Electrocardiographic axis deviation in Navajo and Apache indians.

It has been our clinical impression that the range of the mean frontal-plane electrocardiographic QRS axis was greater than might have been anticipated in healthy Navajo and Apache Indians. To determine whether this clinical impression was correct, electrocardiograms were obtained from 146 Navajo, 144 Apache, and 159 non-Navajo non-Apache schoolchildren with normal findings on cardiovascular examinations. A mean frontal-plane QRS axis between -1 degrees and -90 degrees was present in 19 percent of the Navajo, 12 percent of the Apache, and 2 percent of the control schoolchildren. A mean frontal-plane QRS axis between +91 degrees and +180 degrees was present in 18 percent of the Navajo, 19 percent of the Apache, and 5 percent of the control schoolchildren. There is a high incidence of electrocardiographic mean frontal-plane QRS axis deviation in healthy Navajo and Apache schoolchildren.