Fig. 23.1
Echocardiographic apical four chamber view demonstrating measurement of the tethering height at mid-systole. This is the distance between the plane of the tricuspid annulus and the coaptation point or theoretical coaptation point of the leaflets at mid systole
The tricuspid regurgitation (TR) is always severe in these cases and intervention on the tricuspid valve at the time of left sided heart valve surgery is usually indicated. However, adequate assessment of right ventricular function is advised prior to surgery to ensure that there is enough right ventricular function and reserve to cope with a competent repaired tricuspid valve. This is discussed in greater detail in a separate chapter.
Severe leaflet tethering, when present, cannot be addressed by tricuspid annuloplasty alone, which only addresses the tricuspid annular dilatation, as the recurrence rate of TR in such cases of 15–30 % is significant [7–13]. In some cases of severe leaflet tethering, the annulus is not dilated, and doing an annuloplasty would not address the problem (Fig. 23.2). Leaflet tethering has been shown to be a predictor of residual TR at the time of hospital discharge following tricuspid annuloplasty, and of recurrent TR following tricuspid annuloplasty [11, 13, 14]. Re-operations in these patients carry a very high hospital mortality and these patients also have a reduced survival [10].
Fig. 23.2
Example of a patient with severe leaflet tethering but without annular dilatation. The tricuspid annular diameter was 38 mm
The leaflet tethering has to be adequately addressed surgically to ensure long term durability of the tricuspid valve repair. The most common technique used to address significant tricuspid leaflet tethering is to augment the tricuspid valve leaflet [15, 16]. Other techniques which have been described include the clover technique, whereby the central part of the free edges of the leaflets are sutured together [17]. Tricuspid valve replacement is an option if significant TR persists despite the use of these repair techniques.
Tricuspid Leaflet Augmentation
Augmentation of the tricuspid valve leaflet was first described by Dreyfus, et al. in 2008 [15]. The principle of the operation is to increase the surface area of coaptation of the leaflets by increasing the size of the anterior leaflet using autologous pericardium. The autologous pericardial patch becomes the new body of the leaflet, and the whole of the native leaflet is the new coaptation surface which is brought towards the other leaflets allowing a generous surface area of coaptation and restoring valve competency (Fig. 23.3). The level of leaflet coaptation may still be occurring below the annulus but a generous surface of coaptation is present ensuring durability of the repair. The anterior leaflet is normally augmented as this is the leaflet most easily enlarged, and it is also usually the most significantly tethered, together with the posterior leaflet, due to their attachments to the anterior papillary muscle and hence to the free wall of the right ventricle [15]. The posterior leaflet can also be augmented if needed in addition to the anterior leaflet [16]. The septal leaflet is often small and redundant and not easily augmented although it is also possible to do so in selected cases with persistent TR after augmentation of the anterior and posterior leaflets. Tricuspid leaflet augmentation has also been used with good results in severe TR secondary to rheumatic valve disease, in these cases, to address the loss of leaflet surface area due to the severely fibrotic and retracted leaflets [18].
Fig. 23.3
Operative technique for anterior leaflet augmentation (From Dreyfus et al. [15]). (a) The anterior leaflet is detached from the annulus from commissure to commissure. (b) An autologous pericardial patch is sutured to the defect created. (c) An annuloplasty ring is implanted. (d) The autologous pericardial patch forms the new body of the leaflet, the native anterior leaflet forms the coaptation surface
Operative Technique
A patch of autologous pericardium is harvested, cleared of fatty tissue and treated in glutaraldehyde for 10 min and then washed in normal saline for a further 10 min. Treatment of the autologous pericardium in glutaraldehyde prevents calcification and retraction of the tissue in later years. The tricuspid valve is detached from its annular attachment along its entire length from the anteroseptal commissure to the anteroposterior commissure (Figs. 23.3 and 23.4). The secondary chordae are inspected and any chords significantly restricting the leaflet are divided. The previously harvested piece of autologous pericardium is cut into an oval shape to fit the size of the defect created. A generous patch is used with the diameter slightly greater than the distance between the anteroseptal and anteroposterior commissures and the height slightly greater than the distance between the annulus and the detached anterior leaflet. Care should be taken during the shaping and suturing of the patch to avoid distorting the normal geometry of the anterior leaflet, particularly its coaptation line. 5/0 Cardionyl suture (Peters Surgical, Bobigny, Cedex, France) or equivalent is used to suture the patch to the annulus on one side and the detached anterior leaflet on the other side. The suture is interlocked after each throw to ensure flat suturing and avoid the purse stringing effect. A tricuspid annuloplasty ring is then implanted sized by measurement of the autologous pericardial patch. A ring which is slightly smaller than the patch is selected (Fig. 23.2).
Fig. 23.4
Operative photographs for anterior leaflet augmentation (From Dreyfus et al. [15]). (a) The anterior leaflet is detached from the annulus from commissure to commissure. (b) The autologous pericardium is sutured to the detached anterior leaflet. (c) The autologous pericardial patch is then sutured to the annulus. (d) An annuloplasty ring is implanted
Augmentation of both anterior and posterior leaflets has also been described. In these cases, the anterior half of the posterior leaflet is also detached in addition to the anterior leaflet and a pericardial patch is used to close the defect [16]. The authors of this technique propose an alternative way to size the pericardial patch based on the size of the annuloplasty ring implanted, typically using a pericardial patch of 13–14 mm in height and 45–46 mm in length for a 28 mm or 30 mm rigid MC3 annuloplasty ring (Edwards Lifesciences, Irvine, CA, USA). In another variation of the technique, the entire anterior and posterior leaflets are detached from the annulus, from the anteroseptal commissure to the anteroposterior commissure. A patch the size of a 32 mm Carpentier Edwards ring is sutured in to fill the gap. At the anteroposterior commissure, the anterior and posterior leaflets are re-attached to the patch next to each other to reconstitute the commissure. The annuloplasty ring is then reimplanted [19].
Results
All the studies have reported good early results with tricuspid leaflet augmentation, with correction of the TR in all cases, reduction of leaflet tethering indices, and right ventricular reverse remodeling [15, 16, 19]. However, longer term follow up is necessary to determine the long term durability of the repair.
Clover (Edge-to-Edge) Technique
The clover technique of tricuspid valve repair was first described in 2004 and was used in patients with complex tricuspid valve lesions including leaflet prolapse from blunt trauma or myxomatous degeneration, and severe leaflet tethering due to ischemic dilated cardiomyopathy [17]. In this technique, the middle of the free edges of the tricuspid leaflets are sutured together using 5/0 polypropylene producing a clover shaped valve. An annuloplasty ring is then implanted to correct annular dilatation and stabilize the repair. At a mean follow-up of 12 months, TR was absent in five patients (38 %), mild in seven patients (53 %), and moderate in one patient (7 %), with no significant gradient across the tricuspid valve both at rest and exercise [17]. It should be noted that only one of the patients in this study had FTR with severely tethered leaflets; the lesion in all the other patients was leaflet prolapse secondary to blunt trauma or myxomatous degeneration. A potential limitation with the use of this technique in severely tethered leaflets is that although valve competency may be restored, this is achieved with increased leaflet tension which may limit the durability of the repair.
Tricuspid Valve Replacement
Replacement of the tricuspid valve is another option in severe FTR with severely tethered leaflets. It may be necessary if repair techniques with leaflet augmentation have failed to correct the TR and in cases of recurrent TR.
Choice of Prosthesis
Studies comparing mechanical and biological tricuspid valves have shown similar operative mortality, freedom from re-operation and survival between the two types of prosthesis [20–24]. Although patients receiving a mechanical tricuspid valve have a higher incidence of valve thrombosis, embolism and bleeding, patients receiving a bioprosthetic tricuspid valve have a higher incidence of structural valve deterioration, so that the valve-related event free survival and overall survival rates were not significantly different between the two groups [23, 24]. However, most studies do not extend beyond 10 years and the increased structural valve deterioration with bioprosthetic valves with time may outweigh the thrombosis, embolism and bleeding risk with mechanical valves over a longer time period particularly in younger patients. One meta-analysis comparing mechanical and biological prosthesis at a median follow-up of 7.3 years showed that the survival and freedom from re-operation was similar for both types of valves [21]. The thrombosis rate of mechanical valves in the tricuspid position was 0.87 % patient per year while the structural valve deterioration in biological valves in the tricuspid position was 1.02 % patient per year mainly due to pannus formation (p = 0.25) [21]. The traditional belief that mechanical tricuspid valve prosthesis have a high incidence of valve thrombosis, and that biological tricuspid valve prosthesis have a very low incidence of structural valve deterioration therefore appears untrue. Interestingly, in this meta-analysis, 97 % of patients with a bioprosthetic tricuspid valve were receiving anticoagulation. Some authors recommend lifelong anticoagulation even for bioprosthetic tricuspid valves due to the possibility that thrombosis may be the mechanism involved in pannus formation [25, 26].
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