Mitral Regurgitation: When M-TEER Boosts Systolic Flow in Atrial Forms

The challenge of hemodynamic assessment after M-TEER

Transcatheter edge-to-edge mitral repair (M-TEER) is an established therapeutic option for secondary mitral regurgitation (SMR). However, identifying patients who derive the greatest clinical benefit remains complex: left ventricular ejection fraction (LVEF), conventionally used, often underestimates true ventricular dysfunction as it is biased by the regurgitant flow. In this context, forward stroke volume (FSV), measured at the left ventricular outflow tract, emerges as a potentially more accurate hemodynamic marker, although its specific clinical relevance following M-TEER is not yet clearly defined.

Objectives and challenges of the study

The objective of this retrospective single-center study was to evaluate the impact of M-TEER on FSV by comparing two distinct phenotypes: atrial secondary MR (aMR) and ventricular secondary MR (vMR). Researchers analyzed a cohort of 103 patients (60 vMR, 43 aMR) to identify predictors of significant FSV improvement (defined as an increase > 10% at 4 weeks) and to determine whether this early hemodynamic response correlates with long-term clinical outcomes. The study tests the hypothesis that SMR etiology and baseline flow influence the capacity for forward flow restoration, and evaluates whether this change constitutes a reliable prognostic marker for survival and hospitalizations at two years.

Methodology: Evaluation of the hemodynamic response post-M-TEER

This retrospective single-center study involved a cohort of 103 patients with moderate-to-severe or severe secondary mitral regurgitation (MR). All participants underwent a transcatheter edge-to-edge mitral repair (M-TEER) procedure.

The population was segmented into two groups according to the secondary MR phenotype:

• Ventricular MR (vMR): n = 60 patients.
• Atrial MR (aMR): n = 43 patients.

The central parameter, forward stroke volume (FSV), was quantified by echocardiography via flow measurement in the left ventricular outflow tract (LVOT). Assessments were performed at baseline (pre-procedure) and during a short-term follow-up at 4 weeks post-intervention. Procedural success was defined by a residual MR grade ≤ II.

Statistical analysis included multivariate models to identify predictors of a significant FSV improvement, set at a threshold > 10%. Finally, long-term clinical outcomes were documented over a 2-year period, including all-cause mortality and hospitalizations for heart failure, in order to compare "responder" and "non-responder" patients in terms of FSV.

Study results: Hemodynamic divergence between atrial and ventricular MR

Procedural success, defined as a mitral regurgitation (MR) grade ≤ II, was achieved in almost the entire cohort: 95% for patients with ventricular MR and 100% for those with atrial MR.

Evolution of forward stroke volume (FSV)

The 4-week post-procedure analysis reveals a distinct hemodynamic response depending on the MR etiology. While the FSV remains stable in the ventricular group, a significant increase is observed in the atrial group.

Predictors of FSV improvement

Multivariate analysis identified two independent factors predicting an improvement in FSV of more than 10%:

• Atrial etiology of MR: Odds Ratio (OR) of 5.12 (p = 0.048).
• Low baseline FSV: OR of 0.36 per 10 ml/m² increment (p = 0.002), suggesting that patients with a lower initial flow rate benefit from a more pronounced hemodynamic gain.

Impact on long-term clinical results

Despite the hemodynamic changes observed, the study does not demonstrate a direct correlation between the improvement in FSV and the clinical prognosis over a 2-year follow-up:

• Functional status: No significant difference was noted between "responder" patients (FSV gain) and "non-responders" regarding the residual MR grade or functional status.
• Clinical events: Early increase in FSV is not associated with a reduction in all-cause mortality or a decrease in hospitalizations for heart failure.

These data suggest that while M-TEER effectively restores forward flow in atrial MR, this response reflects an immediate hemodynamic adaptation rather than a prognostic marker of long-term survival.

Clinical analysis: a differentiated hemodynamic response

The results of this single-center study highlight a fundamental divergence between secondary mitral regurgitation (SMR) of atrial and ventricular origin. While M-TEER allows for a significant improvement in forward stroke volume (FSV) in patients suffering from an atrial etiology (increasing from 60.5 ± 21.7 to 66.8 ± 19.6 ml; p = 0.037), it remains without notable effect on forward flow in the ventricular etiology (49.4 vs 49.5 ml).

Key finding: although atrial etiology (OR 5.12) and a low baseline FSV are independent predictors of flow improvement, this early hemodynamic gain does not translate into a reduction in mortality or hospitalizations for heart failure at two years. This observation is consistent with the cited COAPT study data, where FSV also did not increase overall after the procedure. This suggests that the improvement in FSV reflects a post-procedural hemodynamic adaptation rather than a true prognostic marker of survival.

Limits and perspectives for practice

The study presents clear methodological limitations: a retrospective design, a single center, and a modest sample size (n=103). Furthermore, the lack of correlation between the increase in FSV and the improvement in the patients' functional status indicates that the technical success of the repair does not necessarily guarantee a proportional clinical benefit in the short term.

For the cardiologist and the surgeon, these data highlight the importance of initial phenotyping. While M-TEER restores forward flow more effectively in atrial MR, the management of ventricular MR remains complex, as valvular correction is not always sufficient to compensate for the underlying systolic dysfunction of the left ventricle.

Summary of results

This retrospective study of 103 patients demonstrates that M-TEER significantly increases forward stroke volume (FSV) only in atrial secondary MR (60.5 ± 21.7 vs 66.8 ± 19.6 ml, p=0.037), while it remains unchanged in ventricular MR (p=0.960). Although atrial etiology (OR 5.12) and low baseline FSV predict a hemodynamic response (>10% gain), this early improvement at 4 weeks is not correlated with a reduction in mortality or hospitalizations for heart failure at 2 years.

In concrete terms, for the practitioner:

• Distinguish the phenotypes: Expect a real forward flow gain in your patients with atrial MR, whereas M-TEER does not modify the FSV in ventricular forms.
• Manage prognostic expectations: Do not consider post-procedure FSV improvement as a survival indicator; it reflects local hemodynamic adaptation rather than a long-term clinical benefit.
• Identify responders: Patients with low baseline FSV are the best candidates for achieving immediate hemodynamic gain following repair.

Technical lexicon of the study

M-TEER (Transcatheter edge-to-edge mitral valve repair): Percutaneous mitral valve repair technique consisting of bringing the valve leaflets together using a clip to reduce regurgitation.

Forward Stroke Volume (FSV): Antegrade systemic stroke volume, measured in this study at the left ventricular outflow tract (LVOT) to assess the actual cardiac output to the aorta.

Atrial secondary mitral regurgitation (atrial MR): A form of secondary mitral regurgitation characterized by dilation of the left atrium and the mitral annulus, typically occurring in patients with preserved ventricular systolic function.

Ventricular secondary mitral regurgitation (ventricular MR): Regurgitation related to a structural or functional abnormality of the left ventricle (remodelling, dysfunction), leading to a failure of leaflet coaptation.

LVOT (Left Ventricular Outflow Tract): Left ventricular outflow tract; anatomical zone through which blood flows to the aortic valve, used to precisely quantify the FSV by Doppler.

Procedural success: Technical evaluation criterion defined in this study by obtaining a residual mitral regurgitation grade less than or equal to II (MR ≤ II) after the procedure.

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