Surgical intervention for secondary or functional mitral regurgitation has generated both interest and challenges over the decades. This stems from its complexity as a therapeutic endeavor, aiming to restore coaptation to an anatomically normal valve affected by underlying ventricular myocardial pathology. Numerous approaches have been proposed to address this condition, systematically categorized as annular correction, leaflet correction, and subvalvular apparatus modification.

The surgical approach, primarily restrictive annuloplasty techniques, was initially suggested by Bolling’s studies, utilizing various suture methods or devices like the Carpentier-Adams-McCarthy asymmetrical ring and the now-discontinued Edwards® GeoForm®. However, these strategies proved insufficient in counteracting the subvalvular traction forces that limit coaptation (tenting). Consequently, additional approaches were proposed, such as papillary muscle approximation or anchoring to the posterior or, more recently, the anterior ring (mitral-aortic continuity) as advocated by Schäfers. In cases where annular interventions alone were ineffective, leaflet extension techniques using patches were implemented to maintain the structural integrity of the chordal-papillary apparatus and mitigate further distortion of already compromised ventricular geometry.

When all other repair strategies failed, prosthetic replacement was considered as a last resort, with an emphasis on preserving as much of the subvalvular apparatus as possible, ideally both anterior and posterior structures. Although replacement was perceived as a compromise given the removal of an anatomically intact valve, it has since become the primary approach recommended in current clinical guidelines due to its favorable outcomes over reparative attempts, which often carry a high recurrence risk.

Throughout the years, numerous reports documenting reparative experiences have been published, though no randomized comparative study against medical therapy has been conducted. Observational studies have shown no survival benefit associated with isolated surgical interventions targeting the mitral valve. As a result, surgery holds a Class IIb indication in current guidelines for isolated mitral repair, except in cases of concomitant revascularization (Class I if LVEF >30%, Class IIa if LVEF <30%).

This scientific gap paved the way for structural interventional techniques, leading to the development of several devices targeting the mitral leaflet free edge and annulus. Abbott® MitraClip® and Edwards® Pascal® mimic the Alfieri technique, originally described for organic or primary mitral pathology and certain functional cases, such as those related to hypertrophic cardiomyopathy (SAM). Although these devices do not affect the annulus or chordal-papillary apparatus, clinical trials like COAPT (LVEF 20-50%, LVEDD <70 mm) have shown favorable outcomes against medical therapy, with COAPT now reporting 5-year results, previously discussed on this blog. In contrast, similar success was not observed in MITRA-FR (LVEF 15-40%), which allowed greater ventricular dilation without selection criteria, potentially explaining the absence of therapeutic efficacy.

Other devices, which target the annulus either directly (Edwards® Cardioband®, Mitraling®, Boston® Millipede®, and ANCORA® AccuCinch®) or indirectly via the coronary sinus (Carillon®, among others), remain in early clinical stages and lack robust evidence. Multimodal procedures combining these techniques are still rare, though likely to increase. Following the COAPT findings, edge-to-edge therapy has achieved a Class IIa recommendation in recent European guidelines.

Study by Okuno et al.
Okuno et al. present a pioneering study comparing outcomes between surgical (isolated restrictive annuloplasty) and percutaneous edge-to-edge intervention for functional mitral regurgitation. This retrospective analysis involved consecutive patients from two Swiss centers, with propensity score matching. After matching, each group consisted of 101 patients from the 199 and 222 patients who underwent percutaneous and surgical intervention, respectively. This high adjustment rate underscores significant preprocedural differences, with intervention patients generally presenting more comorbidities (age, EuroSCORE II, diabetes mellitus) and advanced cardiac disease (AF, severe pulmonary hypertension, previous MI, or revascularization). Although there were no significant pre- and post-adjustment differences, this highlights the study’s limited statistical power to detect group differences.

Mortality rates showed no significant difference either perioperatively or at 2-year follow-up (23-24%). However, recurrence of significant mitral regurgitation (grade 2+ or higher) was notably lower in the surgical group at 2 years (13.5% vs. 40.4%). Furthermore, LVEF improvement was more pronounced with surgery (+10.1% for surgery vs. -1.3% for intervention), as was functional class improvement (NYHA III or IV, 13.3% vs. 29.5%).

The authors conclude that despite the absence of a 2-year mortality difference, surgical intervention demonstrated superior outcomes in terms of mitral regurgitation recurrence and reverse remodeling, which may translate into enhanced functional class and survival in longer follow-ups.

COMMENTARY:

Okuno et al. present one of the few comparative experiences between mitral valve repair surgery and percutaneous edge-to-edge therapy for functional mitral regurgitation. The first comparable data emerged from a subgroup analysis in the EVEREST trial, which showed no significant differences at 3 years, though the edge-to-edge therapy was in early development, and the surgical alternative included a heterogeneous mix of repair and prosthetic replacement cases. Although Okuno’s study is retrospective, it opens the door for future randomized trials that could redefine clinical guideline indications. Additionally, it allows for the highlighting of specific findings, discussed below.

Firstly, this study uniquely correlates improved mitral regurgitation recurrence with LVEF improvement, a correlation not clearly demonstrated in the COAPT study. However, many patients in these groups underwent revascularization, leaving open the question of the relative contributions of mitral coaptation restoration versus revascularization (surgical or percutaneous) to LVEF improvement and consequent valvular function preservation.

Secondly, the study’s technical success rates reflect real-world practice, with a mild or no postprocedural residual regurgitation rate of 72% for the percutaneous approach. This was significantly lower than the 96-98% success rates reported in COAPT and MITRA-FR studies. Though success rates vary by criteria, the study achieved at least a one-grade reduction in mitral regurgitation for 92% of patients in both approaches, likely the criterion used in clinical trials. Furthermore, COAPT findings suggested a lack of prognostic benefit for achieving residual regurgitation levels of 0/1+ compared to 2+ or higher, while multiple surgical studies have emphasized the prognostic importance of achieving optimal repair results in terms of both recurrence and survival.

The repair technique in this study was highly standardized, although other authors suggest the superiority of “double repair,” which combines annular approaches with chordal-papillary apparatus interventions to reduce traction forces. Prosthetic replacement with complete subvalvular apparatus preservation may be preferable in cases where suboptimal repairs yield 2+ postprocedural regurgitation.

It is desirable that studies like Okuno’s continue to shed light on this debate, paving the way for larger-scale studies (from registries and clinical trials) and future meta-analyses. In the race to position devices for functional mitral regurgitation intervention, pseudoevidence and biased standards should not overshadow the honesty, prudence, and independence that surgical practice has long respected. Adequate power and follow-up will be essential to detect differences and draw conclusions that, until then, remain speculative. If guidelines drive indications prematurely, it may result in ethical violations where patient interests serve commercial ends. Through diligent work, case-by-case discussion, research, and critical analysis, the future remains in our hands.

REFERENCE:

Okuno T, Praz F, Kassar M, Biaggi P, Mihalj M, Külling M, et al. Surgical versus transcatheter repair for secondary mitral regurgitation: A propensity score-matched cohorts comparison. J Thorac Cardiovasc Surg. 2023 Jun;165(6):2037-2046.e4. doi: 10.1016/j.jtcvs.2021.07.029.