CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 1, January/February 2014
4
AFRICA
Cardiovascular Topics
Vascular calcification is not associated with increased
ambulatory central aortic systolic pressure in prevalent
dialysis patients
Robert J Freercks, Charles R Swanepoel, Kristy L Turest-Swartz, Henri RO Carrara, Sulaiman EI Moosa,
Anthony S Lachman, Brian L Rayner
Abstract
Introduction:
Central aortic systolic pressure (CASP)
strongly predicts cardiovascular outcomes. We undertook to
measure ambulatory CASP in 74 prevalent dialysis patients
using the BPro (HealthStats, Singapore) device. We also
determined whether coronary or abdominal aortic calcifica-
tion was associated with changes in CASP and whether inter-
dialytic CASP predicted ambulatory measurement.
Methods:
All patients underwent computed tomography for
coronary calcium score, lateral abdominal radiography for
aortic calcium score, echocardiography for left ventricular
mass index and ambulatory blood pressure measurement
using BPro calibrated to brachial blood pressure. HealthStats
was able to convert standard BPro SOFT
®
data into ambula-
tory CASP.
Results:
Ambulatory CASP was not different in those with-
out and with coronary (137.6 vs 141.8 mmHg, respectively,
p
=
0.6) or aortic (136.6 vs 145.6 mmHg, respectively,
p
=
0.2)
calcification. Furthermore, when expressed as a percentage
of brachial systolic blood pressure to control for periph-
eral blood pressure, any difference in CASP was abolished:
CASP: brachial systolic blood pressure ratio
=
0.9 across all
categories regardless of the presence of coronary or aortic
calcification (
p
=
0.2 and 0.4, respectively). Supporting this
finding, left ventricular mass index was also not different in
those with or without vascular calcification (
p
=
0.7 and 0.8
for coronary and aortic calcification). Inter-dialytic office
blood pressure and CASP correlated excellently with ambula-
tory measurements (
r
=
0.9 for both).
Conclusion:
Vascular calcification was not associated with
changes in ambulatory central aortic systolic pressure in
this cohort of prevalent dialysis patients. Inter-dialytic blood
pressure and CASP correlated very well with ambulatory
measurement.
Keywords:
vascular calcification, central blood pressure, dialy-
sis, ambulatory blood pressure monitoring
Submitted 4/4/13, accepted 14/11/13
Cardiovasc J Afr
2014;
25
: 4–8
DOI: 10.5830/CVJA-2013-081
Vascular calcification (VC) is a novel vascular risk factor strongly
associated with mortality in dialysis patients.
1,2
Although various
explanations exist for this association, one mechanism is through
alterations in pulse-wave velocity (PWV). Vascular calcification
is associated with increased aortic PWV,
3
which in turn is
associated with raised central aortic systolic pressure (CASP)
and reduced coronary perfusion.
4,5
As a result, brachial pressure
may significantly under- or over-estimate central pressure.
6
Not surprisingly therefore, central blood pressure parameters
have been shown to predict hard cardiovascular endpoints
(including mortality) better than concomitant brachial
measurements.
7-10
Whether vascular calcification is directly
linked to central pressures is, however, unknown since there are
many determinants of aortic stiffening other than calcification.
Furthermore, a primarily damaged and stiff aorta may be the
target for secondary deposition of calcium.
11
CASP can be calculated using applanation tonometry-derived
peripheral pulse waveforms and associated software.
12
This
avoids the obvious disadvantages of invasive central pressure
determination. The major disadvantage of standard techniques,
however, is the one-dimensional static measurement that is
obtained, with no information on ambulatory values or nocturnal
dipping status.
Loss of normal nocturnal systolic blood pressure dipping is
prevalent in chronic kidney disease (CKD) and likely contributes
Renal Unit, Groote Schuur Hospital, University of Cape
Town, South Africa
Robert J Freercks, FCP (SA), Cert Neph, MPhil (UCT),
Charles R Swanepoel, FRCP (Edin)
Kristy L Turest-Swartz, MPH (UCT)
Brian L Rayner, FCP, MMed
School of Public Health and Family Medicine, University of
Cape Town, South Africa
Henri RO Carrara, MPH (UMEA)
Radiologist, 2-Military Hospital, Cape Town
Sulaiman EI Moosa, MPhil, BSc (Hon), FCRad (Diag)
Cardiologist, 2-Military Hospital, Cape Town
Anthony S Lachman, FCP (SA), FACC, FACP
