Background: In adults, central systolic blood pressure (cSBP) and augmentation index (cAIx) are independently associated with cardiovascular (CV) events and mortality. As CV disease begins in early life, there is increasing interest in central hemodynamic indices in children. We aimed to assess the accuracy of current techniques against invasive intra-aortic measurements in children.
Methods: Intra-aortic pressure waveforms were recorded with simultaneous brachial, radial and carotid waveforms in 29 children (6.7±3.9 years old) undergoing cardiac catheterization. Non-invasive blood pressure (BP) was recorded by brachial cuff oscillometry. Adult and age-appropriate transfer functions (TF) (brachial adult: b-aTF; radial adult: r-aTF; radial for 8 year-old children: TF8; and radial for 14 year-old children: TF14) were used to synthesize central aortic waveforms from peripheral waveforms calibrated either to invasively or non-invasively recorded BP. Central hemodynamic indices were measured by pulse wave analysis.
Results: cSBP measured from invasively calibrated r-aTF (β=0.84; ICC=0.91; mean error±SDD=-1.0±5.0 mmHg), TF8 (β=0.78; ICC=0.84; mean error±SDD=4.4±5.6 mmHg), and TF14 (β=0.82; ICC=0.90; mean error±SDD=2.0±4.7 mmHg) -synthesized central waveforms correlated with and accurately estimated intra-aortic cSBP measurements, while non-invasively calibrated waveforms did not. cAIx derived from TF-synthesized central waveforms did not correlate with intra-aortic cAIx values. The degree of error in cAIx estimation was TF-dependent.
Conclusions: The currently available r-aTF accurately estimates cSBP only with invasive pulse pressure calibration. Age-appropriate TFs do not appear to provide additional benefit in the estimation of cSBP. Accuracy of cAIx estimation appears to be TF dependent, suggesting that age-appropriate TFs may be beneficial for cAIx estimation in children.