Long-Term Survival Outcomes in Asymptomatic Patients with Degenerative Mitral Regurgitation: Insights from a 25-Year Prospective Cohort Study

Highlight

This landmark 25-year cohort study demonstrates the prognostic importance of baseline quantified mitral regurgitation (MR) severity in asymptomatic patients and supports surgical intervention in patients with upper-moderate MR (effective regurgitant orifice [ERO] 30-39 mm²) to improve long-term survival outcomes.

Study Background

Degenerative mitral regurgitation is a common valvular heart disease characterized by the backward flow of blood from the left ventricle to the left atrium due to dysfunction of the mitral valve. Although current clinical guidelines recommend considering surgical repair for patients with severe MR even if asymptomatic, there remains uncertainty regarding the prognosis and optimal timing of surgery in those with moderate MR. The natural history and mortality risk associated with graded MR severity have not been robustly elucidated over extended periods, especially in patients without symptoms at baseline. Understanding the long-term impact is critical for refining risk stratification and optimizing timing of interventions.

Study Design

This was a single-center, prospective cohort study conducted at the Mayo Clinic, Rochester, Minnesota. The study enrolled 449 asymptomatic patients with holosystolic degenerative MR between January 1991 and November 2000. Baseline MR severity was quantified using effective regurgitant orifice area (ERO), a reliable echocardiographic metric representing the cross-sectional size of the regurgitant flow. Patients were categorized into three groups according to ERO: <20 mm² (mild), 20-39 mm² (moderate), and ≥40 mm² (severe). Medical management was initially applied, and surgical repair was performed as indicated during follow-up, which extended through May 2025, with a median follow-up of 26 years (interquartile range 14-29 years) and a maximum of 34 years.

The primary outcome was all-cause mortality, assessed in relation to baseline ERO and receipt of mitral valve surgery. Cox proportional hazards models adjusted for relevant cardiovascular risk factors were utilized to estimate survival impacts.

Key Findings

The cohort’s mean age was 64 years, and 62% were male. At baseline, 28% had ERO <20 mm², 28% had 20-39 mm², and 43% had ≥40 mm². During the extensive follow-up period, 57% (254 patients) underwent mitral valve surgery. The cumulative incidence of surgery at 10 years varied substantially by ERO category: 18% for <20 mm², 64% for 20-39 mm², and 88% for ≥40 mm², reflecting clinical decision-making aligned with severity.

Among patients managed medically, survival decreased progressively with increasing baseline ERO: the 5-year survival rates were 88% for ERO <20 mm², 72% for 20-39 mm², and 55% for ≥40 mm² (P=0.01). Multivariable analysis confirmed that higher ERO independently increased mortality risk, with an adjusted hazard ratio of 2.53 per interquartile range increase (95% CI, 1.30-4.93; P=0.01).

Importantly, when including postsurgical follow-up, the survival advantage of surgery became more apparent as baseline ERO increased, with a statistically significant interaction starting at an ERO above 30 mm² (interaction P=0.04). Patients with upper-moderate MR (30-39 mm²) who underwent surgery showed significantly improved long-term survival compared to those managed medically, underscoring a potential benefit of earlier surgical intervention beyond the traditionally defined severe MR threshold.

Expert Commentary

This study provides compelling long-term data addressing a critical gap in MR management, highlighting that risk stratification based on quantitative ERO is clinically meaningful. The findings challenge the conventional dichotomous classification of MR severity and suggest nuanced evaluation of the upper range of moderate MR. Surgical intervention in this group may prevent progressive cardiac remodeling and reduce mortality.

Limitations include the single-center design and the potential for selection bias given referral patterns at a tertiary center. Additionally, evolving surgical techniques and perioperative care over three decades could influence outcomes. Nonetheless, the prospective design and long follow-up strengthen the evidence base for clinical decision-making.

Conclusion

This extensive 25-year follow-up demonstrates that increasing baseline ERO in asymptomatic patients with degenerative MR portends higher mortality under medical therapy. The data support reconsideration of current guidelines to contemplate earlier surgical intervention for patients with upper-moderate MR (ERO 30-39 mm²), as they may derive significant long-term survival benefits. Future research should aim to integrate these findings into risk models and examine quality-of-life outcomes to further guide personalized treatment strategies.

Funding and ClinicalTrials.gov

The study was conducted at the Mayo Clinic without specific funding disclosures. The clinical trial registration is not specified.

References

1. Karadzha A, Schaff HV, Lahr BD, Nkomo VT, Banivaheb B, Enriquez-Sarano M. Twenty-Five-Year Follow-Up of Quantified Mitral Regurgitation. JAMA Cardiol. 2026 Jul 29. PMID: 42525396.

2. Bonow RO, et al. 2020 ACC/AHA Guideline for the Management of Patients With Valvular Heart Disease. Circulation. 2020;143(5):e72-e227.

3. Goldman ME, et al. Quantitative assessment of mitral regurgitation by Doppler echocardiography. Circulation. 1986;74(2):256-67.