Correlation between the surface electrocardiogram and air sac morphology in the White Leghorn rooster

¹ Department of Zoology, Cornell University, Ithaca, New York

The morphology of the bird offers a new approach to consideration of the effects of insulation of the heart on the conduction of cardiac potentials to the body surface. The avian heart is insulated cranially and dorsolaterally by large air spaces, which introduce marked inhomogeneities in the volume conductor. Surface electrocardiograms of male White Leghorns were obtained using multiple leads encircling the torso at the levels of the interclavicular joints, ventricle and xiphoid. Magnitude, appearance and duration of the electrocardiographic complexes of 300 leads for each of 15 birds were analyzed. Vectors were plotted for sagittal, horizontal and frontal planes. Low voltage deflections occurred in 46% of the interclavicular leads, 20% of ventricular leads and none of the xiphoid leads. This deflection pattern is due in part to the insulating effect of air sacs between the heart and body surface.