Mitral Regurgitation Severity Index: A Simple Calculation for Classification and Prognostication?

Abstract: Background. Prognosis in myxomatous mitral valve disease (MMVD) is variable. Better methods of predicting outcome would aid in communication with individual pet owners and sub-division of research cohorts. The mitral regurgitation severity index (MRSI) was originally developed by VETPROOF (Veterinary Enalapril Trial to Prove Reduction in Onset Of Failure) investigators to predict MMVD outcome. While other promising indices are now available, MRSI is appealing in its simplicity. This abstract serves as the seminal report of MRSI’s efficacy in prognosticating asymptomatic MMVD.









Hypothesis/Objectives. MRSI will predict time to CHF









Animals. 133 dogs with ACVIM Stage B2 MMVD









Methods. VETPROOF entry data from dogs randomized to either enalapril or placebo were retrospectively evaluated. Potentially useful indicators of time to onset of heart failure (CHF), including age, heart rate, and echocardiographically-determined left atrium-to-aortic ratio (LA:Ao), were used to establish MRSI, by the following equation:




MRSI = [(Age/10) x (Heart-Rate/120) x (LA:Ao)] x 100.




Kaplan-Meier survival curves and Cox proportional hazard analyses were used to evaluate the predictive ability of MRSI for time to CHF (significance, P < 0.05).









Results. MRSI, stratified at < 150, 150-249, and >249 demonstrated significant differences in time to the endpoints, thereby predicting MMVD prognosis. (Figure).









Conclusion. MRSI is easily obtained and useful in stratification and prognostication of MMVD. Studies are ongoing to test this index more rigorously in a larger cohort of dogs with MMVD, stage B2 or C. The MRSI could be modified by substituting radiographic determination of LA:Ao, making calculation and utilization of MRSI more practitioner-friendly.