Clinical Relevance of Atriogenic Tethering in Atrial Functional Mitral Regurgitation

Functional mitral regurgitation (FMR) has been understood as a ventricular disease, secondary to systolic left ventricular (LV) dysfunction and associated remodeling. In recent years, atrial FMR (AFMR) has increasingly been recognized by imaging specialists as a distinctive clinical variant.^1,2 Unlike conventional FMR, AFMR typically arises in the context of chronic left atrial enlargement, especially associated with longstanding atrial fibrillation (AF), despite preserved or minimally impaired LV systolic function. This form of MR underlines a primary pathological mechanism involving atrial, rather than ventricular, remodeling as its primary driver.³ Within the category of AFMR, atriogenic tethering (AT) has emerged as a characteristic and anatomically distinct subset.⁴ AT involves significant displacement and restricted motion of mitral posterior leaflets, secondary to left atrial enlargement and mitral annular distortion. This phenomenon is drawing attention to clinical implications beyond representing an anatomical form. However, guidance on AT in existing valvular heart disease guidelines by the American College of Cardiology/American Heart Association (ACC/AHA) and the European Society of Cardiology/European Association for Cardio-Thoracic Surgery (ESC/EACTS) is limited.⁵ Thus, clinicians face uncertainty in applying AT findings to decision-making.

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In this context, the findings of Omori et al. derived from the large-scale observational REVEAL-AFMR registry, provide valuable insights.⁶ In this issue of the Journal, they report a prevalence of AT (24%) among patients with moderate or greater AFMR, and AT’s association with enlarged LV endsystolic dimension (LVESD) and greater left atrial diameter. Moreover, their study suggests an adverse prognostic impact of AT on clinical outcomes, including increased rates of cardiovascular death, heart failure hospitalizations, and mitral valve interventions. This study adds important new data to the clinical discussion regarding AT’s role in AFMR.

Current ACC/AHA and ESC/EACTS guidelines provide recommendations for the management of patients with chronic MR. Both guidelines support mitral valve surgery in symptomatic severe MR patients or asymptomatic patients with evidence of LV dysfunction. In addition, the ESC/EACTS guidelines specifically recognize AF and pulmonary hypertension as additional triggers for surgical consideration. These conditions commonly coexist in AFMR populations. Given that AT has emerged as a potentially significant anatomical and prognostic marker within AFMR, clinicians should consider how the presence of AT could affect their decision-making within existing guideline frameworks.

AT itself cannot immediately justify a novel surgical indication, but its presence could influence the surgical approach and technique selection. AT, driven primarily by left atrial enlargement, involves tethering of the mitral leaflets and distortion of the mitral annulus. Conventional surgical strategies such as isolated annuloplasty may not fully correct the restrictive leaflet pathology associated with prominent AT.⁷ Therefore, patients with severe AT may require more sophisticated or individualized surgical techniques. Leaflet augmentation strategies may become necessary to address leaflet tethering effectively. Specialized annuloplasty rings designed to address severe annular distortion could also provide superior long-term outcomes.⁸ Thus, surgeons and cardiologists should evaluate for AT presence during their preoperative assessment and decision-making processes, considering referral to specialized valve centers capable of applying techniques tailored for patients with significant AT.

Transcatheter edge-to-edge repair (TEER) has rapidly gained prominence as a minimally invasive therapeutic alternative for high-risk patients with severe MR. However, the specific anatomical complexities introduced by significant AT may adversely affect the procedural success and durability of TEER.⁹ The tethered leaflet anatomy observed in AT patients could limit effective leaflet grasping or result in persistent residual MR post-procedure. Current guidelines remain cautious in recommending TEER in AFMR populations, reflecting the limited clinical evidence, in anatomically challenging cases with severe AT. Given these anatomical concerns, prospective studies specifically targeting AT patients undergoing TEER are needed. Such studies could define the anatomical predictors of procedural success or failure, inform patient selection criteria, and guide future development of dedicated transcatheter technologies optimized for AT anatomy.

Due to these considerations and to help clinicians better understand how AT might influence clinical decisions within the current guideline frameworks, I summarize the relevant guideline recommendations and additional considerations specifically applicable to patients with AT (Table).

Table.

Guideline Recommendations and Special Considerations for AT

Guideline recommendation	Class	Special considerations for AT
Severe MR, symptomatic	I	AT may necessitate leaflet augmentation or advanced annuloplasty
Severe MR, asymptomatic, LVEF ≤60% or LVESD ≥40 mm	I	AT may prompt earlier surgical intervention due to rapid MR progression
Severe MR, asymptomatic, with AF or significant pulmonary hypertension	IIa	AT may require early surgical consideration
Moderate MR undergoing other cardiac surgery	IIa	AT may increase the risk of postoperative MR progression
TEER for high-risk symptomatic MR patients	IIa/IIb	AT may compromise procedural success rates and TEER durability

AF, atrial fibrillation; AT, atriogenic tethering; LVEF, left ventricular ejection fraction; LVESD, left ventricular endsystolic diameter; MR, mitral regurgitation; TEER, transcatheter edge-to-edge repair.

Several important limitations must be considered when interpreting these findings. First, the study was retrospective and observational in nature, inherently introducing potential biases. Patients initially diagnosed with moderate or moderate-to-severe MR and AT may have experienced rapid progression to severe MR during follow-up, prompting earlier surgical interventions and thus confounding the outcome analyses. Without serial imaging data, it remains unclear how MR severity and AT morphology evolved in patients initially managed conservatively. Additionally, nearly all patients in this study had concomitant AF, a condition already recognized as a potential surgical indication according to ESC/EACTS guidelines. Therefore, the higher surgical rate observed among AT patients might partly reflect existing guideline-based recommendations rather than the independent clinical impact of AT itself. Given these considerations, the current findings should be viewed as hypothesis-generating. Prospective longitudinal studies with detailed serial echocardiographic assessments, ideally using randomized or carefully matched cohorts, are required to clarify how AT influences MR progression, surgical timing, and patient outcomes. Additionally, randomized trials comparing different surgical or transcatheter approaches in patients with significant AT would offer critical insights, potentially enabling its formal integration into future clinical guidelines.

In conclusion, Omori et al. contribute valuable preliminary insights regarding AT’s clinical relevance in patients with AFMR. However, several limitations (e.g., potential selection bias and the absence of detailed longitudinal follow-up imaging data) remain barriers to interpretation. Comprehensive prospective studies, ideally involving randomized or carefully matched cohorts and serial echocardiographic assessments, are essential before AT can be integrated into formal guidelines or routine clinical decision-making algorithms.

Conflicts of Interest

The authors declare no conflicts of interest related to this work.

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