrinsic anatomical abnormalities of the tricuspid apparatus, such as annular dilation and deformation.
The surgical treatment of secondary tricuspid regurgitation is still under debate both in terms of timing and surgical techniques.
Severe secondary tricuspid regurgitation should be corrected at the same time as left-heart surgery is performed. Less than severe functional tricuspid regurgitation should be surgically corrected in cases of concomitant LHP requiring surgery in the presence of tricuspid annular dilation (≥40 mm or >21 mm/m2 between the septal and the anterior leaflet in diastole [2]). Indeed, in those circumstances, the diameter of the tricuspid annulus rather than the grade of regurgitation (which is highly subjective and variable) should be the criterion to indicate the need for concomitant tricuspid valve repair. The principles of therapy for secondary tricuspid regurgitation include elimination of increased after-load to the right ventricle (by correction of LHP and optimization of left ventricular function) and correction of tricuspid annulus dilation and dysfunction, usually by tricuspid valve annuloplasty.
If severe tricuspid valve tethering is present, the use of adjunctive surgical techniques to tricuspid annuloplasty (such as enlargement of the anterior leaflet) or tricuspid valve replacement should be considered. Tricuspid annular dilatation has always been the primary target of the surgical treatment of secondary tricuspid regurgitation and has usually been corrected by two main surgical methods: suture annuloplasty and ring annuloplasty [3].
Suture Annuloplasty
Kay Procedure
The repair described by Kay et al. in 1965 represents the oldest one to treat secondary tricuspid regurgitation. The main principle of this technique is to exclude the posterior leaflet to obtain a competent bicuspid valve. In the original description a 1-0 silk suture is passed in the annulus beginning at the anteroposterior commissure, then at the center of the posterior leaflet, and then through the annulus at the postero-septal commissure. The suture is pulled taut and the size of the orifice is checked. At this point additional sutures are placed and then tighted when the desired size is reached. Usually three or four sutures are required to decrease the size of the annulus [4] (Fig. 17.3a).
Fig. 17.3
(a) Original Kay procedure . (b) Original De Vega procedure
Several modifications to the first bicuspidalization technique have been proposed over the years such as the use of figure-of-eight sutures, pledget mattress sutures, 2-0 or 3-0 polyester sutures instead of silk suture, and few others.
De Vega Procedure
The De Vega annuloplasty is definitely the most popular and widely used suture technique to correct annular dilatation.
Described in 1972, the aim of this technique is to shorten the area of the tricuspid annulus corresponding to the anterior and posterior leaflets.
Two pledgeted parallel running stitches, usually 2-0 Ti-cron or 4-0 polypropylene, are used for this procedure. The suture is started on the annulus at the level of postero-septal commissure and directed around the perimeter of the orifice in a counterclockwise direction reaching the antero-septal commisure. Every 5–6 mm a single bite is placed into the fibrous annulus through the endocardium.
The second extremity of the suture is placed 1–2 mm outside the previous one making the same route. Once reached the antero-septal commissure the suture is tied, possibly using an annular sizer into the valve to properly obtain the desired size (Fig. 17.3b) [5].
Pitfall of this technique is the possibility that stitches placed in a fragile tricuspid annulus cut the endocardium. For this reason a number of modifications have been proposed. One of the most interesting was developed by Antunes and Girdwood in 1983 that suggested to use a pledget between every bite on the annular tissue [6].
Ring Annuloplasty
In 1971, Carpentier proposed a new revolutionary concept in the conservative valve surgery introducing the idea of annular remodeling using a prosthetic ring [7].
With rigid or semi-rigid prosthetic tricuspid ring annuloplasty , the annulus is permanently fixed in a systolic position and the physiologic shape of the valve is restored [8]. Flexible rings may be used as well. Although they do decrease the size of the annulus, they are unable to restore its normal morphology.
Imaging studies of the tricuspid annulus, by means of echocardiographic and magnetic resonance, showed its three-dimensional geometry. The area close to the aortic valve and the right ventricular outflow tract, at the level of the antero-septal commissure, is the most prominent part of the annulus whereas the deepest part is a the level of the postero-septal commissure adjacent to the coronary sinus ostium [9]. Giving this finding, specific rigid rings with a three-dimensional (3-D) shape have been proposed to re-establish as much as possible the annulus geometry.
Classically, measurement of the distance from the antero-septal to postero-septal commissures, or surface of the anterior leaflet, are used for ring sizing.
Once the right size of the ring is chosen, it is implanted using eight to ten 2-0 Ti-cron stitches. The tricuspid annulus is not as distinct as the mitral annulus, therefore each leaflet must be grasped and pulled away from its attachment for a properly exposure.
Usually, suturing starts posteriorly to the midpoint of the septal leaflet, very close to its hinge to prevent injury to the conduction system. Proceeding counterclockwise, the second stitch is placed like the first one, very close to the leaflet and towards the postero-septal commisure. The sutures corresponding to the posterior leaflet, and to the portion of the anterior leaflet away from the aortic segment, have to be placed 2 mm far from the junction between the atrium and the valve. Giving the closeness of the aortic root, the other stitches for the anterior leaflet must be passed through its hinge paying particular attention not to accidentally place a suture into the leaflet itself or to damage the aortic wall. The last stitch must be placed superiorly to the antero-septal commisure, to stay away from the conduction system.
At this point the sutures are passed through the ring using the same spacing for those originating from the septal portion of the annulus, then reducing the space for all the others. The ring is parachuted and fixed, reducing the dimension of the annulus, restoring its geometry and obtaining adequate surface of leaflets coaptation (Fig. 17.4).
Fig. 17.4
Tricuspid ring annuloplasty
Enlargement of the Anterior Leaflet
When severe tethering of one or more leaflets is present, an isolated annuloplasty is not enough to correct the insufficiency and adjunctive procedures are necessary.
In 2008 Dreyfus et al. have proposed the technique described as enlargement of the anterior leaflet to deal with this situation. The anterior leaflet is detached from the annulus and an oval shaped piece of autologous pericardium is prepared. The diameter of the patch is measured on the distance between the antero-septal and the anteroposterior commisures, whereas the height on the greatest distance between the detached leaflet and the annulus. The patch is then sutured with a polypropylene 5-0 suture to the annulus and to the leaflet to fill the gap. The procedure is concluded implanting a semi-rigid tricuspid annuloplasty ring [10].
“Clover Technique”
Another adjunctive procedure which can be associated to the annuloplasty in case of severe functional tricuspid regurgitation due to important tethering, is represented by the so-called “clover technique ”.
This procedure was conceived and then proposed by Alfieri et al. in 2003 [11]: initially introduced for the treatment of post-traumatic tricuspid regurgitation, afterward it has proven to be effective even in complex cases both of primary or secondary tricuspid regurgitation [12] (Fig. 17.5).
Fig. 17.5
The “Clover Technique ”
The technique consists of stitching together the middle point of the free edges of the tricuspid leaflets, producing a clover-shaped valve. In all cases a 5.0 polipropylene suture without pledgets is used. Then a semi-rigid tricuspid ring is implanted to correct the dilated and deformed annulus and to stabilize the repair.
Results
Neither suture nor ring annuloplasty consistently eliminate functional tricuspid regurgitation. After tricuspid annuloplasty, the recurrence rate of significant tricuspid insufficiency at 1 month after surgery ranges from 8 to 15% [13, 14].
This rate of failure has been attributed to a number of factors, including severity of preoperative tricuspid regurgitation, pulmonary hypertension, presence of pacemakers, left ventricular dysfunction, increased left ventricular remodeling, severe tethering of the tricuspid leaflets and the use of suture rather than ring annuloplasty [13–16].
The type of annulopasty procedure remains one of the most investigated aspect in functional tricuspid regurgitation repair. In several published studies, both randomized and observational, the ring annuloplasty has showed a more durable repair compared to suture annulopasty, particularly in patients with severe tricuspid annular dilation or pulmonary hypertension [13–16].
Besides being more durable, ring repairs also provide better long-term and event-free survival up to 15 years after surgery, compared to suture annuloplasty [17]. This is not surprising considering that moderate and severe tricuspid regurgitation is an important predictor of late mortality, independent of ventricular function and pulmonary artery pressure [18].
When a significant leaflet tethering is associated to the dilatation of the tricuspid annulus, annuloplasty alone is unlikely to be durable [19] so an additional procedure, such as patch augmentation of the anterior leaflet or “clover technique ”, may be used to achieve a more durable repair [10, 12]. Although preliminary results with these approaches are encouraging, more data and longer follow-up are necessary to prove their effectiveness in the long-term and define their role as an alternative to tricuspid valve replacement in selected patients.
Tricuspid Valve Repair for Primary Disease
Primary tricuspid valve insufficiency represents an organic disease with involvement of the tricuspid valve apparatus that results affected by one or more lesions.
In Western countries, the most common etiologies of primary tricuspid regurgitation are degenerative valve disease or bacterial endocarditis, whereas rheumatic disease is the most prevalent form in developing countries.
The leaflets may be affected by excess of tissue, thickening, perforation and tear. The chordae tendinae and the papillary muscles may be elongated or damaged. On the other hand chordal or commisures thickening and fusion are typical of rheumatic disease.
The aim of tricuspid valve repair is to restore a normal leaflet mobility ensuring an adequate surface of coaptation. Several techniques, already well-adopted in the context of mitral valve repair, are used to repair these organic defects, and usually a prosthetic ring implantation completes the procedure.
Intervention on the Leaflets
In case of limited chordal rupture or elongation, a small triangular resection of the leaflet can be performed. This technique may be applied when the prolapsing segment is less than one tenth of the leaflet surface area.
Once resected the planned portion, the margins are approximated using a 5-0 polypropylene running suture or interrupted stitches depending on surgeon preferences.
If the prolapsing segment is extensive, usually due to bacterial endocarditis, the resection must be extensive itself and sometimes an annular plication and/or a patching of the resected area must be adopted (Fig. 17.6).
Fig. 17.6
(a) Triangular resection to correct the flail of the leaflet due to chordal rupture. (b) Extensive resection of the leaflet due to bacterial endocarditis. (c) The gap is closed using an autologous pericardium patch
Intervention on the Chordae
When the prolapse of the leaflet is caused by an extensive chordal rupture, a small resection is not adequate and a procedure correcting the subvalvular apparatus should be performed.
Like in mitral valve repair surgery, this kind of defect may be fixed adopting both chordal transposition and artificial chordae implantation.
In the first case, a small segment of adjacent non prolapsing leaflet is resected and then implanted on the prolapsing one using 5-0 polypropylene running suture.
If artificial chordae are preferred, accurate measurement of native chordae of a non prolapsing leaflet is performed and used to choice the proper length. After that, artificial chordae are first implanted on the corresponding papillary muscle, then on the free margin of the prolapsing leaflet.
Intervention on the Papillary Muscles
Papillary muscles or extensive chordal elongation may be corrected adopting a sliding papillary muscle plasty technique. The elongated papillary muscle , or the papillary muscle underlying the elongated chordae, is lowered to the proper level and fixed to the adjacent one using 5-0 polypropylene interrupted stitches.
Intervention on the Commissures
Fusion of the three commissures is the specific feature of the rheumatic disease. In these cases fusion of the underlying chordae is often associated.
The surgical technique consists of performing commissurotomy and dividing fused chordae using an 11 blade under direct visualization; in some cases, with the purpose to improve leaflets motion, cutting of secondary chordae is associated.
Tricuspid Valve Replacement
When the tricuspid valve is dramatically compromised to the point that an adequate reconstructive procedure can not be performed, the decision for tricuspid valve replacement should be taken.
This condition frequently occurs for advanced rheumatic disease, for heavily damaged valves due to endocarditis, for carcinoid syndrome, radiation induced disorder and severe forms of Ebstein’s anomaly .
In functional tricuspid regurgitation valve repair is the first choice. Sometimes, severe tethering does not permit a good immediate results so a tricuspid valve replacement should be considered.
Tricuspid valve replacement (TVR) can be done both under cardioplegic heart arrest or on beating heart. The choice of the strategy is influenced by the surgeon’s preference, accessibility of the tricuspid valve, and overall length of aortic cross-clamping. A combined procedure can also be done, i.e. placement of the principal and most difficult stitches during cross clamp and then finishing the valve implantation on beating heart after aortic declamping.
Choice of the Prosthetic Valve
The choice of implanting a biological or a mechanical prosthesis in tricuspid position should follow the same algorithm used for other cardiac valves. Patients age, contraindication to anticoagulation therapy, female sex, social and working issue must be considered with the purpose to make the right choice.
Some surgeons prefer to implant a mechanical prosthesis in order to avoid the problem of bio-prosthesis structural valve deterioration [20]. However mechanical valves in low-pressure right-heart circulation are more predisposed to valve thrombosis. Moreover, lower level of prostacyclin, a powerful inhibitor of platelet aggregation produced in the lung, is present in the right-sided chamber and it could represent an adjunctive risk factor for mechanical valve thrombosis [21].
Furthermore, introduction of pacemaker leads through the prosthesis into the right ventricle is not possible with mechanical valves.
Given that, biological prostheses would seem to be an ideal solution for tricuspid valve replacement since they do not require anticoagulation therapy and are expected to have a slower degeneration than in mitral position.
Reoperations rate after bio-prosthetic tricuspid valve replacement seems to be lower compared to bio-prosthetic mitral valve replacements. This might be explained by the fact that right heart chambers produce lower pressure and thus generate lower stress on the bio-prostheses. Moreover, patients undergoing TVR usually have a limited life expectancy so the long-term durability of a bio-prosthesis in this position is enough for their natural history [22].
On the other hand, some series have been consistent in demonstrating that there is no survival benefit of biological over mechanical prostheses and also the reoperation rate is similar [23, 24]. In addition a recent meta-analysis showed no statistically significant difference between mechanical and biological valves in terms of survival, reoperation, or prosthetic valve failure, even if mechanical tricuspid valve prostheses had a higher risk of thrombosis [25]. Regarding that, bileaflet valve thrombosis is rarely fatal and often is successfully treated increasing anticoagulation therapy or using thrombolysis [26].
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