Causes and mechanisms of isolated mitral regurgitation in the community: clinical context and outcome

Summary

This community-based cohort study characterised the aetiology and mechanisms of moderate-to-severe isolated mitral regurgitation in 727 patients (mean age 73 years) diagnosed between 2000–2010 in Olmsted County, Minnesota. Functional mitral regurgitation predominated (65%), subdivided into left ventricular remodelling-related (38%) and atrial dilatation-related (27%) forms, with the remainder organic (32%). The three subgroups displayed marked clinical heterogeneity: functional mitral regurgitation with left ventricular remodelling carried the highest excess mortality risk (3.45-fold) and 5-year heart failure incidence (83%), whilst organic mitral regurgitation underwent more frequent surgical intervention (37%) despite lower heart failure risk. The findings suggest substantial undertreatment of functional mitral regurgitation subtypes despite their significant morbidity and mortality burden.

UK applicability

The epidemiological patterns and clinical outcomes reported reflect an ageing community population and may be broadly applicable to UK primary and secondary care settings, though surgical intervention thresholds and practices may differ between health systems. The emphasis on undertreatment in functional mitral regurgitation warrants consideration in NHS commissioning and clinical guideline development.

Key measures

Mitral regurgitation type (functional vs. organic), mechanism classification (Types I–IIIb), age, sex, atrial fibrillation prevalence, ejection fraction, regurgitant volume, excess mortality risk ratio, 5-year heart failure incidence, mitral surgery rates

Outcomes reported

The study classified mitral regurgitation aetiology and mechanisms in 727 community-dwelling patients and compared clinical characteristics, heart failure incidence, mortality risk, and surgical intervention rates across aetiological subgroups over follow-up.

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