Selected echocardiographic variables change more rapidly in dogs that die from myxomatous mitral valve disease

OBJECTIVES: To determine if echocardiographic measurements change at a greater rate in dogs with myxomatous mitral valve disease (MMVD) that die of cardiac mortality.

ANIMALS: Client-owned dogs (n = 242) with MMVD of varying severity were recruited from first opinion private practice. Only dogs which died during the study period (n = 102) were included in statistical analyses.

METHODS: Prospective cohort study comparing the rate of change of echocardiographic variables between dogs that experienced cardiac mortality and those that experienced non-cardiac mortality. Measurements were repeated approximately every 6 months and repeated measures linear models were constructed to estimate the rate of change of each variable over time.

RESULTS: Left ventricular (LV) end-diastolic diameter, normalized for body weight (LVEDDN) increased over time in both mortality groups. LV end-systolic diameter, normalized for body weight (LVESDN), LV end-diastolic diameter to LV free wall thickness in diastole (LVEDD/LVFWd) ratio, E wave velocity, E- to A-wave velocity ratio and left atrial to aortic root diameter ratio all increased over time in the cardiac mortality group, but did not change in the non-cardiac mortality group. MR velocity decreased over time in the cardiac mortality group but did not change in the non-cardiac mortality group. Tricuspid regurgitation jet velocity increased over time in both mortality groups. A wave velocity and fractional shortening did not change over time in either mortality group.

CONCLUSIONS: Serial echocardiographic examination every 6-12 months is useful to identify dogs with progressive MMVD that are at increased risk of cardiac mortality.