Ambulatory Arterial Stiffness Index Is Increased in Hypertensive
GIACOMO D. SIMONETTI, RODO O. VON VIGIER, ELKE WU¨HL, AND MARKUS G. MOHAUPT
Division of Paediatric Nephrology [G.D.S., R.O.V.], Department of Nephrology and Hypertension [G.D.S., M.G.M.], University of Bern,
3010 Berne, Switzerland; Division of Paediatric Nephrology [E.W.], University of Heidelberg, 69120 Heidelberg, Germany
ABSTRACT: Arterial hypertension in adults is often associated with
an increased arterial stiffness, which correlates with the ambulatory
arterial stiffness index (AASI) as derived from ambulatory blood
pressure (BP) measurements. The purpose of this study was to
demonstrate whether children with diagnosed hypertension have an
increased AASI as in hypertensive adults. AASI was calculated from
185 ambulatory BP measurements of 114 hypertensive and 71 nor-
motensive, healthy children. Hypertensive children had higher AASI
values compared with their normotensive healthy counterparts
(0.370 ? 0.120 versus 0.204 ? 0.199, p ? 0.0001). Children with
longer duration of hypertension or a history of primary or secondary
aortic coarctation displayed even more elevated AASI values. A
receiver operator curve derived cut-off of AASI set at 0.301 distin-
guished (p ? 0.0001) hypertensive from normotensive children with
an odds ratio of 8.2, a sensitivity of 81%, and a specificity of 65%.
Moreover, AASI correlated with pulse and systolic BP. In conclu-
sion, AASI is elevated in hypertensive children and correlates with
the duration and the origin of hypertension in childhood. (Pediatr
Res 64: 303–307, 2008)
the primary disease (i.e. chronic kidney disease, obesity), or
due to the effects of arterial hypertension on the cardiovascular
system by consecutively damaging target organs such as the
heart, the kidneys, and the brain (1). Increased left ventricular
cardiac mass is an established marker of cardiovascular target
organ involvement, but is only present in approximately 40%
of children with hypertensive diseases (2). Additional and
more sensitive noninvasive markers of hypertensive target
organ damage are required to determine outcomes and to
guide clinical and pharmacological management of childhood
hypertension (3). Arterial stiffness, which is a strong predictor
of cardiovascular complications and target organ damage in
both the general population and patients with hypertensive
diseases, would qualify as such a marker (4–7).
Most methods to measure arterial stiffness require special
and expensive equipment and trained observers, often not
available in clinical practice in a pediatric unit. A novel
method to address arterial stiffness based on 24-h ambulatory
iseases linked to arterial hypertension are associated with
a significant increased cardiovascular risk, either due to
blood pressure monitoring (ABPM) has been proposed (8): the
ambulatory arterial stiffness index (AASI), defined as one
minus the regression slope of diastolic over systolic blood
pressure (BP) measurements obtained during a 24-h period.
This ABPM-derived index has been shown to correlate with
classical measures of arterial stiffness, such as pulse wave
velocity (9), and to provide prognostic information on cardio-
vascular mortality and target organ damage throughout a wide
age range, including young individuals (10–12).
The purpose of this study was to demonstrate whether
AASI is increased in children with various hypertensive dis-
eases, as in hypertensive adults (9–11).
MATERIALS AND METHODS
Patients. ABPMs performed at the University Children’s Hospital of Berne
and of Heidelberg between January 2003 and November 2006 were retrospec-
tively reviewed. Children, aged 5–16 y, with hypertensive diseases were identi-
fied based on the formal diagnosis of arterial hypertension, as related to a given
child’s age, gender, and height (1,13), by elevated 24-h ABPM values and/or
antihypertensive treatment with a confirmed diagnosis of arterial hypertension.
ABPMs of healthy children served as control (14). Untreated children were
defined as being healthy in the absence of an acute or chronic illness and
presenting with weight, height, BMI, and 24-h ABPM measurements within the
5th – 95th percentile range. These healthy children were matched for age and
gender with their hypertensive counterparts. In addition, a group of young
hypertensive adults (WHO grade II-III) and a group of young healthy normoten-
sive adults, recruited at the Department of Nephrology and Hypertension, Uni-
versity Hospital of Bern, served as controls.
All subjects without clinical necessity for 24-h ABPM, who served as
controls, gave informed consent for ABPM as independently approved by the
ethical review board of the Universities of Heidelberg and of Bern, Switzer-
land, for adults and for children.
BP measurement. Ambulatory BP was recorded in all individuals on an
outpatient base using an oscillometric device (model 90207 Spacelabs Medical,
Issaquah, WA, or model bp one, Cardiette, Cavareno, Italy) that was set to take
a reading every 15–20 min during daytime and every 30–45 min during
nighttime. The two devices were compared with a noninvasive BP analyzer
(CuffLink, Dynatech, NV). The CuffLink includes options to perform a static
heart rates enabled comparisons of dynamic BP changes in both monitors. The
measured pressures were comparable and the resulting computed AASIs were
bp one of 0.249, model 90207 Spacelabs of 0.254. This indicates a difference in
the AASI between the two devices of up to a maximum of 2%.
Ambulatory arterial stiffness index. Using the individual 24-h BP read-
ings, diastolic was plotted against systolic BP and the linear regression slope
was calculated with appropriate statistical software. The slope was not forced
through the origin. AASI was defined as one minus the regression slope (8,9).
ABPM profiles were included for further analysis if a significant linear
Received December 13, 2007; accepted April 18, 2008.
Correspondence: Markus G. Mohaupt, M.D., Division of Hypertension, Department of
Nephrology and Hypertension, University of Bern, CH-3010 Berne, Switzerland; e-mail:
Supported by the Fondazione Ettore e Valeria Rossi (G.D.S.), the Swiss Renal
Foundation (G.D.S., M.G.M.), and the Swiss National Foundation (Nr. 3200B0–
Abbreviations: AASI, Ambulatory arterial stiffness index; ABPM, Ambu-
latory blood pressure monitoring; BP, Blood pressure; PP, Pulse pressure
Copyright © 2008 International Pediatric Research Foundation, Inc.
Vol. 64, No. 3, 2008
Printed in U.S.A.