By Jeffrey Zimmet, MD, PhD

Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center

SYNOPSIS: In two trials of transcatheter devices treating tricuspid regurgitation, the authors observed high efficacy and low adverse event rates.

SOURCES: Lurz P, Stephan von Bardeleben R, Weber M, et al. Transcatheter edge-to-edge repair for treatment of tricuspid regurgitation. J Am Coll Cardiol 2021;77:229-239.

Kodali S, Hahn RT, Eleid MF, et al. Feasibility study of the transcatheter valve repair system for severe tricuspid regurgitation. J Am Coll Cardiol 2021;77:345-356.

It has been called the forgotten valve. In the past, the importance of marked tricuspid valve regurgitation (TR) has been downplayed or simply pushed aside, at least in part over a lack of good therapeutic options. The high morbidity and mortality rates associated with surgical repair or replacement of the tricuspid valve certainly has dampened the field. In recent years, the MitraClip edge-to-edge repair device has been used in an off-label fashion to treat the tricuspid valve. Multiple devices, all still investigational in the United States, seek to use the basic paradigm of the MitraClip platform for tricuspid repair.

One of these devices is called the TriClip Tricuspid Valve Repair System, conceived and manufactured by the same company that markets MitraClip (Abbott). The TriClip was studied in a prospective, multicenter, single-arm investigation known as TRILUMINATE. These authors sought to determine the safety and effectiveness of this device. Although the trial was modest in size (fewer than 100 enrolled subjects), the TRILUMINATE authors used an echo core laboratory to perform imaging assessments, and they formed a clinical events committee to adjudicate all events. The one-year results were published recently.

The authors enrolled 85 subjects with significant TR and elevated surgical risk, all of whom underwent successful clip implantation. The mean age of participants was 78 years, with a mean EuroSCORE II of 8.7%. In the initial short-term analysis, 86% of patients showed improvement in TR by at least one grade. At 12 months, 63 of the original 85 patients underwent evaluable follow-up imaging to assess TR. Of the 22 patients with missing data, seven had died, nine had withdrawn from the study or missed visits, and six lacked a readable echocardiogram. There were unevaluable baseline data for one patient, leaving 62 patients for the one-year analysis. A total of 54 of 62 patients demonstrated a sustained reduction in TR by at least one grade, while 70% showed moderate-or-less TR at one year. A detailed assessment revealed patients experienced a significant improvement in right ventricular function, as well as reductions in right ventricular diameter and right atrial volume. Significant improvements in functional status also were recorded. Eighty-three percent of subjects at one year were classified as New York Heart Association (NYHA) class I or II, up from 31% at baseline. Performance on the six-minute walk test and the Kansas City Cardiomyopathy Questionnaire (KCCQ) also were significantly better vs. baseline.

Shortly after the publication of these TRILUMINATE data, a separate group published the results of a study of a different transcatheter option for TR, the PASCAL device in the CLASP TR EFS trial. PASCAL, which features a clasp with a spacer that is meant to bridge the coaptation gap, is functionally similar to the TriClip and is delivered via a procedure that also involves large-bore venous access, general anesthesia, and TEE and intracardiac echo guidance.

The authors enrolled 34 patients in this single-arm feasibility trial. Most patients (88%) presented with functional TR. An implant was delivered successfully in 29 of 34 patients, and 85% of patients recorded a reduction of at least one grade in TR at 30 days. The procedure was safe; the major adverse event rate of 5.9% was attributed almost entirely to post-procedure gastrointestinal bleeding. The authors also observed improvements in NYHA class, six-minute walk distance, and KCCQ scores.

COMMENTARY

The tricuspid valve has been forgotten by many until recently. One problem with all repair modalities, including surgery, is patients have been referred for intervention quite late in their disease course, when the right heart has started to dilate and fail, or when the extent of secondary liver dysfunction is markedly advanced. The lack of less-invasive therapeutic options has contributed to this referral delay. Transcatheter options for tricuspid repair have been limited. Lately, there has been interest in several less direct and clumsier options, such as implantation of a transcatheter valve in the inferior vena cava to protect the liver from the effects of torrential TR. Clinically, the growing experience with the MitraClip has led to more off-label use for the tricuspid position. The development of purpose-built devices for the tricuspid valve gives builds more momentum in this area.

In these small trials, success rates were encouragingly high, with real improvements seen in terms of TR severity, right heart remodeling, and clinical assessments. The evidence so far suggests these procedures are safe, despite relatively long times under general anesthesia, with large-bore femoral venous access. Single-leaflet device attachment (where the clip lets go of one leaflet after deployment) occurred in 7% of patients, which is marginally higher than what has been seen with MitraClip.

Not every patient with tricuspid valve disease will be a candidate for these therapies. Imaging guidance for tricuspid interventions can be challenging, with a significant minority of cases showing poor imaging by transesophageal echo. A full one-third of screening failures in the PASCAL trial were excluded over suboptimal imaging. As this field progresses, expect to see growing options for transcatheter therapeutics for the tricuspid valve. Future trials will have to inform which patients will benefit from these therapies, and when in their disease course they are most likely to benefit.