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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 1, January/February 2017
34
AFRICA
Studies comparing the outcomes of OPCAB versus
ONBHCAB are however limited.
5
Therefore we evaluated early
outcomes and long-term MACE rates of ONBHCAB versus
OPCAB in a matched population. All patients were operated
on by the same surgeon, therefore positioning of the heart
and anastomosis techniques were typically similar between the
groups, except for the use of CPB.
The need for inotropic agents or IABP were found to be
similar between the groups. Moreover, no difference was detected
in terms of incidence of peri-operative MI and AF between the
two techniques. These findings indicate that both OPCAB and
ONBHCAB techniques may cause similar myocardial damage,
which may explain the blood loss during both procedures.
Stroke is generally considered the most important coronary
surgery-related morbidity. Many meta-analyses have revealed that
OPCAB is associated with short- and long-term benefits in stroke
prevention, especially in higher-risk patients.
1,13
By contrast,
Moller and co-workers’ meta-analysis revealed no significant
benefit of OPCAB compared with ONCAB regarding stroke.
14
In our study, no significant difference was detected among the
groups in terms of peri-operative stroke, TIA or encephalopathy.
These findings revealed that the avoidance of aortic cross-
clamping may reduce embolic particles. The duration of
ventilation, and ICU and hospital stays were significantly
shorter in the OPCAB group, as in previous publications.
15-17
The
amount of drainage in the first 48 hours was significantly lower
in the OPCAB group, therefore, the mean number of transfused
RBC units was significantly lower in the OPCAB group. These
findings may be explained by the well-known adverse effects of
extracorporeal circulation and hypothermia on the coagulation
system.
15-17
Chaudhry’s meta-analysis
7
revealed similar renal dysfunction
after ONBHCAB in comparison with CCAB. In our study,
despite similar pre-operative levels of EF, CrCl and peri-
operative LCO, the OPCAB group showed significantly lower
renal complications than the ONBHCAB group. This finding
supports a previous report indicating the independent negative
effect of CPB on renal function.
18
Two different meta-analyses of randomised trials reported a
significantly lower number of distal anastomoses performed per
patient following off-pump versus on-pump surgery.
7,19
Similarly,
in our study, the number of distal anastomoses per patient was
significantly lower in the OPCAB group. However, in terms of
functionally incomplete revascularisation, no difference was
detected between the groups. It is clear that the advantage of
haemodynamic stability of ONBHCAB made the surgeon
feel more at ease than with OPCAB and he performed better
anastomoses.
Two different meta-analyses of randomised trials revealed no
significant differences between off-pump and on-pump CABG
regarding all-cause mortality and MACE.
7,8
Our study also
revealed similar all-cause mortality rates between the groups, the
OPCAB group showing a significantly better MACE-free period,
including MI, PCI, redo CABG and stroke
in the long term.
Moreover, we found that the mean number of transfused RBC
units was the only significant predictor of MACE following
CABG. This was considered the main cause of the negative
results in the ONBHCAB group.
It is clear that CPB is a challenge to the haematopoietic
system due to haemodilution, significant shifts in intravascular
volume, mechanical trauma to the blood cells and hypothermia,
leading to increased transfusion of RBC or blood products.
2,13,15,16
Transfusion of RBC as a risk factor for early mortality following
CABG has been well established, whereas the effect of RBC
transfusion on late mortality or MACE is less well described.
A number of studies have shown the negative impact of RBC
transfusion on early cardiovascular events and late mortality
rates following cardiac surgery.
20-22
RBC transfusion was also
found to be associated with peri-operative MI following elective
isolated OPCAB.
23
Additionally, a recent report showed that
low-risk patients had a significantly higher long-term mortality
rate when receiving RBC following cardiac surgery, compared
with patients who did not receive transfusions. This effect was
not seen in high-risk patients, suggesting the negative impact
of the use of blood was independent of other risk factors.
24
RBC transfusion was also found to be associated with a
strongly increased risk of both 30-day cardiovascular events and
mortality in elective vascular surgery patients.
25
The reasons for such a correlation between long-term
cardiovascular events and blood transfusion are unclear but
the
pro-inflammatory properties of transfused RBC have
been suggested as a potential explanation.
It has been well
established that inflammation plays a major role in all stages
of atherogenesis. The role of inflammation in the pathogenesis
of ischaemic stroke,
26
MI and neo-intimal hyperplasia leading
to in-stent restenosis
27
or graft failure
28
has also been described.
Moreover, Fransen
et al
. showed that blood transfusion may
potentialise the inflammatory effect of CPB.
29
The combined
effect of RBC transfusion and CPB may therefore aggravate
atherosclerosis by stimulating the ongoing inflammatory process
in patients with coronary artery disease.
The present study has some limitations, including its
retrospective, non-randomised design and relatively small sample
size. However, our population contained propensity-matched,
homogeneous patients undergoing CABG surgery by the same
surgeon, using the same technique, ONBHCAB. Therefore, other
factors interacting with the frequency of MACE due to differences
in surgical technique or patient demographics were excluded.
Conclusion
Off-pump CABG provided better long-termMACE-free survival
compared with on-pump beating-heart CABG. Decreased
incidence of blood transfusion following OPCAB surgery may
have been the main reason for this.
References
1.
Afilalo J, Rasti M, Ohayon SM, Shimony A, Eisenberg MJ. Off-pump
vs on-pump coronary artery bypass surgery: an updated meta-analysis
and meta-regression of randomized trials.
Eur Heart J
2012;
33
(10):
1257–1267.
2.
Angelini GD, Taylor FC, Reeves BC, Ascione R. Early and midterm
outcome after off-pump and on-pump surgery in Beating Heart Against
Cardioplegic Arrest Studies (BHACAS 1 and 2): a pooled analysis of
two randomised controlled trials.
Lancet
2002;
359
: 1194–1199.
3.
Saba D, Gören S, Tekin BH,
Ş
enkaya I, Ercan A, Özkan H,
et al.
The
effects of position, ischemia and reperfusion to hemodynamics on
the beating heart coronary bypass
.
Turk Gogus Kalp Damar Cerrahisi
Dergisi
2003;
11
(1): 26-31.