Comparative studies on the wide frequency band electrocardiogram and vectorcardiogram in pigeon and mouse

Wide frequency band ECG and vectorcardiogram in anesthetized pigeon and mouse were studied from the standpoint of comparison. The key results were as follows: in pigeon, the direction of the main QRS was inverted in leads II, III and aVF, and upright in lead aVR, which was contrary to that in mouse. The T wave was upright in leads II, III and aVF, but inverted in lead aVR in pigeon, which was the same as that in mouse. In pigeon, there was a large notch on the upstroke of the S wave in lead II without exception, but there was no such notch in the corresponding lead in mouse. The QRS vector loop in the frontal plane lay between -90 and -180 degrees in pigeon, while that of mouse lay between 0 and 90 degrees. The relative power of high frequency range (80-1000 Hz) of the QRS in lead II was approximately 15% in pigeon, but 55% in mouse. The direction of the main QRS was contrary in pigeon and mouse because the subepicardial muscles were depolarized before the subendocardial muscles in pigeon, but the latter were depolarized before the former in mouse. The direction of the T waves was the same in both pigeon and mouse because subepicardial muscles were all repolarized before subendocardial muscles.