Management of asymptomatic mitral regurgitation (MR) remains challenging. A long-term observational study from the Mayo Clinic presented at the AATS 2026 evaluated survival outcomes according to baseline effective regurgitant orifice (ERO) severity and examined the association between surgical intervention and long-term survival.

The cohort included 449 asymptomatic patients with holosystolic MR enrolled between 1991 and 2000. Patients were initially managed medically and subsequently followed after any mitral valve surgery over a median follow-up of 26 years. Survival analyses were stratified by baseline ERO category and adjusted for cardiovascular risk factors using Cox proportional hazards models.

Findings

• During follow-up, 254 patients (57%) underwent mitral valve surgery.
• Ten-year cumulative incidence of mitral valve surgery increased with MR severity: 18% for ERO <20 mm², 64% for ERO 20–39 mm², and 88% for ERO ≥40 mm².
• Among medically managed patients, survival declined progressively with increasing ERO category.
• Five-year survival rates under medical therapy were 88% for ERO <20 mm², 72% for ERO 20–39 mm², and 55% for ERO ≥40 mm² (P=0.010).
• In multivariable analysis of medically managed patients, increasing ERO on a continuous scale was independently associated with higher mortality risk: adjusted HR per interquartile range increase 2.53 (95% CI 1.30–4.93; P=0.010).
• When follow-up included subsequent surgical management, survival benefit associated with surgery increased with higher ERO values (interaction P=0.039).
• The apparent survival benefit from surgery began at ERO values above 30 mm².
• Among medically and surgically managed patients combined, 25-year survival was 54% for ERO ≥40 mm², 46% for ERO <20 mm², and 36% for ERO 20–39 mm².

In this long-term observational cohort of asymptomatic mitral regurgitation, increasing ERO severity was associated with excess mortality during medical management. Patients with upper-moderate MR, particularly those with ERO values between 30 and 39 mm², appeared to derive greater long-term survival benefit from surgical correction.