Highlights
The study provides robust real-world evidence comparing transcatheter edge-to-edge repair (TEER) with medical management for Atrial Functional Mitral Regurgitation (AFMR). Key takeaways include:
- TEER was associated with a 35% reduction in the primary composite endpoint of all-cause mortality and heart failure hospitalization (HR 0.65; 95% CI 0.43-0.99).
- A 42% reduction in all-cause mortality was observed in the TEER group compared to medical therapy (HR 0.58; 95% CI 0.35-0.99).
- The clinical benefit of TEER appears heavily dependent on procedural success; patients with mild or less residual MR saw the most significant gains, while those with moderate or greater residual MR had outcomes similar to the medical therapy group.
Background: The Challenge of Atrial Functional Mitral Regurgitation
Atrial functional mitral regurgitation (AFMR) has emerged as a distinct clinical entity, primarily affecting elderly patients with long-standing atrial fibrillation (AF) and heart failure with preserved ejection fraction (HFpEF). Unlike ventricular functional mitral regurgitation (VFMR), which stems from left ventricular dysfunction and remodeling, AFMR is driven by left atrial enlargement and mitral annular dilation. This leads to insufficient leaflet coaptation despite relatively preserved left ventricular (LV) systolic function.
The management of AFMR remains clinically challenging. These patients are often elderly, frail, and carry multiple comorbidities, making them poor candidates for traditional surgical mitral valve intervention. While medical therapy, including rhythm control and diuretics, remains the standard of care, many patients continue to experience recurrent heart failure hospitalizations and high mortality rates. Until recently, the prognostic impact of transcatheter edge-to-edge repair (TEER) in this specific population was largely unknown, as major trials like COAPT focused primarily on VFMR.
Study Design and Methodology
To address this evidence gap, researchers conducted a comprehensive comparison using data from two major Japanese registries: the OCEAN-Mitral registry (patients undergoing TEER) and the REVEAL-AFMR registry (patients managed medically). The study utilized an identical definition for AFMR across both cohorts to ensure consistency.
The total cohort consisted of 1,081 patients with moderate or severe AFMR. The mean age was 80.1 years, reflecting the typical elderly demographic of this condition, and 60.5% were female. Of these, 441 patients underwent TEER, while 640 received medical treatment.
Given the non-randomized nature of the registries, the researchers employed advanced statistical methods to minimize selection bias. The primary analysis used overlap weighting based on propensity scores, which successfully yielded well-balanced characteristics across the two groups (standardized mean differences < 0.01). Sensitivity analyses included inverse probability of treatment weighting (IPTW), propensity score matching, and multivariable Cox regression to ensure the robustness of the findings.
Key Findings: Survival and Hospitalization
The primary endpoint of the study was a composite of all-cause mortality and heart failure (HF) hospitalization. The secondary endpoint focused specifically on all-cause mortality. The results demonstrated a clear advantage for the interventional approach.
Primary and Secondary Outcomes
In the propensity-weighted analysis, TEER was associated with a significantly lower incidence of the composite primary endpoint (Hazard Ratio [HR] 0.65; 95% CI 0.43-0.99; P = .044). When looking at mortality alone, the benefit was even more pronounced, with an HR of 0.58 (95% CI 0.35-0.99; P = .044). These findings suggest that reducing the regurgitant volume via TEER translates into tangible survival benefits and improved clinical stability for AFMR patients.
The Role of Procedural Success
An exploratory subgroup analysis provided critical insights into the importance of procedural quality. The researchers found that the favorable outcomes associated with TEER were largely driven by patients who achieved a residual MR grade of mild or less. In contrast, patients who were left with moderate or greater residual MR following the TEER procedure experienced event rates comparable to those in the medical treatment group. This highlights that for AFMR, as with other forms of MR, “good enough” may not be sufficient; achieving optimal coaptation is essential for altering the disease’s natural history.
Expert Commentary: Mechanistic Insights and Clinical Implications
The results of this study are significant because they suggest that mechanical correction of AFMR can improve prognosis, even in an elderly and frail population. Mechanistically, TEER addresses the pathophysiology of AFMR by reducing the effective regurgitant orifice area through the creation of a double-orifice valve, effectively compensating for the annular dilation and lack of leaflet coaptation.
From a clinical perspective, these findings may influence future guidelines. Current recommendations for AFMR have been less definitive than those for primary MR or VFMR due to a lack of comparative data. This study suggests that TEER should be considered earlier in the treatment algorithm for symptomatic AFMR patients who do not respond adequately to medical therapy. However, clinicians must weigh the potential for benefit against the patient’s overall frailty and the likelihood of achieving a high-quality procedural result.
It is also worth noting the demographic profile of the participants. The high proportion of elderly female patients in the study reflects the real-world epidemiology of AFMR and underscores the importance of including these often-underrepresented groups in cardiovascular research.
Study Limitations
Despite the use of sophisticated propensity score weighting, this study remains an observational analysis of registry data. Residual confounding by unmeasured variables—such as specific frailty indices or patient preferences—cannot be entirely ruled out. Furthermore, while the OCEAN-Mitral and REVEAL-AFMR registries provide high-quality data, they represent a specific geographic population (Japan), and the findings may require validation in other global cohorts. Finally, the study did not detail the specific medical regimens used, which could vary between centers and impact the comparative outcomes.
Conclusion
In this large-scale, propensity-matched comparison, transcatheter edge-to-edge repair was associated with lower rates of mortality and heart failure hospitalization compared with medical therapy in patients with moderate to severe atrial functional mitral regurgitation. These findings provide a strong rationale for the use of TEER in AFMR, particularly when a high degree of MR reduction can be achieved. As the population ages and the prevalence of atrial fibrillation continues to rise, TEER may become an increasingly vital tool in the management of this complex patient group.
References
1. Kaneko T, Kagiyama N, Okazaki S, et al. Transcatheter edge-to-edge repair vs medical therapy in atrial functional mitral regurgitation: a propensity score-based comparison from the OCEAN-Mitral and REVEAL-AFMR registries. European Heart Journal. 2026;47(11):1304-1314. PMID: 40629531.
2. Grayburn PA, Sannino A, Packer M. Proportionate and Disproportionate Functional Mitral Regurgitation: A New Conceptual Framework That Discusses the Role of Mitraclip in HFpEF and HFrEF. JACC: Cardiovascular Imaging. 2019.
3. Gertz ZM, Herrmann HC, Lim DS, et al. Atrial functional mitral regurgitation: mechanisms and pathophysiology. Journal of the American College of Cardiology. 2011.
