CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 1, February 2012
AFRICA
37
An evaluation of ankle–brachial blood pressure index in
adult Nigerians with sickle cell anaemia
NI OGUANOBI, BJC ONWUBERE, OG IBEGBULAM, SO IKE, EC EJIM, O AGWU
Abstract
Aim:
There are few studies to be found in the literature
on ankle–brachial index in sickle cell disease. The aim of
this study was to compare ankle–brachial index of steady-
state adult sickle cell anaemia patients with that of normal
controls.
Methods:
A descriptive cross-sectional study of 62 sickle cell
anaemia patients and 62 age- and gender-matched normal
controls was carried out in the adult outpatient sickle cell
clinics and the cardiac centre of the University of Nigeria
Teaching Hospital (UNTH), Enugu, Nigeria from February
to August 2007. The supine brachial and ankle blood pres-
sures were measured separately with the cuff of the mercury
sphygmomanometer applied to the right arm and right calf,
respectively.
Results:
The ankle systolic blood pressure was lower in
patients with sickle cell anaemia than in the controls (
p
<
0.001). The mean indices for ankle–brachial index were 0.88
±
0.09 and 1.03
±
0.06, respectively for patients and controls.
This difference was statistically significant (
p
<
0.001).
Seventy three per cent of the patients had ankle–brachial
index less than 0.9 compared with controls (5%). This was
also significant (
p
<
0.001).
Keywords:
ankle–brachial blood pressure index, adult Nigerians,
sickle cell anaemia
Submitted 6/5/10, accepted 15/4/11
Cardiovasc J Afr
2012;
23
: 37–39
DOI: 10.5830/CVJA-2011-013
Ankle–brachial blood pressure index is defined as the ratio of
the brachial systolic blood pressure and the ankle systolic blood
pressure. A lower ankle–brachial index (
<
0.09) was associated
with a 4.2-fold increase in relative risk of cardiovascular mortal-
ity in a study on asymptomatic male subjects when compared
to those with a normal ankle–brachial index.
1
The Strong Heart
study showed that the adjusted hazard ratio for cardiovascular
mortality in the ankle–brachial index (
>
1.4) was 2.09 compared
to those with a normal ankle–brachial index.
2
An ankle–brachial blood pressure index greater than 1.3 indi-
cates poor compressibility of the arteries and signifies the pres-
ence of arterial calcification, which is common in diabetes melli-
tus. This makes the diagnosis of peripheral vascular disease less
reliable and is the main limitation of the ankle–brachial blood
pressure index. The other limitation of note is where patients
with a high-grade aorto–iliac stenosis or occlusion present with
a normal ankle–brachial blood pressure index at rest due to the
presence of a rich collateral network.
3
When compared to the gold standard of angiography, hospital
studies have shown an ankle–brachial blood pressure index less
than 0.9 to be 95% sensitive in detecting healthy subjects.
4
The
diagnostic criteria for peripheral artery disease based on ankle–
brachial blood pressure index described values of 0.9–1.3 as
normal, 0.7–0.9 as indicating mild disease, 0.41–0.69 as moder-
ate disease and
≤
0.4 as severe disease.
5
A Chinese population-based comparison of ankle–brachial
blood pressure index determined from consecutive auscultatory
or Doppler measurements at the posterior tibia and brachial
arteries showed that the mean ankle–brachial blood pressure
index values were significantly higher on Doppler than on
auscultatory measurements, with intermediate levels on oscil-
lometric determination. The differences between the three meas-
urements were not homogenously distributed across the range of
ankle–brachial blood pressure index values.
6
Few studies on this subject are to be found in the literature.
This study was aimed at comparing the ankle
–
brachial index of
steady-state adult sickle cell anaemia patients with that of normal
controls.
Methods
A descriptive cross-sectional study of 62 sickle cell anaemia
patients and 62 age- and gender-matched normal controls was
carried out in the adult outpatient sickle cell clinics and the
cardiac centre of the University of Nigeria Teaching Hospital
(UNTH), Enugu, Nigeria from February to August 2007. The
study subjects were drawn from adult patients (age
≥
18 years)
7
attending the adult sickle cell clinics of the UNTH, Enugu, who
had haemoglobin genotype SS on haemoglobin electrophoresis,
were in steady state and had consented to participate in the study.
Steady state is defined as absence of any crisis in the preceding
four weeks, and absence of any symptoms or signs attributable
to acute illness.
The weight and height of each subject were recorded and
the surface area was determined from a standard formula.
8
The
supine brachial and ankle blood pressures were measured sepa-
rately with the cuff of the mercury sphygmomanometer applied
to the right arm and right calf, respectively. The approximate
systolic blood pressures were obtained by palpation of the
brachial and the dorsalis pedis pulses. The cuff was deflated
and re-inflated to about 10 mmHg above the approximate
systolic value. Phase I and IV Korotkoff’s sounds were used
as systolic and diastolic blood pressure readings, respectively.
Department of Medicine, University of Nigeria Teaching
Hospital, Enugu, Nigeria
NI OGUANOBI, MBBS, FWACP,
BJC ONWUBERE, MBBS, Dip (Cardiol), FWACP, FMCP
SO IKE, MBBS, FMCP
EC EJIM, MBBS, FMCP
Department of Haematology, University of Nigeria Teaching
Hospital, Enugu, Nigeria
OG IBEGBULAM, MBBS, FWACP
O AGWU, MBBS
