[The voltage of R-waves in the normal electrocardiogram of the conscious beagle]

Mean values for body weight of 12.5 kg, heart weight of 103 g, heart rate of 109 actions/min and from ECG lead II an R-wave amplitude (voltage) of 1.6 mV (0.5-2.7 mV) were calculated in 118 healthy untreated beagle dogs (58 males, 60 females). The values of these parameters are somewhat higher in the males than in the females. The body postures of the dogs (standing, sitting, lying) during the recording of the ECGs scarcely influence the amplitude of RII but do distinctly alter those of R1 and RIII corresponding to the related changes in the direction of the electrical heart axis. Body and heart weights are positively correlated (r = +0.74) within the whole sample. There are, however, no correlations between heart weight and rate, heart rate and RII-amplitude nor between amplitude RII and heart weight within the range of the physiological values investigated making use of interindividual consideration. In 35 beagle dogs the smallest voltage changes were found in RII after recordings in series compared intraindividually. However, significant variations in RI and RIII were apparent. Furthermore normal ECGs with low voltage of RII or QRSII were revealed as mostly secondary low voltages due to sagittal type by our special lead "DV-L" (dorsoventral left). ECGs with high voltage of RII, which showed a lower mean amplitude in DV-L, served as control test. The results are commented on in detail. Possible relationships between heart weight, volume of ventricles, and heart rate on the one hand and the voltage of R or QRS on the other hand are discussed.