Simplified Heart Score Predicts Risk in Dogs With Preclinical Mitral Valve Disease

Risk Stratification Using Mitral INsufficiency Echocardiographic Score 2 in Dogs With Preclinical Mitral Valve Disease

Tommaso Vezzosi, Giovanni Grosso, Liva Vatne, Francesco Porciello, Elena Dall’Aglio, Carlo Guglielmini, Helena Broch, Dave Dickson, Marta Croce, Valentina Patata, Federica Marchesotti, Rosalba Tognetti, Mark Rishniw, Oriol Domenech

Background

Myxomatous mitral valve disease (MMVD) is the most common acquired cardiac disease in dogs. Prognosis varies widely, especially in preclinical stages B1 and B2 as defined by ACVIM guidelines. The original Mitral INsufficiency Echocardiographic (MINE) score was developed to classify MMVD severity based on echocardiographic parameters. However, its applicability for outcome-based cardiac risk stratification in preclinical dogs remained untested in a large cohort. This study aimed to validate the MINE score for risk stratification and develop a simplified version—MINE score 2—to define “advanced B2” cases.

Methods

This retrospective multicenter cohort study included 749 dogs with preclinical MMVD from eight European referral centers. All dogs underwent physical examination, chest radiographs, and echocardiography. Echocardiographic variables assessed were the left atrium-to-aorta ratio (LA/Ao), normalized left ventricular end-diastolic diameter (LVIDDn), fractional shortening (FS%), and E-wave transmitral peak velocity (E-vel). Outcomes were time to first cardiac event (congestive heart failure or cardiac death). Cox proportional hazards models identified predictors of cardiac endpoints. Kaplan–Meier survival analysis compared severity classes. Dogs with incomplete follow-up (n = 50) were excluded from statistical analysis.

Results

Out of 749 dogs (median age = 11 years, median weight = 7.9 kg), 374 were classified as stage B1 and 375 as stage B2. Over a median follow-up of 781 days, 200 dogs (27%) reached the cardiac endpoint. Multivariate analysis identified LA/Ao, LVIDDn, and E-vel as independent predictors of cardiac events, while FS% was not significant. These three variables were used to develop MINE score 2, with revised cutoffs and four severity classes (mild, moderate, severe, late-stage). Median times to cardiac event decreased with increasing severity:

-Mild = 2604 days

-Moderate = 1216 days

-Severe = 718 days (p < 0.001).

Within stage B2, severe cases had significantly shorter time to cardiac event (718 days) than moderate cases (1141 days). The simplified score effectively stratified both cardiac and all-cause mortality risks.

Limitations

Limitations included the retrospective design, heterogeneous follow-up intervals, and variation in treatment regimens across centers. Approximately 6% of dogs lacked follow-up data, though sensitivity analyses suggested minimal impact on results. Some CHF diagnoses were based on clinical rather than radiographic confirmation. Inclusion of cases from referral centers may limit generalizability to general practice populations.

Conclusions

The MINE score 2, using only three echocardiographic parameters (LA/Ao, LVIDDn, E-vel), provides an effective and simplified tool for risk stratification in preclinical MMVD. It complements ACVIM staging and helps identify dogs at higher risk of progression, particularly those in stage B2 who can be classified as “advanced B2.” This tool may improve clinical decision-making and trial design in canine cardiology.

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