C26 - Mitral Regurgitation Severity Index Predicts Outcome in Diverse Populations of Canine Myxomatous Mitral Valve Disease

Abstract: Background – Outcome is variable in dogs with preclinical myxomatous mitral valve disease (MMVD). Mitral regurgitation severity index (MRSI) combines 3 variables (heart rate [HR], age, and left atrium to aorta ratio [LA:Ao]) into a single index that appears to have prognostic utility.



Hypothesis/Objectives – MRSI will predict time to first-onset congestive heart failure (CHF) and all-cause mortality in dogs with MMVD stage B2 and will have superior prognostic utility compared to its constituent variables alone.



Animals – 235 client-owned dogs with MMVD Stage B2 from 3 diverse populations.



Methods – Retrospective study pooling data from 3 study populations. MRSI was calculated as: ([HR]/120 x LA:Ao x [age in years]/10 x 100). Cox proportional hazard modeling and time-dependent receiver-operator characteristic curves quantified prognostic performance of MRSI, HR, LA:Ao, and age. The maximally selected rank statistics determined the optimal MRSI cutoff.



Results – MRSI > 156 was predictive of time to CHF (median 407 days for MRSI > 156 vs. 1404 days for MRSI ≤ 156; AUC 0.68; hazard ratio 3.05 [95% CI 1.9-4.9]; p < 0.001). MRSI > 173 was predictive of all-cause mortality (median survival 868 days for MRSI > 173 vs. 1843 days for MRSI ≤ 171; AUC 0.63; hazard ratio 3.98 [95% CI 2.3-6.9]; p < 0.001). MRSI showed superior predictive value compared to HR, LA:Ao, or age.



Conclusions and clinical importance – MRSI was predictive of outcome and outperformed each index component alone. MRSI shows potential as a clinically useful prognostic tool in MMVD stage B2.