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Vertebral Left Atrial Size in Dogs with Preclinical Myxomatous Mitral Valve Disease

Amara Estrada, DVM, DACVIM (Cardiology), University of Florida


|August 2022

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In the literature

Lee D, Yun T, Koo Y, et al. Change of vertebral left atrial size in dogs with preclinical myxomatous mitral valve disease prior to the onset of congestive heart failure. J Vet Cardiol. 2022;42:23-33. doi:10.1016/j.jvc.2022.05.003


Vertebral left atrial size (VLAS) is a radiographic measurement that objectively estimates left atrial size and can help determine whether cardiac enlargement is present in dogs with suspected or diagnosed myxomatous mitral valve disease (MMVD). VLAS can be useful when other imaging modalities (eg, echocardiography, thoracic-focused point-of-care ultrasonography) cannot be performed (eg, due to financial constraints, lack of availability, lack of technical expertise). Increase in vertebral heart size (VHS) prior to onset of congestive heart failure (CHF) and rate of change in VHS over time (VHS/month) can help predict possible occurrence of CHF.1-3 Additional studies in dogs with MMVD have reported VLAS ranges for each stage of disease.4-6

This retrospective study investigated whether VLAS can help determine if dogs with preclinical MMVD are at higher or lower risk for developing CHF. Dogs (n = 41) were assigned to 2 groups based on whether or not CHF developed within 180 days of initial diagnosis of MMVD. Radiographic and echocardiographic parameters, including VLAS and rate of change in VLAS over time (VLAS/month), at 3 time points (ie, first visit, 1-180 days postdiagnosis, 181-360 days postdiagnosis) were compared between groups. Results demonstrated no significant difference in VLAS between the groups at the first visit; however, VLAS and change in VLAS over time were significantly higher in the group that developed CHF within 180 days of initial diagnosis of MMVD.


Key pearls to put into practice:


Not all patients in the current retrospective study received pimobendan; results should thus be interpreted with caution. Pimobendan is administered to most dogs with stage B2 MMVD based on the ACVIM consensus statement and EPIC clinical trial results.7,8 A follow-up study of this cohort of dogs found that VHS consistently decreased during the first several months of treatment; this decrease was associated with a better outcome, longer preclinical time period, and reduced risk for developing CHF within 6 months.


Owners of dogs with MMVD should be instructed on home resting respiratory rate monitoring. Effective monitoring and accurate measurement of resting respiratory rate at home is an effective way to monitor patients between visits to the clinic. Small changes can be communicated to clinicians, allowing phone consultations and possible initiation of a furosemide trial to help avoid emergency clinic visits during an episode of CHF.


A cut-off VLAS value of >2.95 was specific for identifying dogs with impending (ie, within 180 days) CHF, but sensitivity was low, indicating that a large number of dogs with VLAS >2.95 will not develop CHF within 6 months; however, this measurement can help identify dogs at greater risk.


For global readers, a calculator to convert laboratory values, dosages, and other measurements to SI units can be found here.

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