Mitral regurgitation: repair improves survival despite reinterventions

Clinical Context and Challenges

Mitral regurgitation (MR) is among the most prevalent valvular heart diseases, leading to significant morbidity and mortality and a major impairment in quality of life. While surgery remains the gold standard treatment, the choice between mitral valve repair (MVr), which preserves the native subvalvular apparatus, and mitral valve replacement (MVR) is still a matter of debate. Despite a theoretical preference for preserving the valvular anatomy, the long-term comparative efficacy of these two approaches remains uncertain, particularly due to the etiological diversity of MR (degenerative versus ischemic).

Objectives and Hypotheses of the Meta-analysis

The objective of this systematic review with meta-analysis, conducted according to PRISMA principles, was to rigorously evaluate and compare clinical outcomes after MVr or MVR in adult patients. The authors synthesized data from seven studies (one randomized controlled trial and six observational studies), totaling degenerative, ischemic, and mixed MR populations.

The study is based on the hypothesis that a repair strategy offers superior long-term survival and better preservation of left ventricular function (LVEF) compared to replacement. The primary endpoints tested included all-cause overall mortality and the rate of freedom from reintervention, supplemented by the analysis of perioperative mortality and the occurrence of major adverse cardiac and cerebrovascular events (MACCE).

Methodology of the meta-analysis

The authors of this publication conducted a systematic review and meta-analysis following the PRISMA guidelines. The literature search was performed on the PubMed/MEDLINE, Embase, Cochrane CENTRAL, and Scopus databases, from their inception until the date of the study's publication.

The synthesis is based on the inclusion of 7 comparative studies involving adult patients with mitral regurgitation (MR) of degenerative, ischemic, or mixed etiologies:

• 1 randomized controlled trial (RCT);
• 6 comparative observational studies.

The analysis aimed to compare two surgical strategies: mitral valve repair (MVr) versus mitral valve replacement (MVR). The primary endpoint included long-term all-cause mortality and the rate of freedom from reoperation. Secondary endpoints included perioperative mortality, left ventricular ejection fraction (LVEF), major adverse cardiac and cerebrovascular events (MACCE), as well as procedure-related complications.

Methodological rigor was assessed using the RoB 2 (for the randomized trial) and ROBINS-I (for observational studies) tools. Data were processed by a random-effects meta-analysis, expressing results via hazard ratios (HR), relative risks (RR), and mean differences (MD).

Meta-analysis results: Repair vs Replacement

This systematic review synthesized data from seven studies (1 randomized controlled trial and 6 observational studies) comparing mitral valve repair (MVr) to replacement (MVR) in adult patients with degenerative, ischemic, or mixed etiologies.

Survival and cardiac function analysis

The primary result regarding overall survival shows a Hazard Ratio (HR) of 0.74. Although this figure suggests a 26% reduction in the risk of death for the repair, the confidence interval crosses unity (1.17), making this result statistically non-significant. This lack of significance is attributed to data heterogeneity and the predominance of observational studies.

Functionally, the preservation of the subvalvular apparatus inherent in the repair technique appears to offer a clinical advantage in maintaining postoperative left ventricular ejection fraction (LVEF) compared to replacement.

Technical failures and reinterventions

• Recurrences: The authors report that the recurrence of mitral regurgitation (MR) is a weak point of the repair, particularly in patients suffering from ischemic MR.
• Reoperations: The reintervention rate is higher in the repair group for these same patients, highlighting a potential trade-off between immediate survival and long-term durability depending on the etiology.
• Major events: Procedure-related complications and major adverse cardiac and cerebrovascular events (MACCE) were evaluated as secondary endpoints, confirming overall superior perioperative safety for the repair.

Analysis of results and clinical relevance

The data compiled in this systematic review of 7 studies (1 RCT and 6 observational studies) highlight a nuanced clinical superiority of mitral valve repair (MVr) over replacement (MVR). In terms of long-term survival, the meta-analysis reports a Hazard Ratio (HR) of 0.74 (95% CI: 0.47–1.17). Although this trend suggests a protective advantage of repair, the lack of statistical significance — with the confidence interval crossing unity — mandates caution.

The advantage of repair is more pronounced in the perioperative period, with generally lower mortality and better preservation of left ventricular function (LVEF). This finding validates the mechanical benefit of preserving the subvalvular apparatus. However, a significant drawback emerges for the practitioner: the risk of reintervention. The authors of the review note that the recurrence of mitral regurgitation and the need for reoperation are more frequent after repair, particularly in cases of ischemic mitral regurgitation (IM).

Limits and perspective

The robustness of the conclusions is hindered by notable heterogeneity between the included studies and the predominance of observational data (6 out of 7 studies). This structure limits the ability to assert a definitive survival advantage, as selection biases in non-randomized studies often favor repair in the least comorbid patients. Nevertheless, the results align with the current trend in cardiac surgery favoring repair in degenerative MI, while highlighting the persistent complexity of ischemic MI where the durability of repair remains a major clinical challenge.

Summary of results

This meta-analysis of 7 studies (1 RCT, 6 observational) shows a trend toward superior survival for mitral repair (HR 0.74; 95% CI 0.47–1.17) and lower perioperative mortality. While LVEF preservation favors repair, the risk of reintervention is more pronounced, particularly in ischemic mitral regurgitation (MR).

In concrete terms, for the practitioner:

• Prioritize repair in degenerative etiologies to optimize long-term survival and left ventricular function.
• Anticipate the risk of reoperation: in ischemic MI, be vigilant about the durability of the repair given the increased risk of recurrence compared to replacement.
• Decide according to the anatomy: the clinical advantage of the repair depends on the technical probability of achieving a lasting result; do not hesitate to individualize according to the complexity of the lesion.

Technical lexicon of the study

Mitral Regurgitation (MR): Valvular pathology characterized by a leakage of the mitral valve, leading to blood reflux from the left ventricle to the left atrium during systole.

Subvalvular apparatus: Anatomical structure including the chordae tendineae and papillary muscles, essential for maintaining the geometry and contractile function of the left ventricle.

MACCE (Major Adverse Cardiac and Cerebrovascular Events): Composite endpoint used in clinical research to group major cardiovascular and cerebrovascular events (death, infarction, stroke).

Ischemic etiology: Origin of a pathology (here mitral regurgitation) linked to a reduction in myocardial blood supply, often leading to unfavorable ventricular remodeling.

Left Ventricular Ejection Fraction (LVEF): Measure of the percentage of blood expelled by the left ventricle during each cardiac contraction, a key indicator of systolic function.

Mitral valve repair (MVr): Conservative surgical technique aimed at restoring the competence of the native mitral valve without using an artificial prosthesis.

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses): A set of guidelines and methodological standards designed to ensure transparency and quality in the reporting of systematic reviews.

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