Racial variations in electrocardiograms and vectorcardiograms between black and white children and their genesis.

Despite a general clinical impression that the ECG of black children differs from that of white children, none of the normal standards in children have taken race into consideration. Biographic data, blood pressure, hemoglobin, ECG, Frank VCG and echocardiogram were obtained in 244 normal children (124 blacks and 120 whites) aged 3-17 years and 144 measured parameters and 57 computed variables were analyzed. The children were divided into age groups of 3-5, 6-10, 11-14, and 15-17 years. The 15-17 year age group was small and therefore excluded. In the 3-5-year age group there were no sex differences (p greater than 0.05) nor were there any differences (p greater than 0.05) observed between black and white children. No significant sex differences were seen in 6-10-year-olds. However, the amplitude of the R wave in lead I, S in V1 and V4, and the sums of SV1 and RV6 as well as SV1 and RV5 on the ECG, and X to the left and Y to the inferior on VCG were greater in black than in white children (p less than 0.01). In 11-14-year-olds many sex-related differences were seen in each race. R in leads I, II, AVL, AVF and V4, S wave in V1 and V4R, and the sums of SV1 and RV5 as well as SV1 and RV6 in the ECG, and Y inferior and Z anterior in the VCG were higher (p less than 0.01) in black males than white males. However, no differences (p greater than 0.05) were observed between black and white 11-14-year-old girls. To understand the causes of these differences, comparisons of the biographic data, blood pressure, hemoglobins and echocardiograms were made. The height, weight, body surface area, chest circumference, AP diameter of the chest, and diastolic and systolic blood pressure were similar (p greater than 0.1) in all groups. The hemoglobin level was lower in black than white children (p less than 0.05). However, this difference was seen in all age-sex subgroups, suggesting that hemoglobin level was not responsible for the ECG-VCG differences. The LV posterior wall in diastole was thicker and the anterior chest wall to mid-LV distance was shorter in black than in white children in age-sex subgroups in which ECG-VCG differences were observed.(ABSTRACT TRUNCATED AT 400 WORDS)