The association between diabetes and coronary artery disease (CAD) has been
recognized as a major public health problem in the developed world. While there
is an increased prevalence of silent myocardial ischaemia among asymptomatic
individuals with diabetes, diabetic individuals with CAD in their larger number are
usually asymptomatic, and when they present with signs of disease, there is
extensive and severe CAD. It should be noted that amongst black South African,
ischemic heart disease (IHD) remains rare, and there is little data linking diabetes
mellitus with IHD. However, contrary to early reports that have suggested a low
prevalence of CAD in black population in Africa, many studies have indicated a
rapid change on the spectrum of CAD in numerous parts of the African continent.
Despite the emerging report of high prevalence of risk factors there are only
limited data investigating prevalence of CAD in black African with diabetes.
The purpose of this thesis was to use myocardial perfusion imaging (MPI) at rest
and after stress testing to detect CAD in a group of asymptomatic black patients
suffering from diabetes and therefore assess the prevalence of CAD; to assess
the changes in myocardial perfusion in asymptomatic diabetic black individuals
and compare the differences seen in myocardial perfusion changes between the
asymptomatic diabetic black and, the asymptomatic diabetic white and Indian
individuals; to include data from symptomatic diabetic patients who were referred
for MPI as part of their routine clinical management for possible comparison
Consecutive 94 asymptomatic diabetic black patients and 50 asymptomatic
diabetic white and Indian patients were recruited from the outpatient diabetic
clinic of the Johannesburg hospital. Data from 90 subjects forming a group of
symptomatic diabetic patients, 45 blacks and 45 whites and Indians referred for
MPI as part of their clinical management were also analyzed. A two-day protocol
for SPECT MPI was used in all participants: on the first day the stress testing MPI while the rest MPI was consistently done on the second day. Both exercise
and pharmacologic stress testing were used. Technetium-99m methoxy-isobutylisonitrile
(MIBI) was used as the myocardial perfusion radiopharmaceutical.
Myocardial perfusion was assessed by means of semi-quantitative scoring
system to measure the extent and severity of perfusion abnormality. Visual
inspection of the reconstructed SPECT MPI images was carried out to assess
perfusion deficit where there was a doubt on the extent and severity of perfusion
abnormality. The QPS/QGS software allows obtaining resting and post stress left
ventricular ejection fraction (LVEF). The means and percentages on study
variables were obtained. The Spearmen correlation coefficient was used to
calculate correlations between variables. The Kruskal-Wallis test was used to
assess differences between black diabetic and white or Indian diabetic patients
and Wilcoxon scores (rank sum) two-sided were used to measure differences
within these racial groups.
There were 123 females (52.6%) and 111 males (47.4%) in total. From the
recruited participants, 53 (56.4%) asymptomatic females and 41 (43.6%)
asymptomatic males were blacks whereas 24 (48%) asymptomatic females and
26 (52%) asymptomatic males were whites or Indians. The symptomatic group
was comprised of 26 (57.8%) female and 19 (42.2%) male black patients and 20
(44.5%) female and 25 (55.5%) male white or Indian patients.
Asymptomatic diabetic black participants were younger than the participants from
the asymptomatic diabetic white and Indian group with a mean age of 60
(SD±7.2) years Vs 64 (SD±7.7) [p=0.003].
Fourteen percent of asymptomatic black participants had evidence of ischaemia
by showing improvement of perfusion on stress testing versus twenty eight
percent of white and Indian asymptomatic participants (p=0.62).
Perfusion defects that did not change from rest to post stress testing MPI (fixed
defects) were also noted in 20% of asymptomatic black and 26% of
asymptomatic white and Indian diabetic participants. These fixed perfusion defects are indicative of previous myocardial infarctions and therefore suggestive
of CAD.
No significant difference was noted on the changes of perfusion that could
account either for ischaemia or infract between asymptomatic diabetic black
participants and their white and Indian counterparts (p=0.47). The difference on
the improvement of perfusion from rest to post-stress MPIs or reversibility of
perfusion to suggest only the presence of ischaemia did not also show a
significant difference between these two racial groups (p=0.62).
Our data demonstrated a high prevalence of CAD in asymptomatic diabetic black
participants similar to other racial groups. Our study has demonstrated evidence
to recommend screening of asymptomatic diabetic black individuals in equal
manner than other races for the detection of CAD. More importantly, stress MPI
should be routinely used as a noninvasive investigation in our environment and
be utilized more actively in the management of all asymptomatic diabetic
patients
