Research in context
Evidence before this study
We searched the Cochrane Library and PubMed for publications about the prevalence and outcomes of isolated moderate to severe mitral regurgitation between Jan 1, 1990, and June 1, 2016, using the search terms “epidemiology”, “prevalence”, “outcomes”, “mitral insufficiency”, “regurgitation”, and “isolated”. Mitral regurgitation is generally considered the most common heart valve disorder worldwide, but only a few studies have reported on its epidemiology. In particular, outcome after diagnosis, which has been analysed previously only in selected populations, remains undefined in the community setting. Although mitral surgery is established as the only guideline-recommended treatment for moderate to severe mitral regurgitation, access to care and treatment might be insufficient in some settings. However, access to care and treatment for isolated mitral regurgitation has not been evaluated in an entire community with state-of-the-art facilities, good access to treatment, and high availability of specialised providers, or over the long-term. In summary, prevalence, survival, heart failure rates, and surgical outcomes of rigorously defined isolated mitral regurgitation (diagnosed by Doppler echocardiography) over the long-term, in an entire community with no or minimal impediment to access to care, is unknown; therefore, the unmet need for treatment for this heart valve disorder remains uncertain.
Added value of this study
We analysed a cohort of patients with isolated mitral regurgitation in Olmsted County, MN, USA, that included all community-wide consecutive cases diagnosed, to define the prevalence of the disorder and—most importantly—to assess its management and outcomes across the community and in the long term. Because this community has modern facilities, diagnostic methods, expertise, and cardiac surgery easily accessible, it provides an ideal setting to ascertain whether mitral regurgitation therapeutic needs are met. In this context, we can report a high community prevalence of isolated mitral regurgitation. We also found that from all diagnosed cases, isolated moderate or severe mitral regurgitation is associated with excess mortality compared to that expected in the same county, both overall and in all subsets of patients, even those who seem to have the most benign types of the disorder. Similarly, heart failure is very frequent in all subsets of patients with mitral regurgitation, even in those without any other predisposing factor or comorbidity. Most importantly, long-term outcome analysis showed that despite all available facilities and expertise, only 15% of patients ultimately underwent surgical correction of the mitral regurgitation. It is particularly notable that women were operated on less than half as often as men. Hence, for the first time, we show that in a community with very well-equipped medical facilities and good access to treatment, moderate-to-severe isolated mitral regurgitation is common, and is associated with a high incidence of heart failure, and severe excess mortality, and is substantially undertreated.
Implications of all the available evidence
All evidence, especially our lifelong population-based data, point towards a substantial unmet need for treatment of mitral regurgitation, which contrasts with the high excess mortality and high frequency of heart failure, with few patients receiving the only treatment available (surgery) and represents a call for action. Beyond the necessary education of care providers regarding medical knowledge and clinical guidelines for mitral regurgitation, referral of patients with the disorder to cardiology teams for decision-making, integrating all clinical information and therapeutic approaches available, is a critical step for these patients to obtain access to care. Simultaneously, new approaches to treatment of mitral regurgitation in all subsets of patients warrant development and testing in appropriate clinical trials.