Parasympathetic Modulation is Correlated With Baroreflex Sensitivity and Orthostatic Pressor Response in Childhood.

Background: The objective of our case-control study was to evaluate the determinants of childhood cardio-vagal baroreflex failure and exaggerated orthostatic pressor response, which are risk factors for subsequent hypertension.

Methods: Four groups of children were matched for sex and age: 12 with congenital central hypoventilation syndrome (autonomic nervous system dysfunction), 12 with chronic kidney disease (frequently abnormal blood pressure [BP]), 12 with sickle cell disease (frequently abnormal orthostatic BP), and 24 control children (preterm birth with normal BP). The children underwent tonometry evaluation (aortic systolic BP) and continuous BP and ECG measurements in supine and standing positions, allowing ambulatory BP monitoring and the computation of heart rate variability indices, baroreflex sensitivity (BRS), and orthostatic systolic BP response.

Results: Supine and standing BRS correlated significantly with aortic systolic BP (ρ = -0.34, ρ = -0.52, respectively), daytime systolic BP (ρ = -0.33, ρ = -0.54, respectively), low frequencies power in similar body positions (supine: ρ = 0.68, standing: ρ = 0.65), and high frequencies (HF) power (ρ = 0.78, ρ = 0.76, respectively). Orthostatic BP response correlated significantly with standing BRS (ρ = -0.38) and standing HFnu (ρ = -0.46). In multivariate analyses, only supine and standing HF power remained independently associated with the respective BRS, while standing HFnu and standing BRS were independently associated with the orthostatic pressor response.

Conclusions: Defective parasympathetic modulation's detrimental effect on baroreflex sensitivity and the orthostatic pressor response in childhood is evident, regardless of the underlying pathology.