CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 2, March/April 2011
AFRICA
87
therapeutic modality, whereas 14 patients underwent percutane-
ous coronary intervention and were discharged one day after the
procedure with appropriate medication. In six patients, an aorto-
coronary bypass grafting operation was successfully performed.
No surgery-related complications occurred and all of the patients
were discharged uneventfully.
Discussion
In this study, we observed a slight non-significant rise in the
serum levels of hs-CRP, SAA and NT-proBNP with exercise.
Although the increase in serum SAA, hs-CRP and NT-proBNP
levels during exercise testing was slightly more in the positive
exercise group, the difference was not significant. We concluded
that serum levels of hs-CRP, SAA and NT-proBNP could not
predict the occurrence of reversible myocardial ischaemia during
exercise.
Shehadeh
et al
. reported that there was no relation between
hs-CRP and transient myocardial ischaemia in patients with a
history of chronic heart failure or previous myocardial infarc-
tion.
7
They also found that exercise duration was longer in
patients with lower levels of hs-CRP. In our study, although basal
serum hs-CRP levels were the same in the two groups, the exer-
cise capacity of the non-ischaemic group was better than in the
ischaemic group. Veleska
et al
. could not find any relationship
between serum hs-CRP levels and exercise testing results in a
study that included 200 patients with positive exercise tests.
8
On
the other hand, Cosin-Sales
et al
. reported a correlation between
serum hs-CRP levels and ST-segment depression during exercise
testing with Holter monitoring, and the frequency of angina
episodes in patients with typical chest pain and normal coronary
angiograms.
6
Therefore, the relationship between hs-CRP and
reversible myocardial ischaemia was not as clear as in unstable
coronary artery disease and needs to be clarified in large-scale
studies.
High-density lipoprotein (HDL) is the main carrier of SAA
in plasma. In cases of low HDL status, SAA is carried by the
other apolipoproteins.
19-21
SAA may comprise up to 80% of HDL
during inflammation, which results in deterioration of the anti-
atherogenic properties of HDL.
19-21
Ogasawara
et al
. reported that
HDL molecules rich in SAA are a risk factor for cardiovascular
diseases, therefore the SAA/LDL complex was found to be
directly related to high cardiovascular risk.
22
In both groups in our study, serum SAA levels increased
slightly after exercise testing but there was no significant differ-
ence. The increase in SAA levels seemed not to be associated
with myocardial ischaemia. We also could not find any study
addressing the relationship between SAA and transient myocar-
dial ischaemia in the literature.
Early studies reported a decrease in serum inflammatory
biomarker levels in subjects who exercised regularly.
23
However,
during short, sudden exercise, the immune system becomes acti-
vated and inflammatory biomarker levels elevate in the serum.
This mechanism has not been clarified.
23
The possible mecha-
nisms are: muscle damage during exercise, new developing
oxidative stress as a response to the increase in oxygen demand
with the forced usage of muscles, and increased interleukine-6
(IL-6) synthesis in muscles.
Firstly, the increase in serum CRP and SAA levels during
exercise may be due to increased synthesis of IL-6. In addition,
leucocyte counts increase during exercise.
24
As a result, these
changes may trigger immune system activation and increased
levels of acute-phase reactants. In our study, serum SAA levels
increased, as did serum hs-CRP levels after exercise in both the
ischaemic and non-ischaemic groups. But we felt these eleva-
tions were as a result of exercise-induced immune system activa-
tion and did not reflect myocardial ischaemia.
NT-proBNP is the inactive form of BNP. Like other natriu-
retic peptides, the serum concentration of NT-proBNP increases
as a response to increased left ventricular myocardial wall
stress.
25,26
NT-proBNP levels increased in patients with disorders
causing left ventricular diastolic dysfunction, but this increase
in NT-proBNP was not as much as that seen in left ventricular
systolic dysfunction.
27
In recent years, increased NT-proBNP synthesis has been
shown as a response to myocardial ischaemia. In addition, it has
also been shown that increases in NT-proBNP levels were related
to the extent and severity of the coronary artery disease.
28
Serum
NT-proBNP was found to be a strong predictor for future cardio-
vascular events in patients with stable angina pectoris.
29
Some studies were designed for detecting the correlation
between NT-proBNP and transient myocardial ischaemia. Kurz
et al
. found that baseline NT-proBNP levels were higher in
patients with transient ischaemia; however there was no corre-
lation between NT-proBNP levels and ischaemia after exercise
testing.
30
In another study which was done with myocardial
perfusion scintigraphy, Staub
et al
. reported that NT-proBNP
levels before and after exercise were significantly higher in
patients who developed transient ischaemia.
31
Sabatin
et al
. and
Foote
et al
. also reported similar results.
32,33
On the other hand,
other studies reported contradictory findings.
34,35
In a study,
before and after exercise testing, serum NT-proBNP levels were
studied hourly for six hours and NT-proBNP levels were not
found to be correlated with myocardial ischaemia.
36
In our study, we could not find any relationship between tran-
sient myocardial ischaemia and serum NT-proBNP levels before
and after exercise testing. In both ischaemic and non-ischaemic
patients, serum NT-proBNP levels increased slightly after exer-
cise testing. This might have been caused by a mechanism other
than ischaemia. In a study on healthy adults, an increase in serum
NT-proBNP levels was shown after electrocardiographic exercise
testing.
37
It was concluded that these increases after exercise test-
TABLE 2. SERUM HS-CRP, SAAAND NT-proBNP LEVELS BEFOREANDAFTER EXERCISE TESTING
Positive exercise testing (
n
=
48)
Negative exercise testing (
n
=
48)
p
-value
Pre-test
Post-test
Pre-test
Post-test
Hs-CRP (mg/l)
4.1
±
6.2
4.9
±
6.5
1.9
±
1.3
2.7
±
1.7
>
0.05
SAA (mg/l)
8.4
±
12.3
10.0
±
14.0
5.8
±
4.2
6.2
±
4.1
>
0.05
NT-proBNP (pg/ml)
175.1
±
392.3
201.5
±
461.6
92.2
±
130.5
102.5
±
139.2
>
0.05
hs-CRP: high-sensitivity C-reactive protein, SAA: serum amyloid-associated protein, NT-proBNP: N-terminal proBNP.
