Associations of C-reactive protein and neutrophil-to-lymphocyte ratio with cardiac remodeling, pulmonary hypertension, and survival outcomes in dogs with myxomatous mitral valve disease.

Background and Aim: Myxomatous mitral valve disease (MMVD) is the most common cardiac disorder in dogs and is frequently associated with progressive cardiac remodeling and pulmonary hypertension (PH). Increasing evidence suggests that systemic inflammation contributes to disease progression; however, the clinical relevance of inflammatory biomarkers in relation to cardiac structural changes and outcomes remains incompletely understood. This study aimed to evaluate the associations between C-reactive protein (CRP), neutrophil-to-lymphocyte ratio (NLR), cardiac remodeling indices, PH, and survival outcomes in dogs with MMVD. Materials and Methods: A retrospective cohort study was conducted using medical records of 94 client-owned dogs diagnosed with MMVD between 2023 and 2025. Dogs were classified according to the American College of Veterinary Internal Medicine (ACVIM) stages (B1-D). Echocardiographic parameters, including left atrial (LA) volume, LA/Ao ratio, and left ventricular internal diameter, were assessed alongside PH status determined by tricuspid regurgitation velocity. Hematologic parameters and serum CRP concentrations were analyzed. Correlation, regression, receiver operating characteristic (ROC), and survival analyses were performed to determine associations and prognostic value. Results: LA enlargement was observed in 84.0% of dogs and increased with disease severity. CRP and NLR showed weak but statistically significant positive correlations with indexed LA volume (CRP: r = 0.31, p < 0.01; NLR: r = 0.29, p < 0.05). Neither biomarker demonstrated a significant association with PH. Indexed LA volume, rather than inflammatory biomarkers, was more strongly associated with echocardiographic indicators of PH risk. CRP exhibited moderate diagnostic performance for PH (area under the curve = 0.7517, p < 0.001), whereas NLR showed poor discrimination. Survival analysis revealed that dogs with elevated CRP levels and concurrent PH had significantly reduced survival probabilities. Although NLR increased with disease progression, its prognostic utility remained limited. Conclusion: Systemic inflammatory biomarkers, particularly CRP, are modestly associated with cardiac remodeling and survival in dogs with MMVD but are not reliable predictors of PH. Echocardiographic indices, especially LA remodeling, remain superior indicators of disease severity and PH risk. While CRP may provide adjunctive prognostic value, its clinical application should be interpreted cautiously alongside established imaging parameters.