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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 26, No 6, November/December 2015
238
AFRICA
injury score and net release of cTnI and hs-cTnT in the post-ACC
period. No correlation was found between myocardial injury
score and net release of CK-MB and CK-MB mass (Table 5).
We analysed the relationship between apoptotic index,
myocardial injury score and intra-operative data. We found a
significant positive correlation between apoptotic index and
ACC time, CPB time and number of grafted vessels (Table 6).
A significant positive correlation was found between myocardial
injury score and ACC time, CPB time and number of grafted
vessels (Table 6).
Additionally, when the relationship between net release of
cardiac markers in the post-ACC period and the intra-operative
data were analysed, a positive correlation was observed between
net release of hs-cTnT and ACC time. Furthermore, a positive
correlation was found between net release of hs-cTnT and CPB
time (Table 7). No correlation was found between peri-operative
data and net release of other cardiac markers in the post-ACC
period (Table 7).
Discussion
CABG is a highly complex and risky surgical procedure, and
despite well-established myocardial protective procedures, CABG
surgery may still cause myocardial damage.
14
The incidence of
PMI varies considerably, from three to 30%, because of different
diagnostic criteria and variable patient populations.
15
Although
changes in blood concentrations of cardiac markers, such as
CK-MB, myoglobin (Mb) and cardiac troponins are used in the
diagnosis of PMI, there are no widely accepted standardised
diagnostic criteria.
16
Myocardial damage causes disruption of the normal cardiac
myocyte membrane integrity and loss of intracellular content
into the extracellular space. Therefore, elevated levels of cytosolic
and structural proteins, such as CK-MB and cardiac troponins,
can be detected in the blood.
17
Interpretation of cardiac biomarkers is difficult after CABG
surgery because the specificity of some cardiac markers during
CABG surgery is limited, depending on skeletal muscle injury
occurring in the surgical procedure. Skeletal muscle injury may
increase intra-operative concentrations or activities of some
cardiac markers, such as CK-MB and CK-MB mass. As a result,
increases in these markers due to skeletal muscle damage may
confound the diagnosis of PMI. Consequently, it is important
to detect PMI using a highly specific marker.
18
In this study, the
relationship between myocardial apoptosis and injury and the
Table 2. Comparison of the cardiac marker values in arterial and coronary
sinus blood samples between the pre-ACC and post-ACC period
Cardiac
markers
Pre-ACC
arterial
blood
Post-ACC
arterial
blood
p
-value
Pre-ACC
coronary
sinus blood
Post-ACC
coronary
sinus blood
p
-value
CK-MB (U/l)
16.4
42.0
<
0.001 19.7
51.5
<
0.001
(12.0–21.0) (32.0–73.0)
(14.8–24.0) (35.7–85.5)
CK-MB mass
6.5
21.0
<
0.001
7.3
25.0
<
0.001
(
µ
g/l)
(5.5–10.4) (15.5–28.0)
(6.0–12.5) (17.5–34.0)
cTnI (
µ
g/l)
0.12
0.25
<
0.01
0.14
0.31
<
0.01
(0.07–0.3) (0.13–0.42)
(0.08–0.29) (0.17–0.49)
hs-cTnT (ng/l)
125.0
193.0
<
0.05
159.0
239.0
<
0.05
(59.5–211.6) (91.0–309.0)
(66.0–230.7) (95.5–425.0)
ACC: aortic cross-clamping; CK-MB: creatine kinase isoenzyme MB; cTnI: cardiac
troponin I; hs-cTnT: high-sensitivity cardiac troponin T. Data are presented as
median and interquartile ranges for each group. Data were tested using the Mann–
Whitney
U
-test. A
p
-value
<
0.05 was considered statistically significant.
Table 3. Comparison of the net release of cardiac markers
between the pre-ACC and post-ACC period
Cardiac markers Pre-ACC net release Post-ACC net release p-value
CK-MB (U/l)
3.0
7.0
<
0.001
(1.8–5.0)
(2.9–15.0)
CK-MB mass
1.0
2.0
<
0.001
(
µ
g/l)
(0.5–1.4)
(2.0–4.0)
cTnI (
µ
g/l)
0.02
0.03
<
0.01
(0.01–0.04)
(0.02–0.06)
hs-cTnT (ng/l)
15.0
26.0
<
0.05
(5.4–42.0)
(9.5–79.6)
ACC: aortic cross-clamping; CK-MB: creatine kinase isoenzyme MB;
cTnI: cardiac troponin I; hs-cTnT: high-sensitivity cardiac troponin
T; pre-ACC: just before aortic cross-clamping; post-ACC: within
15 minutes of aortic declamping. The net releases of cardiac mark-
ers were quantified as the arteriovenous difference (coronary sinus
concentration minus arterial concentration). Data are presented as
median and interquartile ranges for each group. Data were tested
using the Mann–Whitney
U
-test. A
p
-value
<
0.05 was considered
statistically significant.
Table 5. The relationship between apoptotic index (TUNEL),
histopathological myocardial injury score and net release of
cardiac marker values in the post-ACC period
CK-MB
(U/l)
CK-MB
mass (
µ
g/l)
cTnI
(
µ
g/l)
hs-cTnT
(ng/l)
Apoptotic index
(TUNEL)
r
=
0.222
p
=
0.185
r
=
0.013
p
=
0.937
r
=
0.283
p
=
0.090
r
=
0.507
p
=
0.001*
Myocardial
injury score
r
=
0.260
p
=
0.120
r
=
–0.107
p
=
0.530
r
=
0.333
p
=
0.044*
r
=
0.416
p
=
0.010*
ACC: aortic cross-clamping; CK-MB: creatine kinase isoenzyme MB;
cTnI: cardiac troponin I; hs-cTnT: high-sensitivity cardiac troponin T;
TUNEL: terminal deoxynucleotidyl transferase-mediated deoxyuri-
dine triphosphate nick end-labelling; post-ACC: within 15 minutes of
aortic declamping. Net release of cardiac markers was quantified as
arteriovenous difference (coronary sinus concentration minus arterial
concentration). Relationships between data were tested using Spear-
man’s correlation analysis. *A
p
-value
<
0.05 was considered statisti-
cally significant.
Table 4. The relationship between apoptotic index (TUNEL),
histopathological myocardial injury score and cardiac
marker values in arterial and coronary sinus blood
samples in the post-ACC period
CK-MB
(U/l)
CK-MB
mass (
µ
g/l)
cTnI
(
µ
g/l)
hs-cTnT
(ng/l)
Arterial blood samples
Apoptotic index
(TUNEL)
r
=
0.019
p
=
0.910
r
=
0.422
p
=
0.009*
r
=
0.611
p
<
0.001*
r
=
0.809
p
<
0.001*
Myocardial
injury score
r
=
0.021
p
=
0.900
r
=
0.316
p
=
0.057
r
=
0.544
p
<
0.001*
r
=
0.719
p
<
0.001*
Coronary sinus blood samples
Apoptotic index
(TUNEL)
r
=
0.085
p
=
0.616
r
=
0.358
p
=
0.030*
r
=
0.623
p
<
0.001*
r
=
0.790
p
<
0.001*
Myocardial
injury score
r
=
0.087
p
=
0.606
r
=
0.223
p
=
0.184
r
=
0.554
p
<
0.001*
r
=
0.695
p
<
0.001*
ACC: aortic cross-clamping; CK-MB: creatine kinase isoenzyme MB;
cTnI: cardiac troponin I; hs-cTnT: high-sensitivity cardiac troponin
T; TUNEL: terminal deoxynucleotidyl transferase-mediated deoxy-
uridine triphosphate nick end-labelling; post-ACC: within 15 minutes
of aortic declamping. Relationships between data were tested using
Spearman’s correlation analysis. *A
p
-value
<
0.05 was considered
statistically significant.