Quantitating Mitral Regurgitation in Clinical Trials: The Need for a Uniform Approach

There is an established relationship between the degree of mitral regurgitation (MR) and prognosis. Quantitation of MR severity guides therapeutic approaches. Inconsistent definitions and categorization of MR severity in clinical studies limit meaningful comparisons among trials and compromise development of an effective evidence base. The purpose of this study was to quantify heterogeneity in grading systems for MR severity in the contemporary literature.

This was a systematic review of randomized controlled trials and propensity score-adjusted clinical studies of mitral valve interventions (surgical or percutaneous). A total of 35 articles from 2015 to 2020 were included (15 randomized controlled trials and 20 propensity score-adjusted clinical studies).

There were 22 studies that reported MR severity in numeric categories, either values from the historical "plus" system or numeric MR grades, whereas 9 studies reported MR severity using text-only descriptive categories. Among the studies that used numeric categories, 2+ MR was defined as moderate in 64% of studies, mild in 27%, and mild-moderate in 9%, and 3+ MR was defined as moderate in 14%, moderate-severe in 52%, and severe in 14%.

There was substantial variability in MR severity definition and reporting in contemporary clinical studies of mitral valve interventions. We recommend that the historical plus numeric grading system be abandoned and that inclusion and outcome criteria in MR clinical trials be based on US and European guideline-recommended categories as none or trace, mild, moderate, and severe. Adoption of these simple recommendations will improve the consistency and quality of MR clinical trial design and reporting.