The normal electrocardiogram of the conscious beagle dog

Abstract

The relationships between sex, age, and bodyweight of animals and the parameters heart rate and durations of PQ-interval, QRS-complex, and QT-interval (leads I, II, III) were investigated in 432 male and female beagle dogs (Chbb: Beagle strain; age, 187–646 days; weight, 5.8–18.5 kg). The dogs, kept under standard conditions, were considered clinically healthy at the time of recording and were not treated with drugs or conditioned. The statistical methods applied consisted of: analyses of linear correlation, polynomial regression, and linear covariance. No dependence of heart rate and ECG parameters on sex, age, or weight was evident. The following ranges were observed: heart rate, 45–220 beats/min (mean, 112 beats/min); PQ-interval, 0.080–0.160 sec (mean, 0.107 sec); QRS-complex, 0.030–0.060 sec (mean, 0.042 sec); QT-interval, 0.140–0.240 sec (mean, 0.188 sec). The frequency distributions for heart rate and the ECG parameters were almost symmetrical. A negative correlation between heart rate and QT-interval was shown to be statistically significant and biologically useful. Upper and lower tolerance limits for the regression line for a given heart rate and the dependent QT-interval were determined. Furthermore, tolerance values were calculated for all mentioned ECG parameters including 95% of the population. A slight negative correlation also existed between heart rate and PQ-interval. No further correlations could be detected. Heart vectors (using the leads I, II, III, and aVR, aVL, aVF) were determined in 44 other beagles by means of a hexaaxial system. The values were between +30 and +90 with a mean of 58.3°. Physiological ECG variations can be observed in healthy untreated beagle dogs.