The right ventricle and tricuspid valve are no longer viewed as neglected cardiac structures. In recent years, an influx of literature, largely driven by interventional cardiology colleagues, has aimed to elucidate the complex function of this structure. Anatomically, the tricuspid valve comprises three leaflets—anterior, posterior, and septal—attached by chordae tendineae to two papillary muscles. The anterior leaflet is the largest, the posterior leaflet can exhibit multiple scallops, and the septal leaflet is typically the smallest. Accessory chordae often anchor to the free wall of the right ventricle and the moderator band, especially around the septal leaflet and adjacent septo-anterior and septo-posterior commissures. Unlike the horseshoe shape of the mitral annulus, the tricuspid annulus has a three-dimensional structure, with the septo-anterior and antero-posterior commissures at the highest points and the septo-posterior commissure at the lowest point. Thanks to the study by Dreyfus et al. in 2005, we learned that annular dilation occurs along the antero-posterior commissure with right ventricular remodeling. Additionally, with the new tricuspid regurgitation (TR) classification, we know TR can be primary or organic, related to intracavitary pacing devices, and secondary or functional. Functional TR is subcategorized based on the primary chamber causing regurgitation: either due to atrial dilation from atrial fibrillation, stretching the annulus, or right ventricular dysfunction impairing leaflet coaptation through tethering forces. The etiology of TR is crucial as it impacts the prognosis of tricuspid valve interventions. 

According to 2020 American and 2021 European guidelines, it is valid to repair a dilated tricuspid valve with an annular diameter >4 cm (septal-anterior distance) or in patients with symptoms of right heart failure, with a Class IIa indication. Uncertainty arises when regurgitation is less severe and right heart failure symptoms are absent. The Mayo Clinic study aims to evaluate long-term outcomes for 1,588 patients with mitral valve disease and mild or moderate TR, comparing outcomes between those who received a surgical intervention and those who did not. 

Data collection included all patients from 2001 to 2018 who underwent mitral valve surgery with or without concomitant tricuspid valve surgery, assessing pre- and postoperative echocardiograms for TR severity and annular size. Patients with endocarditis, rheumatic or ischemic mitral disease, primary cardiomyopathy, congenital malformations, under 18 years of age, procedures involving MitraClip, reoperations on the mitral and/or tricuspid valve, and concomitant aortic valve procedures were excluded. 

Concomitant tricuspid valve surgery was performed in 235 patients (14.8%). During the study period, the rate of tricuspid valve repair in this context rose from 7% to 20% in the final year. The intervention improved the TR grade independently of the preoperative severity, with these postoperative improvements sustained over time. The annular size did not affect the risk of progression to severe TR (p = .226). The atrioventricular block rate was three times higher (3%) compared to isolated mitral surgery. After adjusting for baseline characteristics and with a median follow-up of 6.5 years, survival was similar between groups. There were 22 late tricuspid valve reoperations (5-year cumulative risk of 1.5%), with severe TR as the primary indication in only 6 patients. Preoperative TR grade and concomitant tricuspid surgery were not associated with reoperation incidence. 

The authors concluded that concomitant tricuspid valve surgery reduces postoperative regurgitation without influencing survival or reoperation incidence. In patients with less-than-severe TR, tricuspid annular diameter was not associated with progression to severe regurgitation. 

COMMENTARY: 

Since the CTSN trial (Cardiothoracic Surgical Trials Network), specifically the CTCR-MVS study (Concomitant Tricuspid Valve Repair + Mitral Valve Surgery vs. Mitral Valve Surgery Alone), tricuspid valve repair in degenerative mitral surgery has been performed more liberally. The CTCR-MVS study recruited 401 patients with mitral valve replacement (repairs were not included) and mild/moderate TR, comparing concomitant surgery to isolated mitral surgery. Results showed less TR progression to severe in the concomitant surgery group (0.6% vs. 5.6%; p < .05), with a trade-off of higher postoperative atrioventricular block rates (14.1% vs. 2.5%; p < .05) and increased cerebral ischemic events (4.5% vs. 1.5%; p < .05), without improved rehospitalization rates or quality of life. Notably, follow-up was only 2 years, and one-third of the patients had moderate TR, with the rest included due to annular dilation. Five-year results from this study, expected this year, will assess mid-term survival differences. 

Each etiology of mitral valve disease with TR has a unique natural history. This was elegantly illustrated in a 2011 Mayo Clinic publication by Yilmaz et al., showing that TR associated with organic mitral disease typically improves following mitral valve treatment. However, in rheumatic mitral disease, TR often worsens, with up to 60% progressing to grade III/IV within 5 years. Patients with ischemic cardiomyopathy experience the fastest TR progression, likely due to biventricular dysfunction. 

Right heart echocardiographic evaluation is more complex than left-sided assessments. For example, magnetic resonance imaging has a shorter learning curve for right-sided evaluation compared to echocardiography. Preload and afterload dependency of the tricuspid valve and right ventricle often lead to discrepancies, such as moderate TR in consultations not appearing on intraoperative transesophageal echocardiography. Dreyfus’ 2005 study systematically measured the septo-anterior to antero-posterior commissure length intraoperatively, establishing a cut-off of 7 cm, distinct from the 4 cm echocardiographic measurement. Variability in preoperative study types and timing complicates results comparison in the literature. 

Today’s study, as a single-center retrospective study, inherently has limitations. Follow-up was not standardized, depending on symptoms or cardiologist discretion, and lacks data on right ventricular function, size, and exercise capacity. Consequently, we do not know if functional improvement justifies concomitant TR procedures despite no survival benefit. 

In conclusion, each additional step in surgery increases morbidity and mortality, warranting careful risk-benefit assessment. For mild/moderate TR with degenerative mitral disease, treating the mitral valve alone generally suffices. Surgical risk, complexity, mitral disease etiology, and progression factors like right ventricular dilation, potential pulmonary hypertension reversibility from left-side repair, or atrial fibrillation presence should inform decisions. As Hippocrates advised, “primum non nocere.” 

REFERENCE:

Hasan IS, Qrareya M, Crestanello JA, Daly RC, Dearani JA, et al. Impact of tricuspid valve regurgitation on intermediate outcomes of degenerative mitral valve surgery. J Thorac Cardiovasc Surg. 2024 Jun;167(6):2091-2101. doi: 10.1016/j.jtcvs.2022.09.035.