The canine T wave: a retrospective analysis on qualitative and quantitative T wave variables obtained in 129 healthy dogs and proposed reference intervals.

INTRODUCTION/OBJECTIVE: 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. ANIMALS, MATERIALS, AND METHODS: 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. RESULTS: 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. CONCLUSIONS: Canine T wave features were addressed and statistically reliable reference intervals made available for clinical use.

Retrospective evaluation of the ST segment electrocardiographic features in 180 healthy dogs.

OBJECTIVES: Normal features of the ST segment are poorly characterised in dogs. This study aimed to describe ST segment characteristics in a population of healthy dogs. MATERIALS AND METHODS: Medical records were reviewed to identify healthy dogs that underwent an electrocardiogram. Several ST segment qualitative parameters were evaluated: presence/absence of deviation, type of deviation (depression/elevation) and morphological patterns of depression (horizontal, downsloping, upsloping and sagging) and elevation (horizontal, concave and convex). Moreover, the amplitude of ST segment depression/elevation was measured. The potential effect of sex, bodyweight, age and somatotype on the presence/absence of ST segment deviation was evaluated through binary logistic regression. RESULTS: One hundred and eighty dogs were enrolled. The deviation was evident in 43 of 180 dogs (23.9%), among which 36 showed depression and seven showed elevation. The median depression amplitude was 0.1 (range 0.05 to 0.3) mV. The mean elevation amplitude was 0.136 ±0.055 mV. Concerning depression morphology, the horizontal pattern was overrepresented, followed by the downsloping and upsloping ones. Concerning elevation morphology, all dogs showed a concave pattern. No meaningful effect of sex, bodyweight, age and somatotype on the presence/absence of ST segment deviation was documented. CLINICAL SIGNIFICANCE: Normal features of canine ST segment were described and made available for clinical use.

Assessment of Left Atrial Deformation and Function by 2-Dimensional Speckle Tracking Echocardiography in Healthy Dogs and Dogs With Myxomatous Mitral Valve Disease.

BACKGROUND: The assessment of left atrial (LA) function by 2-dimensional speckle tracking echocardiography (STE) holds important clinical implications in human medicine. Few similar data are available in dogs. OBJECTIVES: To assess LA function by STE in dogs with and without myxomatous mitral valve disease (MMVD), analyzing LA areas, systolic function, and strain. ANIMALS: One hundred and fifty dogs were divided according to the American College of Veterinary Internal Medicine classification of heart failure: 23 dogs in class A, 52 in class B1, 36 in class B2, and 39 in class C + D. METHODS: Prospective observational study. Conventional morphologic and Doppler variables, LA areas, and STE-based LA strain analysis were performed in all dogs and results were compared among groups. Correlation analysis was carried out between LA STE variables and other echocardiographic variables. RESULTS: Variability study showed good reproducibility for all the tested variables (coefficient of variation <16%). Left atrial areas, fractional area change, peak atrial longitudinal strain (PALS), peak atrial contraction strain, and contraction strain index (CSI) differed significantly between groups B2 and C + D and all the other groups (overall P < .001), whereas only PALS differed between groups B1 and A (P = .01). Left atrial areas increased with progression of the disease, whereas LA functional parameters decreased. Only CSI increased nonsignificantly from group A to group B1 and then progressively decreased. Thirty-one significant correlations (P < .001, r > .3) were found between conventional left heart echocardiographic variables and LA areas and strain variables. CONCLUSIONS AND CLINICAL IMPORTANCE: Left atrial STE analysis provides useful information on atrial function in the dog, highlighting a progressive decline in atrial function with worsening of MMVD.