Effect of Body Habitus and Heart Rate on Accuracy of Aortic-Radial Transfer Functions for Predicting Central Hemodynamic Indices in Growing Children

Abstract

Central Systolic Blood Pressure (cSBP) and Central Augmentation Index (cAIx) have been independently associated with cardiovascular risk in adults, and can be estimated using a generalized peripheral-to-central transfer function. We hypothesize that transfer function accuracy and precision will be influenced by degree of growth and change in body habitus during periods of growth, such as in childhood. We studied the pulse pressure waveforms of 91 healthy children at 8-years of age, and subsequently at 14-years of age. Waveforms were obtained by high-fidelity applanation tonometry of the radial and carotid arteries. Individualized radial-to-carotid transfer functions were formulated at 8-years of age and applied at 14-years of age to estimate cSBP and cAIx. Accuracy was defined as the difference between directly measured and predicted values, and precision as the residuals. Changes in weight (vs. error: β = −0.22, p = 0.04; vs. residuals: β = 0.30; p < 0.01) and body mass index (vs. residuals: β = 0.28, p < 0.01), between 8 and 14 years of age were associated with accuracy and precision of individualized transfer functions in predicting cSBP at 14 years of age. Change in weight (vs. residuals: β = 0.30; p < 0.01) and heart rate (vs. residuals β = 0.32, p < 0.01) were associated with the precision in predicting cAIx. Changes in body habitus and heart rate over a 6-year period of growth are associated with the predictive accuracy and precision of individualized transfer functions in children suggestive of changes in the frequency response characteristics of an individual’s vascular system during growth periods.