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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 1, January/February 2017
AFRICA
31
Finally, 760 patientswere divided into two groups: ONBHCAB
(group 1) or OPCAB (group 2). To adjust for baseline differences
in parameters between the groups, a propensity score analysis
was carried out and a total of 398 patients were included:
ONBHCAB (
n
=
181), OPCAB (
n
=
217).
Patients’ pre-operative characteristics, such as age and
gender, smoking status, hypertension, diabetes mellitus (DM),
dyslipidaemia, obesity (body mass index
>
30 kg/m²), chronic
obstructivepulmonarydisease(COPD),historyof stroke,peripheral
vascular disease (PVD), history of myocardial infarction (MI),
unstable angina pectoris (USAP), EuroSCORE (European System
for Cardiac Operative Risk Evaluation) risk score, left ventricular
dysfunction, history of percutaneous coronory intervention (PCI),
number of diseased vessels, and the presence of left main coronary
artery (LMCA) stenosis were recorded.
Definitions
Vessel disease was defined as stenosis of more than 50% of
the major epicardial coronary arteries. Estimated creatinine
clearance (CrCl) rate was calculated using the Cockcroft–Gault
formula: CrCl (ml/min)
=
[(140–age)
×
weight (kg)]/[serum
creatinine (mg/dl)
×
72]
×
0.85 for women, from baseline blood
samples. PVD was defined as a stenosis of 50% or more affecting
any non-coronary vasculature.
Left ventricular dysfunction was defined as moderate [ejection
fraction (EF) 0.30–0.49%] or severe (EF
<
0.30%). Complete
revascularisation was defined as treatment of all major coronary
arteries [left anterior descending (LAD), circumflex (Cx) and
right coronary artery (RCA)]
≥
50% diameter stenosis.
Total blood loss was defined as the sum of the mediastinal
and chest tube drainage in the first 48 hours. Consumed units
of red blood cells (RBC) was defined as the sum of the blood
units used during the hospital stay. Any inotropic support
started in the peri-operative period, even low doses of dopamine
infusion due to haemodynamical instability, was determined
as peri-operative need for inotropic support. Peri-operative MI
was defined as cTnI
>
5
µ
g/l during the hospital stay with new
ECG change or echocardiographic evidence of new
regional wall
motion abnormality.
8
Renal complication was defined as at least
100% increase
in basal serum creatinine level. Pulmonary complication was
defined as pleural effusion, atelectasis, phrenic nerve paralysis,
diaphragmatic dysfunction, pneumonia, acute respiratory
distress syndrome, pneumothorax or chylothorax. Neurological
complication was defined as any new transient ischaemic attack
(TIA), stroke or encephalopathy occurring in the peri-operative
period.
Early rehospitalisation was defined as any hospitalisation
due to CABG-related complications (such as sternal dehiscence,
mediastinitis) or cardiovascular problems (such as MI, congestive
heart failure, rhythm disturbance, neurological complications,
pulmonary embolism). Early re-operation was defined as
re-operation due to bleeding or cardiac tamponade and graft
failure.
Surgical procedures
All procedures were performed by the same surgeon, who
made the decision to perform OPCAB or ONBHCAB surgery.
Classic median sternotomy, left internal thoracic artery (LIMA)
harvesting and other conduit preparations were performed
according to a standard technique. In patients undergoing
OPCAB, heparin was administered to keep the activated clotting
time (ACT) greater than 300 seconds.
Distal anastomoses were performed by end-to-side or side-to-
side techniques with a running 7/0 Prolene suture, using a local
myocardial stabiliser (Octopus, Medtronic Inc, Minneapolis,
MN, US). Proximal coronary clamping of all target vessels
was performed with Mueller atraumatic vascular clamps (0.5
Newton); distal occlusion was never performed. Insufflation of
filtered room air (
<
5 l/min) was used to provide better visibility
during anastomosis. During distal anastomosis and reperfusion,
2 ml
/
kg 20%
mannitol was administered. All proximal
anastomoses were performed under single side clamping using
6/0 prolene sutures.
At the end of surgery, heparin was neutralised with protamine,
ensuring that the ACT was between 150 and 180 seconds. In
the early postoperative period (6–8 hours), low molecular-
weight heparin and 100 mg acetylsalicylic acid were commenced
routinely.
In patients undergoing ONBHCAB, heparin was administered
to keep the ACT above 450 seconds. CPB was established with
an ascending aortic arterial cannula and a right atrial two-stage
venous cannula, using a membrane oxygenator and a roller
pump. All patients were cooled to 32–34°C. Mean arterial blood
pressure was maintained in the range of 60–90 mmHg. Distal
anastomoses were performed by end-to-side or side-to-side
techniques with a running 7/0 prolene suture, using a myocardial
stabiliser device (Octopus, Medtronic Inc, Minneapolis, MN,
US). Proximal anastomoses were performed using a 6/0 prolene
suture during the heating period with the assistance of an
ascending aortic side-clamp. After the completion of CPB
and cannula removal, heparin was neutralised with protamine,
providing an ACT
<
150 seconds. Acetylsalicylic acid at a dose
of 100 mg and low molecular-weight heparin was initiated at the
postoperative 24th hour.
The primary endpoint of this study was to compare the early
and long-term MACE rates, defined as cardiac related or sudden
death, MI, the need for repeat revascularisation, and stroke
following ONBHCAB versus OPCAB. The secondary endpoint
was to identify independent predictors of long-term MACE
in these groups of patient. Long-term follow up was obtained
through out-patient clinic visits, hospital records and phone
calls. All-cause mortality (patient death reported by patients’
relatives or hospital records) and MACE were determined.
Statistical analysis
Continuous variables are expressed as mean
±
standard deviation.
Categorical variables are expressed as percentages. A propensity
score analysis was carried out to control selection based on
the baseline variables. The Mann–Whitney
U
-test was used to
compare non-parametric continuous variables, the Student’s
t
-test was used to compare parametric continuous variables, and
the chi-squared test was used to compare categorical variables.
Cumulative survival curves for long-term MACE were
constructed using the Kaplan–Meier method, whereas
differences between the groups were evaluated with log-rank
tests. Multivariate logistic regression analysis was used to identify