If the early 2000s marked the advent of interventional procedures on the aortic valve (e.g., the first TAVI in 2002) and the following decade saw focus on the mitral valve (notably, with Abbott’s acquisition of MitraClip® technology in 2009 and its FDA approval in 2009). The 2020s appear to be witnessing renewed interest in the tricuspid valve. Much has been written about tricuspid regurgitation (TR), though with varying perspectives. From being labeled as a valvular condition with poor prognosis, in line with current trends, to prior publications proposing prophylactic surgery in early, non-severe stages when annular dilation is present; and even earlier, teachings considered TR nearly benign and reversible following correction of left heart disease. This diversity of perspectives has left cardiac surgeons and cardiologists facing a multitude of views, ultimately leading to disorganized approaches in interpreting tricuspid valve disease.

One key misinterpretation lies in equating the right atrioventricular valve’s pathophysiology to that of its left-sided counterpart, the mitral valve. However, the tricuspid valve’s unique features, such as leaflet anchoring independent of papillary muscles (particularly at the septal level), its three-dimensional annulus, anatomical variations of its leaflets, location within a low-pressure and high-capacitance environment, and dependency on pulmonary vascular resistance (partly intrinsic, partly passively transmitted from the left side), make it a singular valve with distinct characteristics. Many of these factors have been previously discussed on this blog.

Despite the clear surgical indications outlined in clinical guidelines, tricuspid valve surgery remains underutilized, particularly in isolated cases. This is likely due to longstanding conceptual confusion and the apparent efficacy of medical management, leading to the current situation. It’s challenging to pinpoint the origin of this vicious cycle, but it likely stems from the traditional under-referral of TR patients for surgery, either due to a misperception of benignity or the reluctance of surgical teams to address cases where the valvular disease is considerably advanced and “ventricularized.” This resistance may have discouraged referrals for surgical intervention. However, the rise of interventional procedures has shifted focus to this patient group, spurring research not only in percutaneous but also in all invasive approaches, including surgical. Enhanced understanding, the development of novel surgical techniques (e.g., subvalvular repair procedures), and improved risk stratification have now opened doors to treating many patients previously relegated to maintenance therapy. Given their ineligibility or lack of knowledge (with the exception of cardiac transplantation) on the use of ARNI, SGLT2 inhibitors, mechanical support, or resynchronization therapy, the outlook for these patients in the therapeutic horizon now attracting attention was bleak.

With this large pool of potential candidates awaiting clinical trials (beyond the Triluminate trial and with no recent surgical trials) to establish the indications for percutaneous therapy, effective risk stratification is essential for determining patient eligibility for either surgical or percutaneous treatment and identifying those for whom the risk would be prohibitive or for whom invasive treatment would likely be futile. In line with the growing interest in tricuspid valve disease, several options have emerged that will likely need refinement over the next few years:

1. TRI-SCORE: This risk scoring system is currently the most suitable for stratifying patients based on conservative versus invasive treatment options, including both surgical and percutaneous procedures. It has also been validated in surgical cohorts, demonstrating good fit and predictive capacity. A previous blog post highlighted that, for TRI-SCORE values of ≤3, surgery yielded superior outcomes to interventional treatment, and this in turn to conservative management, with no group differences for intermediate scores (4-5 points) or high scores (≥6). However, in invasive treatment, benefit over conservative management was observed for intermediate scores when adequate repair with residual TR ≤2+ was achieved. For high scores, there remained no therapeutic benefit of invasive over conservative management, even with successful repair, suggesting a futility threshold for surgical or percutaneous treatment.
2. Conventional Risk Scores: Given that tricuspid valve surgery is ultimately a surgical procedure, traditional risk scoring systems may still play a role, although tricuspid pathology is not adequately represented in EuroSCORE II (only the number of procedures is considered, with most tricuspid surgeries performed in conjunction rather than as isolated procedures) and is not specifically addressed in different versions of the STS score.
3. Disease-Specific Prognostic Factors: The prognosis for tricuspid valve surgery is influenced by factors beyond right ventricular-pulmonary artery coupling (previously discussed in the blog), including organ damage from systemic congestion. Various biomarkers are recognized, though many are not yet incorporated into risk scoring systems or lack established cut-off points for accurate stratification. Nevertheless, these markers should still be evaluated when considering tricuspid valve disease management. These include NT-proBNP, BUN, creatinine, glomerular filtration rate, albumin levels, transaminase levels, bilirubin levels, INR, and platelet count, as well as CA-125, which is overexpressed in congestion. Thus, scoring systems like MELD (Model for End-stage Liver Disease) could play a role in predicting risk in tricuspid valve surgery patients.

Consequently, the authors propose a study including all consecutive patients who underwent isolated tricuspid valve surgery at their institution (Jena, Germany) between 2011 and 2020. Patients with intrinsic tricuspid pathology, functional or primary, were selected, excluding carcinoid, traumatic, congenital, or tumor cases but including those with infectious endocarditis (16%). The MELD score for each patient was analyzed and compared with EuroSCORE II and the STS score (the aortic valve replacement model was used due to the lack of a specific model).

In a sample of 181 symptomatic patients (NYHA class III-IV, TR grade 3+ or higher), more than 75-80% exhibited these criteria. Over 60% had atrial fibrillation, more than 30% had a transvalvular pacemaker/defibrillator electrode, and over 50% had moderate to severe pulmonary hypertension. More than one-third had undergone previous surgery, with 10% having undergone myocardial revascularization, 8% aortic valve surgery, 15% mitral valve surgery, and 13% prior tricuspid procedures. Surgery was performed with a minimally invasive approach via right minithoracotomy in 90% of cases without cardioplegic arrest. The authors emphasized ensuring adequate venous drainage using vacuum assistance and cannulation of both venae cavae. Optimal repair was achieved in 95% (residual TR ≤1+) and acceptable repair (residual TR ≤2+) in 5% of cases. The revision rate for bleeding was notably high (15%), though not discussed by the authors, and other notable complications included stroke (4%) and renal replacement therapy (15%). Several cases required laparotomy due to visceral perforation, abdominal compartment syndrome, mesenteric ischemia, and acute abdomen (not directly related to the surgical procedure).

Thirty-day mortality was 8.9% in the overall series, reaching 65% at maximum follow-up (median 4.4 years). The mean EuroSCORE II was 7.2%, and the mean STS score was 4.9%. The MELD system’s discriminative ability was strong, showing good fit similar to traditional perioperative risk scores. For low MELD scores (<10 points), observed mortality was 4%, with EuroSCORE II and STS scores both predicting 5%. For intermediate MELD scores (10-20 points), observed mortality was 5%, with an average prediction of 8% by EuroSCORE II and 6% by STS. However, predictability varied significantly for high MELD scores (>20 points), where observed mortality reached 31%, well above the 10% and 11% predicted by EuroSCORE II and STS, respectively. This discrepancy may represent a futility threshold for surgical treatment, consistent with previous work discussed on the blog evaluating Child-Pugh (9 points) and MELD (20 points) thresholds as indicative of prohibitive risk in patients with primary hepatic dysfunction undergoing cardiac surgery. The ROC curve yielded a 77% result for STS score and a close 74% for MELD.

The authors conclude that classic risk stratification systems are not highly predictive for isolated tricuspid valve surgery, especially in the presence of secondary liver dysfunction. The MELD score may prove useful in risk stratification for these patients.

COMMENTARY:

This study is of special interest for its originality and pioneering nature, applying existing tools to stratify risk in patients undergoing isolated tricuspid valve surgery. This all-corners study yields ostensibly modest but excellent results, as it includes high-risk patients. Rather than establishing any risk score system as a reference, this study hints at the need for a risk assessment focused on right-sided pathophysiology, similar to the TRI-SCORE initiative. Left-sided pathophysiology principles are not fully applicable, and the positive outcome with a risk scoring system geared towards liver pathology underlines the significance of systemic congestion on surgical risk, an aspect that classic risk scoring systems fail to assess. Future research, possibly aided by big-data and registry analysis, will likely be necessary to develop a new risk scoring system integrating the aforementioned factors. Until then, caution, observation, and common sense are advised… and among the few existing resources, TRI-SCORE (≤3 points) suggests surgical treatment is preferable to intervention.

REFERENCE:

Färber G, Marx J, Scherag A, Saqer I, Diab M, Sponholz C, et al. Risk stratification for isolated tricuspid valve surgery assisted using the Model for End-Stage Liver Disease score. J Thorac Cardiovasc Surg. 2023 Nov;166(5):1433-1441.e1. doi: 10.1016/j.jtcvs.2021.11.102.