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The T wave is a poorly characterized electrocardiographic variable in small animals. Therefore, this study aimed to describe T wave features in a large population of healthy dogs. Medical records were reviewed to identify healthy dogs ≥one-year-olds that underwent an electrocardiogram. T wave qualitative (morphology, polarity, and concordance between R and T waves) and quantitative (duration, amplitude, mean electrical axis, ratio between T and R waves amplitudes, interval from the peak to the end of the T wave, and ratio between the duration of the latter interval and that of the QT) variables were evaluated. Continuous and categorical variables were compared between dogs of distinct sex, body weight (BW), age and somatotype using the Mann–Whitney U test and χ2 test, respectively. Spearman's correlation coefficients between quantitative variables and age and BW were calculated. Reference intervals of quantitative variables were determined in the overall population. One hundred and twenty-nine dogs were enrolled. Concerning morphology, the asymmetrical (slow/fast) pattern occurred more frequently than the symmetrical and biphasic ones. Concerning polarity, positive T waves occurred more frequently than negative and neutral ones. T and R waves were predominantly concordant. No meaningful differences were found when comparing qualitative and quantitative variables between dogs of distinct sex, BW, age and somatotype. No significant correlations were found between quantitative variables and age and BW. Reference intervals of quantitative variables are provided. Canine T wave features were addressed and statistically reliable reference intervals made available for clinical use. [ABSTRACT FROM AUTHOR]

Whether a brachymorphic conformation may lead to electrocardiographic peculiarities diverging from generic reference intervals (RIs) cited in textbooks remains to be established. Therefore, this study aimed at evaluating electrocardiographic variables in one of the most common brachymorphic breed, namely the French Bulldog (FB). Medical records were retrospectively reviewed to identify healthy FBs ≥1-year-old that underwent an electrocardiogram. The Mann–Whitney U test or the Student's t-test was used to compare continuous variables among male and female dogs, while the χ2 test was used for categorical variables. Spearman's correlation coefficients between electrocardiographic measurements and age and body weight were also calculated. Moreover, electrocardiographic RIs were determined. Eighty healthy FBs were enrolled; their electrocardiographic variables fitted with generic RIs, with the exception of the QRS-complex mean electrical axis (QRS-MEA). The median QRS-MEA value was 43.5° (from −18° to +90°). A QRS-MEA shift was found in 24/80 (30%) dogs; in all cases, it was a left shift (median 26°, from −18° to +39°). Specifically, 20 dogs showed a slight left shift (from +39° to +14°), while four dogs showed a marked one (from +9° to −18°). No meaningful differences were found when comparing electrocardiographic variables between males and females. No significant correlations between electrocardiographic variables and age or body weight were found, with the exceptions of the P-wave amplitude, PQ-interval duration and QT-interval duration. Healthy FBs can present a left shift of QRS-MEA. These data should be considered when interpreting FBs' electrocardiograms. [ABSTRACT FROM AUTHOR]