C03 - Assessing Myocardial Remodeling in Dogs with Myxomatous Mitral Valve Disease Using Cardiac Magnetic Resonance Imaging

Background: Some dogs with myxomatous mitral valve disease (MMVD) develop progressive volume overload and cardiomegaly. Histopathologic studies, but not antemortem evaluations, have demonstrated myocardial fibrosis in some of these dogs. Cardiac magnetic resonance imaging (CMR) aids in antemortem diagnosis of myocardial fibrosis in humans.

Hypothesis/Objectives: The objectives were to evaluate dogs with MMVD and healthy dogs for myocardial ischemia and fibrosis using serum biomarkers and CMR. We hypothesized that myocardial changes would be evident on both modalities in affected dogs.

Animals: Six dogs with MMVD stage B2 and six healthy dogs recruited from a hospital population.

Methods: Prospective case-control study. Dogs underwent echocardiography and serum cardiac biomarker measurement (cardiac troponin I (cTnI), galectin-3 (Gal-3)). Dogs were anesthetized for CMR, where T2 weighted images and pre- and post-gadolinium contrast T1 weighted images were acquired and analyzed on dedicated software. Data were analyzed for normality and expressed as mean±SD or median(interquartile range). Student’s t-tests or Wilcoxon rank sums tests were performed.

Results: No significant differences were observed for pre-contrast T1 values, post-contrast T1 values, and T2 values (msec) (MMVD 1171.33±52.77, 728(700-764.75), and 39.2±7.6; controls 1180.83±33.89, 711(697.5-736.5), and 42.38±12.62; p=0.72, p=0.57, p=0.61). Serum cTnI (ng/mL) was greater in MMVD dogs than controls (0.067±0.019 vs. 0.033±0.021; p=0.013). Serum Gal-3 (pg/mL) was not different between groups (MMVD 178.07±105.59, controls 305.24±123.29; p=0.08).

Conclusions and clinical importance: Myocardial fibrosis detected by CMR and Gal-3 were not more common in MMVD dogs than controls. Dogs with MMVD stage B2 may not have clinically relevant myocardial fibrosis.