Is the diameter of tricuspid annulus or functional tricuspid regurgitation the key parameter for performing ‘prophylactic annuloplasty’?

I read with great interest the paper by El-Khoury’s group from Brussels who showed with their randomized trial that prospective tricuspid annuloplasty, irrespective of annular dilatation at the time of mitral surgery, reduced the recurrence of moderate or severe functional tricuspid regurgitation (TR) at the 5-year follow-up and also reduced the pulmonary pressure. The functional capacity, the right ventricle (RV) ejection fraction, the RV end-systolic volume and the RV end-diastolic volume remained similar [1]. Current guidelines suggest that tricuspid valve annuloplasty may be beneficial in patients with trace or mild functional TR and a tricuspid annulus (TA) diameter ≥40 mm by echocardiography or 70 mm by direct inspection of the tricuspid valve (TV) during surgery for left-sided valve lesions (class 2a) [2]. Is it time to challenge the notion of the diameter of TA and the cut-off value of 40 mm? Should we repair a valve that does not leak but because it is dilated? Which parameter will guide us—the diameter of the annulus of the TV or functional tricuspid regurgitation? Functional regurgitation is a perplexing problem [3]. It is disabling and affects patients’ survival. David et al. [4] showed that TA ≥40 mm did not predict the development of postoperative TR after mitral valve (MV) repair for degenerative diseases. Preoperative TR was the strongest predictor of postoperative TR. As the authors noted, the TV leaflets and MV leaflets varied in size in degenerative diseases. Patients with fibroelastic deficiency had small TV leaflets and a TA of 40 mm was probably too large, so a tricuspid valve annuloplasty might be necessary to prevent late TR. But patients with myxomatous degeneration of MV frequently had large MV leaflets, TV leaflets and larger annuluses, so a TA of 40 mm was rarely associated with severe TR and if so, it was due to leaflet prolapse and not to annular dilatation. Most of their patients had myxomatous degeneration of MV. They also found that the diameter of TA correlated modestly with the size of the mitral annulus (MA) and the severity of preoperative TR, but not with the degree of myxomatous degeneration. The ongoing CTSNet randomized trial (Evaluating the Benefit of Concurrent Tricuspid Valve Repair during Mitral Surgery) might help us to draw more conclusions.