Author + information
- aInterventional Cardiology Unit, San Raffaele Scientific Institute, Milan, Italy
- bInterventional Cardiology Unit, EMO-GVM Centro Cuore Columbus, Milan, Italy
- ↵∗Address for correspondence:
Dr. Azeem Latib, Interventional Cardiology Unit, San Raffaele Scientific Institute, Via Olgettina 60, 20132 Milan, Italy.
The tricuspid valve (TV) was virtually ignored in the past, particularly because symptoms from functional tricuspid regurgitation (FTR) may often be vague and heart failure symptoms can be controlled with diuretic therapy. However, significant FTR frequently accompanies left-sided heart valve pathology and usually does not reverse after left-sided surgery (1). Unfortunately, the TV is sometimes “forgotten” at the time of mitral or aortic surgery due to underestimation of the severity or perhaps unjustified concerns about the added surgical risk of tricuspid repair (2). If left untreated, tricuspid regurgitation (TR) can progress and will result in a progressive right ventricular (RV) dilatation and failure, which is associated with a poor prognosis and poor quality of life. Moderate to severe TR is present in at least 1.6 million U.S. individuals, but <8,000 patients currently undergo surgical repair or replacement that may be associated with a relatively high risk of morbidity and mortality, especially in patients undergoing repeated surgery (3). For those patients, new percutaneous transcatheter approaches are becoming available to address this unmet clinical need.
In the wake of a previous report showing the technical feasibility from the compassionate use of the TriAlign system for the treatment of FTR (4), Hahn et al. (5) report 30-day results of the SCOUT (Early Feasibility of the Mitralign Percutaneous Tricuspid Valve Annuloplasty System [PTVAS] Also Known as TriAlign) study in this issue of the Journal (5). SCOUT enrolled 15 symptomatic patients with at least moderate FTR to undergo treatment using the TriAlign system, which replicates the modified Kay procedure. The investigators and patients are to be congratulated for completing the first U.S. Food and Drug Administration-approved early feasibility study in structural heart intervention. This well-conducted study with independent core laboratory analysis will lay the foundation and set the standard for future investigations into the percutaneous treatment of TR. Briefly, the most relevant findings are as follows:
• The TriAlign device was successfully implanted and plicated in all patients. The procedure was safe and without deaths, strokes, access-site complications, or valve reintervention at 30 days. One procedure was complicated by right coronary artery (RCA) narrowing secondary to extrinsic compression from a pledget too close to the artery. At 30 days, 3 pledgets detached from the annulus without any need for reintervention.
• In the as-treated population (without pledget detachment), the echocardiographic results are encouraging, with a significant reduction in multiple measurements of TR severity such as mean vena contracta diameter, tricuspid annular area, and effective regurgitant orifice area by proximal isovelocity surface area. Although the reduction in TR seems modest at first glance, this is probably related to the baseline TR, which was torrential and associated with severe annular dilation and a distance between the posterior commissures that is >2.8 cm of plication achieved with a single pair of pledgets. Although TR grade is not reported, the current scale of TR grade may not be sufficiently wide to capture the complexity of this patient group, and thus, when evaluating efficacy, we should look at percentage reduction from baseline rather than absolute values.
• Efficacy in the reduction of TR was associated with significant improvements in symptoms and quality of life.
There are a number of devices with varying mechanisms of action that are under pre-clinical and clinical evaluation for transcatheter tricuspid repair (Figure 1). TriAlign may offer specific advantages such as the small footprint; preservation of underlying anatomy; ability to customize the location of the implant; is based on a surgical repair technique predicate; and the possibility of repeating the procedure in the future. However, insufficient plication distance from a single pair of pledgets in larger annuli, procedural length, requirement for a posterior shelf of annular tissue, and risk of dehiscence if plication distance or annular tissue quality is inadequate are possible limitations. There are a number of lessons that can be gleaned regarding these novel approaches to FTR, as follows:
• The TV and annulus pose a number of anatomical challenges such as proximity of the RCA, annular and leaflet tissue appear to be more fragile than that of the mitral, and catheter navigation in the right atrium is not well delineated.
• All annular-based devices will require sufficient annular tissue for anchoring, have a small risk of RCA injury, be prone to dehiscence if tissue quality is poor or excessive force is applied to the tissue, and possibly have limited effectiveness in patients with advanced RV disease and excessive tethering.
• Current widespread knowledge of the performance of standardized imaging required for the interventional guidance of transcatheter tricuspid procedures is lacking. However, Hahn et al. (5) have led the way in shining the spotlight on the forgotten valve.
• All the studies have variable endpoints and different measures for evaluating efficacy such as annular reduction, TR grade, vena contracta, or effective regurgitant orifice area. This begs the question as to what the correct echocardiographic and clinical endpoints should be for a transcatheter repair study, other than reduction in TR. Probably, quality of life, rehospitalization for heart failure, and diuretic dose are more appropriate endpoints.
• Unknown efficacy exists in patients with transtricuspid pacing or defibrillator leads, which are present in 40% to 50% with severe TR.
• Clinical data are insufficient for many of the devices, limiting any conclusions regarding safety or efficacy.
• Similar to the problem with mitral repair devices, durability of the repair must be proven with longer-term clinical data.
• Finally, the most interesting observation from treating this cohort of patients with severe FTR appears to be that the relationship between TR reduction and symptom improvement is not linear (i.e., a number of devices have shown a marked improvement in symptoms that is disproportionate to the degree of TR reduction). This again highlights the importance of choosing the correct endpoints.
The most challenging aspect of entering into this new era of transcatheter tricuspid intervention is not only the steep learning curve required but the fact that most patients who are currently being referred for treatment have massive TR, severe pulmonary hypertension, and right-sided heart failure refractory to diuretic therapy. These patients are often considered inoperable and are unlikely to benefit from a percutaneous tricuspid intervention that conversely may even worsen RV function. In order to truly tackle the challenges of developing safe and effective percutaneous approaches to FTR, we will need to leverage what we have learned from transcatheter mitral interventions and tricuspid valve surgery:
• Selection of patients who are most likely to benefit and correct timing of the intervention;
• Detailed pre-procedural planning with MSCT to evaluate anatomical suitability such as identifying the target site, assessment of tissue quality by Hounsfield units, location of RCA, and aid fluoroscopic guidance;
• Device iterations to overcome current limitations, especially regarding avoidance of dehiscence or detachment;
• Reproducing surgical techniques more accurately. The distance between the posterior commissures is often >4 cm, and thus, the SCOUT-II CE mark study will allow implantation of 2 pairs of pledgets, which will increase efficacy in larger annuli and lower the risk of pledget dehiscence because plication distance for each pair will be 2.0 to 2.5 cm.
• Developing an anatomic or patient-specific device selection based on the presence of pacing leads, degree of annular dilatation, RV function, or leaflet tethering. In order to fully address the anatomical complexities, we will need a toolbox of devices with some patients requiring multiple repair devices or even replacement.
• Standardized definitions and endpoints for transcatheter tricuspid intervention are needed so that the different devices can be objectively evaluated.
If the field of transcatheter TV intervention is to be successful, we need to rethink how we currently approach FTR. Diuretic therapy improves symptoms and reduces volume overload but do not change the course of the disease once annular dilatation occurs. Thus, in order for these therapies to be truly effective in changing the natural history of FTR, the cardiology community needs to challenge the conventional approach to the TV. We need to stop ignoring the TV or making excuses for not treating moderate to severe FTR with annular dilatation. Surgical repair of annular dilatation at the time of left-sided heart surgery should become standard practice, and earlier treatment of significant TR, regardless of whether surgically or percutaneously, needs to become widely accepted.
↵∗ Editorials published in the Journal of the American College of Cardiology reflect the views of the authors and do not necessarily represent the views of JACC or the American College of Cardiology.
Dr. Latib is a consultant for 4-Tech, Mitralign, Millipede, and Valtech Cardio; and has received speaker honoraria from Abbott Vascular. Dr. Mangieri has reported he has no relationships relevant to the contents of this paper to disclose.
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