Comparison of Spatial QRS-T Angle in Different Healthy Racial Groups

The spatial QRS-T angle has been found to be an important prognostic predictor for cardiovascular mortality. The aim of this study was to compare the normal limits of the spatial QRS-T angle in four cohorts of apparently healthy, different racial groups. The University of Glasgow ECG Analysis Program was used to analyze the ECGs. The orthogonal X, Y and Z lead data was derived from the standard lead data, using the inverse Dower method, and the spatial QRS-T angle was calculated. Statistical analysis was undertaken using the SPSS Statistics package. Angles were calculated for 2553 males and 1649 females aged between 18 and 87 years. The mean spatial QRS-T angle for males in Black, Caucasian, Chinese and Indian populations was 67 +/- 27 degrees, 69 +/- 29 degrees, 59 +/- 26 degrees and 71 +/- 33 degrees respectively with the values for the Chinese cohort being significantly different than the other cohorts ( P<0.001). For females, the corresponding mean values were 42 +/- 23 degrees, 57 +/- 25 degrees, 40 +/- 22 degrees and 41 +/- 25 degrees, with the values for the Caucasian cohort being significantly different from the others ( P<0.001). In all ethnic groups, the mean spatial QRS-T angle was higher in males than in females (overall mean difference of 21 degrees). There was a wide range of upper limits of normal for the racial groups. Race and gender should be considered when assessing the spatial QRS-T angle.