Acute postural change--a novel approach to blood pressure tracking in children

Among 1443 children, aged 5 to 18, followed for five consecutive years, we identified 68 who tracked consistently in the lowest blood pressure (BP) quartile and 114 in the highest. BP and corresponding heart rate were taken with subjects in the supine, sitting and erect postures. BP quartiles were established for each height category. Children consistently in the highest BP quartile had greater relative weight and higher heart rates in all three positions. On assuming the erect posture, children in the lowest BP quartile showed an increase in systolic BP, while those in the highest BP quartile showed a decrease. Both groups showed an increase in diastolic BP. On assuming the erect posture, subjects in the two groups showed no difference in heart rate change; subjects in the highest BP quartile did not show the additional reflex increase in heart rate to be expected in response to the decrease in systolic blood pressure. This combination of BP and heart rate findings suggests a subtle change in the baroreceptor reflex.