Abstract:
Myxomatous mitral valve disease (MMVD) is the most common cardiac disease in dogs. The
association of QRS notching (nQRS) or fragmentation (fQRS) with disease severity is currently
unknown. The study objective was to assess the prevalence of nQRS and fQRS in dogs with
MMVD and its severity according to ACVIM classification and to compare the results with a
group of healthy dogs. This retrospective cross-sectional study included 34 healthy control
dogs and 155 dogs with spontaneous MMVD (42% of dogs in class B1, 23% in class B2 and
35% in class C). fQRS was defined as nQRS complexes in two contiguous leads in the frontal
plane (leads I and aVL) and (II, III or aVF). A one-way ANOVA with Bonferroni post-hoc test
was used to assess the differences in continuous data between control and MMVD groups.
Of the MMVD group, 58% showed nQRS in at least one lead and 27% presented fQRS. There
was no difference between the number of leads with a nQRS and disease severity (p ¼ 0.75)
nor did the number of leads with a nQRS correlate with left atrial size (r ¼ 0.48; p ¼ 0.5). The
number of dogs with fQRS did not differ among classes of MMVD (p ¼ 0.21). nQRS and fQRS
were more prevalent in dogs with MMVD compared to control dogs (p < 0.01). This study
did not identify any relationship between the number of leads with a nQRS and disease
severity. However, dogs with MMVD had a higher prevalence of nQRS and fQRS compared
to control group.
