The electrocardiogram of healthy rabbits in standard and chest leads and methods of recording it

Summary

Two hundred twenty-two electrocardiograms were recorded in 36 rabbits during a period of 20 months. Three standard and four chest leads were used.

Needle electrodes were introduced subcutaneously into the right, left anterior and left posterior extremity; the chest electrodes were introduced at the following points: points I (CR) and IV (CR₅) at the intersection of the vertical line (corresponding to the anterior axillary, line) with the horizontal line at the level of the heart; points II and III (CR₁ and CR₄) at the crossing of the parasternal lines with the horizontal. Electrocardiograms recorded with the animal on its back did not substantially differ from those recorded with the animal in the normal position. Five different positions of cardiac electrical axis were observed: normal, left, right, vertical and mixed. These may be spontaneously converted into borderline types. The number of cardiac contractions ranged from 180 to 330 per minute, averaging 250. The duration of the waves and intervals was between 0.01 and 0.02 seconds, depending on the number of cardiac contractions. The value of electric systole depended on the frequency of cardiac contractions. The ECG of the rabbit possesses specific features which should be taken into account in evaluating the cardiac function.