Retrospective evaluation of notched and fragmented QRS complex in dogs with naturally occurring myxomatous mitral valve disease

Abstract

Background: 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.Objective: 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. Methods: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 posthoc test was used to assess the differences in continuous data between control and MMVD groups.Results: 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=0.75) nor did the number of leads with a nQRS correlate with left atrial size (r=-0.48; p=0.5). The number of dogs with fQRS did not differ among classes of MMVD (p=0.21). nQRS and fQRS were more prevalent in dogs with MMVD compared to control dogs (p<0.01).Conclusions: 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.

Case report: Long-term survival in puppies assessed with echocardiography, electrocardiography and cardiac troponin I after acute death in littermates due to parvoviral myocarditis

“…But while multiple studies have demonstrated that S-T segment elevation can be a sign of myocardial ischemia, S-T segment elevation as an indicator of cardiac damage specifically from PMC is an occasional but inconsistent finding (18). Conduction abnormalities, as seen with notched QRS complexes have been reported in a variety of cardiac diseases in human and canines, but again are occasionally but not consistently seen in puppies who later succumb to PMC (18, [28][29][30].…”