Spatial magnitudes of instantaneous QRS and ST-T vectors in Nigerians.

Spatial magnitudes of instantaneous QRS and ST-T vectors were studied in 664 (333 male: 331 female) normal Nigerians aged 15 to 90 (Mean: 39.1 +/- 16.7) years. Measurements were made manually using 8 divisions (octets) per QRS or ST-T waves. Not only the maximum amplitude but also several identical points on the QRS, J-point and St-T curves were higher in males than females. The R wave, J-point and ST-T vectors were oriented leftwards, inferiorly and posteriorly. The ST-segments were not iso-electric. The rates of ventricular depolarization (dV/dt) varied from one octet to another with maximum dV/dt occurring during the third octet. Ventricular repolarization was slower with peak rates during the fifth octet. It is concluded that this technique is simple, informative and practicable at bedside; but further studies are required to explore its diagnostic usefulness in patients with heart disease.