The effects of breed, age, sex, and body weight on electrocardiographic parameters in military working dogs

Aim This study aimed to investigate the effects of breed, sex, age, and body weight on different electrocardiographic parameters in military working dogs (Labrador Retriever and German Shepherd). Materials and Methods Electrocardiographic recordings (paper speed = 25 mm/s and calibration = 10 mm/mV) were performed to obtain all the standard bipolar limb leads (leads I, II, and III) and unipolar augmented limb leads (leads aVR, aVL, and aVF). A total of 16 Labrador Retrievers and 14 German Shepherds were restrained manually in the right lateral recumbency without any tranquilizer or anesthetic drug. Amplitude and duration of P, QRS, and T wave, PR and QT interval, mean electrical axis, and heart rate were measured in each recording. Results There was no significant difference in electrocardiographic parameters across breed and sex. However, QRS duration tended to alter by breed (p<0.1) in Labrador Retrievers (0.04±0.005 s), which is lower than German Shepherds (0.05±0.005 s). PR interval was influenced by sex (p<0.1). PR interval was higher in females (0.13±0.005 s) than males (0.11±0.008 s). In addition, electrocardiographic values were not significantly affected by age and body weight, except that the amplitude of R wave was statistically affected by age (p<0.05). A correlation was found between the decrease in R wave amplitude and increase in age of dogs. Conclusion Different electrocardiographic parameters were within the normal range. A significant effect of age was seen on amplitude of R wave. However, the effect of breed, sex, and body weight was not significant on different electrocardiographic parameters in Labrador Retriever and German Shepherd dogs.