CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 1, February 2012
AFRICA
39
severe anaemia groups (SE
=
3.7128;
p
=
0.006). For the ankle
systolic blood pressure, differences were significant in the mild
versus severe anaemia group (SE
=
5.7227;
p
=
0.002) and in the
moderate versus severe anaemia group (SE
=
4.3347;
p
=
0.001).
The mean pulse pressure for patients with mild anaemia was
significantly different from patients with moderate anaemia (SE
=
4.40621;
p
=
0.0013).
Discussion
The finding in this study of a significant reduction in ankle–
brachial index in sickle cell anaemia is intriguing. Ankle–
brachial index was found to be significantly lower in patients
with severe anaemia (haematocrit 18–20.9%) than in patients
with mild anaemia (haematocrit 30–35.9%). A comparison
of ankle–brachial index in patients and controls with compa-
rable haematocrit (30–35.9%) demonstrated no difference in
values. This suggests the significant role of chronic anaemia
in the reduction of ankle–brachial index in sickle cell anaemia,
although the mechanism of this effect is difficult to explain. It is
also possible that the subset of patients with severe anaemia may
have represented patients with more severe disease and therefore
more severe cardiovascular complications. Ankle–brachial index
in this study did not significantly correlate with the age of the
patients (duration of chronic anaemia) (Table 4) or with the
frequency of crisis.
Autopsy studies on sickle cell anaemia patients have reported
fibromuscular dysplastic narrowing involving multiple small
arteries, as well as intravascular plugs of sickled erythrocytes.
10
Focal fibromuscular dysplasia has been found at many differ-
ent sites in a variety of organs in non-sickling individuals.
11-13
Whether fibromuscular dysplastic narrowing of arteries may
contribute to reduction in ankle–brachial index in sickle cell
anaemia remains to be studied.
A reduced ankle–brachial blood pressure index has been asso-
ciated with significantly increased risk of cardiovascular disease
and stroke that is independent of other risk factors.
1,2
An earlier
study had documented reduced ankle–brachial index in sickle
cell patients who presented with leg ulcers.
14
Conclusion
A low ankle-to-brachial blood pressure ratio (
<
0.9) could be
a relatively easy-to-obtain marker of increased cardiovascular
risk in patients with sickle cell anaemia. Further studies are
recommended to evaluate the prognostic implications of reduced
ankle–brachial index in patients with sickle cell anaemia.
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TABLE 4. EFFECT OFAGE ONANKLE–BRACHIAL
INDEX IN PATIENTSAND CONTROLS
Age range (years)
Ankle–brachial index
t
-test
p
-value
Patients
Controls
18–22
0.945 (0.014)
1.041 (0.042) 2.081 0.052
23–27
0.933 (0.113)
1.041 (0.087) 3.859 0.001*
28–32
0.916 (0.116)
1.039 (0.037) 4.820 0.000*
33–44
0.859 (0.096)
1.014 (0.109) 3.088 0.015*
*Statistically significant.
