The Natural History of Atrial Functional Mitral Regurgitation

Echocardiographic cardiac damage classification and clinical outcomes in atrial functional mitral regurgitation

BACKGROUND

Atrial functional mitral regurgitation (AFMR) arises from left atrial (LA) dilation, commonly associated with atrial fibrillation, and leads to progressive cardiac damage. This study evaluated the prognostic value of a novel echocardiographic cardiac damage classification system for patients with moderate or severe AFMR.

METHODS

In a retrospective multicentre study, 1007 patients with AFMR were stratified into four groups based on echocardiographic findings: group 1, LA damage (dilation); group 2, left ventricular damage (reduced ejection fraction and/or dilation); group 3, right heart damage (tricuspid regurgitation and/or pulmonary hypertension); and group 4, combined left and right heart damage. The primary outcome was a composite of all-cause death, heart failure hospitalisations and mitral valve (MV) interventions over a median follow-up of 3.0 years.

RESULTS

The cohort's mean age was 78±10 years, with 56% female. Event rates for the primary outcome were progressively higher across groups 1-4 (31.0%, 38.0%, 46.3% and 57.2%, respectively; p<0.001). After multivariable adjustment, group 4 was associated with a significantly higher risk of the primary outcome compared with group 1 (HR 1.65, 95% CI 1.29 to 2.11, p<0.001). This classification consistently stratified risks for individual components of the composite endpoint, particularly in patients without MV intervention.

CONCLUSIONS

A cardiac damage classification system based on echocardiographic parameters provides prognostic insights in patients with AFMR, identifying subgroups at higher risk of adverse outcomes. Future studies are needed to validate its use in guiding therapeutic decisions.

Atrial and ventricular functional mitral regurgitation: prevalence, characteristics, outcomes, and disease progression

AIMS

Limited data exist on the natural history of functional mitral regurgitation (FMR), including atrial (AFMR), ventricular (VFMR), and dual FMR. This study examined the prevalence, characteristics, outcomes, and progression of these FMR subtypes.

METHODS AND RESULTS

Consecutive patients with ≥mild to moderate FMR were included and classified as AFMR, VFMR, or dual FMR. AFMR is characterized by left atrial enlargement, while VFMR involves left ventricular enlargement or reduced left ventricular ejection fraction. Dual FMR combines features of both. Clinical outcome was all-cause mortality and heart failure (HF) hospitalization. Echocardiographic outcome was the progression from mild-moderate/moderate to severe FMR and from AFMR/VFMR to dual FMR. Of 22 814 patients, AFMR, VFMR, and dual FMR were identified in 39%, 14%, and 47%, respectively. Most (84%) had mild-moderate to moderate FMR. Over a median clinical follow-up of 4.7 years, dual FMR has the highest risk of all-cause mortality and HF hospitalization. Compared with AFMR, patients with VFMR have a higher incidence of all-cause mortality (adjusted HR = 1.73, 95%CI 1.54-1.94, P < 0.001) and HF hospitalization (adjusted HR = 1.23, 95%CI 1.15-1.32, P < 0.001). In the serial cohort with 2.4 (1.0-4.9) years echocardiogram follow-up, VFMR was associated with a 1.51-fold and 3.08-fold increase in the risk of progressing to severe FMR and dual FMR than AFMR (both P < 0.001). Sensitivity analyses did not change these findings.

CONCLUSION

AFMR and VFMR have significant differences in survival and disease progression. Dual FMR is a common and distinct disease process that occurs in the progression of AFMR or VFMR and is associated with a poor prognosis.

Atrial Functional Mitral Regurgitation: Definition, Mechanisms, and Treatment Perspectives

PURPOSE OF REVIEW

This review aims to explore the complex interplay between atrial functional mitral regurgitation (AFMR), atrial fibrillation (AF), and heart failure with preserved ejection fraction (HFpEF). The goal is to define these conditions, examine their underlying mechanisms, and discuss treatment perspectives, particularly addressing diagnostic challenges.

RECENT FINDINGS

Recent research highlights the rising prevalence of AFMR, now accounting for nearly one-third of significant mitral regurgitation cases. Advances in percutaneous treatment options have improved management for vulnerable HFpEF patients, but long-term outcomes remain unclear, and symptom relief is inconsistent. AF and HFpEF share the left atrium as a common pathological substrate, with progressive LA remodeling contributing to AFMR. Diagnostic limitations hinder effective symptom management with current mitral valve interventions. Future research should focus on better diagnostic tools to determine the contributions of valvular disease, arrhythmia, or myocardial dysfunction to clinical outcomes, as we currently lack definitive tests to establish this connection.

Atrial Functional Mitral Regurgitation: From Diagnosis to Current Interventional Therapies

Mitral regurgitation (MR) is one of the most common valvular pathologies worldwide, contributing to the morbidity and mortality of several cardiovascular pathologies, including heart failure (HF). Novel transcatheter treatment for MR has given the opportunity for a safe and feasible alternative, to surgery, in order to repair the valve and improve patient outcomes. However, after the results of early transcatheter edge-to-edge repair (TEER) trials, it has become evident that subcategorizing the mitral regurgitation etiology and the left ventricular function, in patients due to undergo TEER, is of the essence, in order to predict responsiveness to treatment and select the most appropriate patient phenotype. Thus, a novel MR phenotype, atrial functional MR (AFMR), has been recently recognized as a distinct pathophysiological entity, where the etiology of the regurgitation is secondary to annular dilatation, in a diseased left atrium, with preserved left ventricular function. Recent studies have evaluated and compared the outcomes of TEER in AFMR with ventricular functional MR (VFMR), with the results favoring the AFMR. In specific, TEER in this patient substrate has better echocardiographic and long-term outcomes. Thus, our review will provide a comprehensive pathogenesis and mechanistic overview of AFMR, insights into the echocardiographic approach of such patients and pre-procedural planning, discuss the most recent clinical trials and their implications for future treatment directions, as well as highlight future frontiers of research in the setting of TEER and transcatheter mitral valve replacement (TMVR) in AFMR patients.