Electrocardiograms (ECGs) were recorded from 81 clinically healthy beagle dogs of both sexes, 10 to 11 months old, by apex-base bipolar lead in order to obtain background data for a general toxicity study. The result obtained are as follows :
1. Respiratory sinus arrhythmia, which seemed to be a usual rhythm pattern, was observed in almost all the dogs, a few of which were affected with sinus tachycardia. It was probably induced by the difference in sensitivity among dogs to the circumstance of recording.
2. The standard figure of ECG consisted of positive P-wave, Rs type of QRS-complex, and positive T-wave. Biphasic T-waves, however, as well as some types of variation in the QRS-complex, were observed in a few dogs. In almost all the dogs ST-segments slightly deviated from the baseline. It was not determined whether these variations from the standard figure of ECG were normal or not in the present study.
3. No differences were seen in the conduction time and the amplitude of P, R, and T-waves in each deflection between the results of the present study and those reported by previous researchers. There seemed to be a carretation between the difference in the amplitude of the S-wave and that in the strain of beagle dogs.
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