Current Status of Tricuspid Interventions
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Current Status of Tricuspid Valve Treatment
Tricuspid valve (TV) treatment, at its current status, represents a real dilemma since different options are available but long-term results still to be seen and lots of new strategies are still to come.
The current gold standard treatment is represented by TV surgery, particularly in two different cases:
1) Concomitant tricuspid surgery at the time of left-side valve surgery, which goes beyond the present paper’s scope.
2) Isolated tricuspid valve surgery: late tricuspid regurgitation (TR), atrial TR due to annular dilatation, organic or iatrogenic (lead induced) TR, and endocarditis induced TR were distinguished. The first two mentioned represented the most frequent cases (90 percent in Europe and the US) and will be the focus of this analysis.
TR is a progressive disease, and if the treatment is delayed the annulus, which is the more prominent cause of TR, will progressively dilate and severely damage the valve, leading to a more complicated clinical condition; Table 1 shows schematically TR progression stages. The take-home message is that TR should be addressed as early as possible.
Figure 1 puts into relation the five different TR progression stages with the surgical treatment options that are currently available. Interestingly enough, if the annulus is too dilated, it’s recommended to replace the valve with a prosthesis in order to avoid TR recurrence (which is around 20 percent for TV repair at that stage).
Concerning the surgical technique, there has been an important improvement in ring types for TV annuloplasty (incomplete three-dimensional rings, etc.) (1).
Nevertheless, Zack et. al. demonstrated still an elevated range of in-hospital mortality (9 percent) despite the technological improvement (2). The reason for this not well-established result resides in the fact that TV pathology is addressed too late and the patient’s presentation is too critical with respect to those who arrive with less advanced disease (3).
The European Society of Cardiology (ESC) guidelines suggest a more precocious treatment of TV pathology considering the right ventricular function and preventing its severe dilatation (4). The guidelines look not only at TV surgical treatment but also at the emerging field of transcatheter repair.
Transcatheter Tricuspid Valve Repair
The present study will focus on the three principal devices for TV repair with CE approval: TriClip (Abbott), PASCAL (Edwards Lifesciences), and Cardioband (Edwards Lifesciences).
The TriClip System is a transfemoral transcatheter edge-to-edge repair (TEER) system that facilitates the reconstruction of an insufficient tricuspid valve through tissue approximation. The repair creates a tissue bridge reducing the vale area and regurgitation jet.
At the moment, the TriClip is available in four different configurations: G4 NT/NTW and G4 XT/XTW (depending on the clip sizes) allowing an independent grasping of the TV leaflets.
Concerning the results, the Triluminate trial showed the two-year outcome after TV TEER (5).
Even though the Triluminate patients were deeply selected and thus do not reflect completely the real practice results, the trial showed an important TR reduction of >1+ or more in 85.4 percent of cases at thirty days and maintained at two years. This reflects good results in the long term not only in the TR reduction but also in the functional status and in hospitalization rate (5).
The TriClip bRight study showed that 90 percent of patients had TR reduction by at least one grade and 60 percent with a reduced TR to moderate or less, showing good safety of the device itself (6).
Concerning the structural part of TriClip, Figure 2 illustrates the principal components. The device is very similar to the MitraClip (Abbott) device with some modifications, as the steering part has been moved more on the guiding catheter and the adjunctive nobe (S/L) that helps the operator to increase the leaflets grasping capability due to a better coaxial projection.
The most important key points concerning correct TriClip positioning are:
1) The trajectory has to be perpendicular to the TV plane. This can be done by using the S/L and F/E nobe.
2) The clip should be placed perpendicular to the coaptation line of the target lesion. This is particularly important to prevent any kind of leaflet distortion.
The PASCAL (Edwards Lifesciences) is a transfemoral TEER device that acts similarly to TriClip G4 with the independent grasping of the leaflets. This same device can be used for TR and for mitral valve repair.
The first commercial multicenter study focused on PASCAL results for TR, showed a TR reduction < 2+ in 77 percent of patients and TR reduction > 1+ in 92 percent of cases (7). Also, the functional status (NYHA class and 6mwt) showed a significant improvement.
An interesting example of PASCAL implantation is shown in the video associated.
What is really mandatory in TEER procedure (TriClip and PASCAL) is the patient selection. Table 2 shows what patient selection should look like. The imaging section is particularly important and can be a useful guide in TEER visualization and positioning.
Cardioband (Edwards Lifesciences) is a transfemoral annuloplasty device. The rationale of this device is to implant a band from the anteroseptal commissure in a clockwise fashion. It is particularly indicated in central TR with the aim of recreating a normal coaptation.
Concerning the results, Cardioband showed 100 percent procedural success and 77 percent did not have major complications at thirty days (8). Interestingly enough, TR reduction and functional status at follow-up showed a similar result compared to TEER devices (8).
When TV Cannot Be Repaired
There are cases in which the aforementioned devices cannot be used for TV repair. The principal reasons are pacemakers that lead to induced TR and annular dilatation that is too severe.
In these cases, a different approach must be chosen: heterotopic tricuspid valve implantation (Tricento and Tricvalve). In both cases, the TV is left in place.
In Tricvalve the prosthesis is implanted into the superior and inferior vena cava, and in Tricento it is in the right atrium. They represent a symptomatic treatment since they reduce pressure in the venous system and at the liver level.
Concerning preprocedural planning, cardiac computed tomography (CT) is the gold standard.
A novel platform in the case of TV replacement is represented by the Evoque valve (Edwards Lifesciences). It is a transfemoral implantable valve.
The key point of this device is the abolishment of TR with good safety results (9).
The final important concept is to shape the correct TV treatment according to the TR stage, which can be seen in Table 3. As said before, the more critical the stage becomes, the more TV replacement becomes the real option.
The final question is: Does transcatheter tricuspid valve intervention improve survival (10)?
Promising results are seen, but in the end, ongoing randomized trials will give more answers to lots of questions that are still making TV treatment a real dilemma.