Electrical axis of the heart in healthy adult Nigerians.

The twelve-lead electrocardiogram (ECG) was analysed to describe the frontal plane P wave, T wave and QRS axes in 1220 healthy adult Nigerians. Axis determination was based on the principle of resolution of forces along the three Einthoven and three Goldberger leads referred to as the 'hexaxial reference system'. The P-wave axis ranged from 37.8 to 72.6 degrees without sex variation but with slight rightward shift with age. The T-wave axis ranged from 24.1 to 68.5 degrees without exhibiting age or sex variation. The proposed ranges of QRS axis deviation in the Nigerian were 0 to +90 degrees for normal, 0 to -90 degrees for LAD, and +90 to +/- 180 degrees for RAD. There was no sex variation in QRS axis until after the sixth decade of life. The axis in Nigerians was more leftward than that of Caucasians of the same age; but in both races the QRS axis exhibited a leftward shift with age.