CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 2, March/April 2011
86
AFRICA
Methods
Ninety-six patients (36 women, 60 men, mean age 57
±
8.5
years) were included in the study between March and May
2009. The study group comprised patients who had visited our
outpatient clinic and electrocardiographic exercise testing was
planned to detect ischaemia. All patients had a history of either
exercise-induced angina or atypical angina. Patients with previ-
ous myocardial infarction, previous revascularisation, chronic
kidney failure, known malignancy, serious peripheral arterial
disease, heart failure, valvular heart disease, previous cerebro-
vascular accident, known chronic inflammatory conditions and
with active infectious diseases were excluded from the study. The
local ethics committee approved the study and informed written
consent was obtained from all patients.
Exercise testing
According to the current guidelines, patients discontinued medi-
cines that could affect the exercise testing 48 hours before the
test.
18
Patients performed the exercise test after a three-hour fast
and they were not allowed to drink tea/coffee or smoke before the
test. All patients underwent a standard exercise stress test using
the modified Bruce protocol.
Blood pressure, heart rate and 12-lead ECGs were recorded
at rest, during each stage of exercise, at peak exercise, and
for at least five minutes in the recovery phase. The ECG and
ST-segment depression were continuously displayed and meas-
ured automatically by a computer-assisted system (Marquette-
Case treadmill system, General Electric, Milwaukee, USA) in
all 12 leads.
The subjects were exercised until one of the end-points was
reached: age-specific target heart rate, or the development of
symptoms necessitating termination of the test. Patients were
encouraged to perform to their maximum effort and symptoms
that developed during the test were recorded. The development
of 0.10 mV (1 mm) or more of J-point depression measured from
the PQ junction, with a relatively flat ST-segment slope (e.g. less
than 0.7–1 mV/sec), depressed 0.10 mV or more 80 ms after the
J point (ST 80) in three consecutive beats, with a stable baseline,
was considered to be an abnormal response.
Criteria for a positive exercise test were determined as an
abnormal ST-segment response, or other criteria for positive
exercise testing [drop in systolic blood pressure
>
10 mmHg
from baseline blood pressure despite an increase in workload,
when accompanied by other evidence of ischaemia; moderate to
severe angina; sustained ventricular tachycardia; ST elevation (
≥
1.0 mm) in leads without diagnostic Q waves (other than V1 or
avR)].
18
Patients with a positive exercise test were placed in the
positive exercise group. Patients who did not meet the positive
criteria were not considered to have ischaemia and were put in
the negative exercise group.
In order to detect the ischaemic aetiology, coronary angio-
graphy was performed on an outpatient basis on all patients in
the positive exercise group on another suitable day. Stenosis that
reduced the lumen diameter by 50% in a coronary artery was
accepted as a haemodynamically significant lesion.
Blood sampling and biochemical analysis
Venous blood samples were taken from the antecubital veins
of patients before and 15 minutes after the exercise test. Blood
samples were taken in standard heparinised and non-heparinised
tubes. Samples were centrifuged at 3 500 rpm for 10 minutes.
Care was taken with the blood samples so as not to become
lipaemic or haemolysed. Centrifuged heparinised blood samples
were kept at –20°C.
SAA and hs-CRP were immediately assayed from the non-
heparinised blood samples using immunonephelometric assays
(Dade-Behring, BN II, Marburg, Germany). The reference
concentration for SAA was
<
5 mg/l and for hs-CRP it was
<
3mg/l. After collecting the samples, NT-proBNP (pg/ml) was
assayed using the immulite 1 000 chemiluminescence immuno-
assay system (Siemens Medical Solution Diagnostics, Deerfiled,
USA).
Statistical analysis
SPSS for Windows version 13.0 was used for statistical analysis.
Student’s t-test was used for comparison of mean values;
p
<
0.05
was accepted as significant.
Results
Of the 96 patients, 48 (18 women, 30 men) with positive exer-
cise tests were allocated to the positive exercise group and 48
(18 women, 30 men) with negative exercise tests were put into
the negative exercise group. There was a statistically significant
difference between the two groups for smoking, hyperlipidae-
mia, hypertension and family history of coronary heart disease
(Table 1).
Mean exercise duration was significantly longer in the nega-
tive exercise group than in the positive exercise group (11.5
±
1.1
vs 8.9
±
2.6 min,
p
<
0.001). Metabolic equivalents (METs) were
also higher in the negative exercise group than in the positive
group (12.3
±
1.5 vs 9.5
±
2.6,
p
<
0.001). There was no differ-
ence between the levels of hs-CRP, SAA and NT-proBNP before
and after exercise testing in both groups (Table 2).
The results of coronary angiography in the positive exer-
cise group of patients were as follows: there was single-vessel
disease in 21 patients, two-vessel disease in 11 patients, isolated
side-branch disease in five patients, triple-vessel disease in four
patients, left main coronary artery disease in two patients, left
main plus triple-vessel disease in two patients, coronary artery
ectasia in two patients, and spontaneous dissection of one coro-
nary artery in one patient.
Medical follow up was chosen in 28 patients as the main
TABLE 1. DEMOGRAPHIC FEATURESAND
RISK FACTORS OF PATIENTS
Positive exercise
testing
(
n
=
48) (%)
Negative exercise
testing
(
n
=
48) (%)
p
-value
Age (years)
57
±
10.0
57
±
7.0
>
0.05
Gender (female/male)
18/30
18/30
>
0.05
BMI (kg/m
2
)
27.7
±
3.7
28.9
±
4.2
>
0.05
Diabetes mellitus
16/48 (33)
14/48 (29)
>
0.05
Current smoker
30/48 (62)
18/48 (37)
<
0.03
Hypertension
44/48 (91)
18/48 (37)
<
0.001
Hyperlipidaemia
44/48 (91)
26/48 (54)
<
0.001
Family history
41/48 (85)
16/48 (33)
<
0.001
BMI: body mass index.
