Changes in Central Aortic Pressure Levels, Wave Components and Determinants Associated with High Peripheral Blood Pressure States in Childhood: Analysis of Hypertensive Phenotype

Abstract

The aims were to determine whether children's high peripheral blood pressure states (HBP) are associated with increased central aortic blood pressure (BP) and to characterize hemodynamic and vascular changes associated with HBP in terms of changes in cardiac output (stroke volume, SV), arterial stiffness (aortic pulse wave velocity, PWV), peripheral vascular resistances (PVR) and net and relative contributions of reflected waves to the aortic pulse amplitude. We included 154 subjects (mean age 11; range 4-16 years) assigned to one of two groups: normal peripheral BP (NBP, n = 101), defined as systolic and diastolic BP < 90th percentile, or high BP (HBP, n = 53), defined as average systolic and/or diastolic BP levels ≥90th percentile (curves for sex, age and body height). The HBP group included children with hypertensive and pre-hypertensive BP levels. After a first analysis, groups were compared excluding obese and dyslipidemic children. Peripheral and central aortic BP, PWV and pulse wave-derived parameters (augmentation index, forward and backward wave components' amplitude) were measured using gold-standard techniques, applanation tonometry (SphygmoCor) and oscillometry (Mobil-O-Graph). Independent of the presence of dyslipidemia and/or obesity, aortic systolic and pulse BP were higher in HBP than in NBP children. The increase in central BP could not be explained by an increase in the relative contribution of reflections to the aortic pressure wave, higher PVR or by an augmented peripheral reflection coefficient. Instead, the rise in central BP would be explained by an increase in the amplitude of both incident and reflected wave components.

Haemodynamics of Hypertension in Children

“…The ENIGMA study [ 16 ••] reported AIx to be significantly lower in young adults with ISH, compared to control group. Other studies [ 25 ••, 32 , 51 ••] have reported no significant difference in AIx between hypertensive and control children and adolescents. A more direct measure of reflection is the reflection coefficient, obtained by mathematical separation of forward and backward waves (from pressure and flow), as the ratio of the amplitude of the backward to forward wave.…”

Reference Intervals of Central Aortic Blood Pressure and Augmentation Index Assessed with an Oscillometric Device in Healthy Children, Adolescents, and Young Adults from Argentina

“…Otherwise, AS and arrival time and amplitude of wave reflections are the main determinants of cSBP and cPP, while peripheral vascular resistances and cardiac output are the main determinants of MBP and cDBP. In this context, it is important to emphasize that simultaneous measurements of central (aortic) BP and cAIx (using a single device) in children and adolescents allow us not only to know if cSBP and cPP are within physiological levels, but also in case of abnormal values to realize if they were associated or not with increased wave reflection levels (cAIx) [ 31 , 32 ].…”

Aplicabilidade dos marcadores de rigidez arterial na doença arterial periférica

“…12 Therefore, pulse pressure (PP), which the difference between SysP and DiaP, increases in the peripheral arteries; for example, between the root of the aorta and the brachial artery, PP is amplified by around 14 mmHg. [12][13][14] This is a physiological finding known as PP amplification ( Figure 2).…”

“…This phenomenon is known as pulse pressure amplification and is calculated by dividing systolic pressure central (SysPc) by peripheral systolic pressure (SysPp). Adapted from García-Espinosa et al 14 occur in any segment in which there is discontinuity of flow, such as at bifurcations and, primarily, when the incident waves reach the peripheral arteries with greater resistance and lower elasticity. Thus, to aid understanding, the waves can be designated as the incident wave (or ejection wave) and the reflected wave and the resulting pulse wave is the sum of the incident wave and the reflected wave ( Figure 3).…”

“…Thus, to aid understanding, the waves can be designated as the incident wave (or ejection wave) and the reflected wave and the resulting pulse wave is the sum of the incident wave and the reflected wave ( Figure 3). 14 Figure 4 illustrates the pulse wave at the root of the aorta in a scenario of increased arterial stiffness, whether due to aging or atherosclerosis. As a result of the elevated PWV, the reflected wave arrives at the proximal aorta prematurely, at the start of systole (point P1 on the graph).…”