Canine degenerative mitral valve disease (DMVD) is a chronic and variably progressive condition. In dogs with DMVD, a left apical, systolic murmur is a consistent clinical finding on physical examination. Heart murmur intensity has been significantly and positively associated with echocardiographic measurements of left heart chamber size and disease severity. These findings have not been evaluated longitudinally. This study aimed to evaluate whether changes in heart murmur intensity reflect longitudinal changes in echocardiographic dimensions in a cohort of dogs variably affected by DMVD.
Clinical data were sourced from the records of dogs that had visited a research clinic on more than one occasion. The daily rate of change in the left atrial to aortic root ratio (LA:Ao) and left ventricular internal diameter in diastole normalised to bodyweight (kg) (LVIDDN) were calculated for each inter-visit interval and multiplied by 1000 to aid data handling and interpretation. Separate linear mixed effects models were constructed for the rates of change of LVIDDN and LA:Ao respectively. Murmur intensity, scored using the Levine 6-point scale, was classified according to whether it had “increased”, “decreased” or been “maintained” over each interval and was entered as an explanatory variable. Additional explanatory variables that were included in models had been recorded at the first examination in each interval. These were: patient age; breed; sex; weight; murmur grade; LVIDDN; LA:Ao; ACVIM stage; and treatment status with furosemide, pimobendan, angiotensin converting enzyme inhibitors (ACEi) and spironolactone. Post hoc estimated marginal means were calculated for categorical variables that remained significant in multivariable analyses and were entered into pairwise comparisons to determine if between group differences in the coefficient were statistically significant.
Data from 912 visits were entered from a cohort of 167 dogs. A change in murmur intensity was significantly associated with the rate of change of LVIDDN (P < 0.001) in a multivariable analysis alongside: murmur grade; patient age; breed; LVIDDN; LA:Ao and treatment status with an ACEi. A change in murmur intensity was also associated with the rate of change of LA:Ao in a separate multivariable analysis (P < 0.001) alongside: patient ACVIM stage; LVIDDN; LA:Ao; and treatment status with furosemide. The rate of change of both echocardiographic measurements was greatest when murmur intensity increased (LVIDDN: b = 0.472 ± 0.066; LA:Ao: b = 0.818 ± 0.074), followed by intervals where murmur intensity did not change (LVIDDN: b = 0.176 ± 0.055; LA:Ao: b = 0.564 ± 0.060), and lowest when murmur intensity decreased (LVIDDN: b = -0.150 ± 0.077; LA:Ao: b = 0.241 ± 0.089). All pairwise comparisons of coefficients were highly significant (P < 0.001).
Royal Veterinary College
Jenny Wilshaw graduated from the Royal Veterinary College in 2015. After spending time in first opinion small animal practice, she returned to the RVC to start a PhD under the supervision of Professor Adrian Boswood and Professor Jonathan Elliott. She is researching pre clinical mitral valve disease in dogs.
Friday, June 15
2:45 PM – 3:00 PM
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