JRSM >
Volume 97, Number 6 >
Pp. 275-278
1 Department of Cardiac Surgery, Alder Hey Hospital, Liverpool L12 2AP
2 Department of Cardiac Surgery, Harefield Hospital, Middlesex UB9 6JH, UK
Correspondence to: Mr Shahzad G Raja, Department of Cardiac Surgery, Royal
Liverpool Children's Hospital, Eaton Road, Liverpool L12 2AP, UK
E-mail:
drrajashahzad{at}hotmail.com
 | INTRODUCTION |
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 TOP INTRODUCTION PROS AND CONS OF...OFF-PUMP CORONARY ARTERY SURGERYCONCLUSIONREFERENCES |
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| PROS AND CONS OF CARDIOPULMONARY BYPASS |
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TOPINTRODUCTIONPROS AND CONS OF...OFF-PUMP CORONARY ARTERY SURGERYCONCLUSIONREFERENCES |
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Cardiopulmonary bypass allows the cardiothoracic surgeon to perform delicate work in a bloodless and motionless field. The surgeon achieves cardiac arrest by infusing a cold solution (cardioplegia) through the coronary artery circulation, and this solution is used throughout the operation to keep the heart motionless and cool. A cold solution is used because the heart tends to resume electrical activity at a normal temperature, and also because it uses less metabolic energy when cold.3
Drawbacks of cardiopulmonary bypass
Against the benefits of allowing a bloodless and motionless operating
field, cardiopulmonary bypass has the drawback of activating many cascades,
including inflammation and coagulation, with effects resembling an acute,
massive, defence
reaction.4 Under
normal circumstances these cascades offer protection from injury; however,
during cardiopulmonary bypass the whole-body response is non-physiological.
The components of this systemic inflammatory response syndrome include a
consumptive
coagulopathy,5
release into the circulation of more than seventy hormones, cytokines,
chemokines, vasoactive substances, cytotoxins, reactive oxygen species and
proteases of the coagulation and fibrinolytic
systems,6 induction
of interstitial fluid shifts, generation of microemboli, and temporary
dysfunction of nearly every
organ.7 These
effects arise primarily from the interaction between blood and nonendothelial
surfaces; the non-pulsatile nature of blood-flow during bypass and other
physiology disturbances contribute less to disruption of the milieu
interieur.4
Clearly, since many patients recover well after cardiopulmonary bypass, the body's physiological reserves and inhibitory pathways are capable of preventing wide-spread organ damage after heart operations.8 Today, however, operations are increasingly being done on high-risk patients with limited physiological reserves—for example, those with borderline organ functions and those who will need a long time on cardiopulmonary bypass and will therefore be especially susceptible to the potential adverse effects of the systemic inflammatory response syndrome. An uncontrolled inflammatory response seems to contribute substantially to the acute pulmonary, cardiovascular, neurological, splanchnic, haematological and immunological dysfunction observed after surgery under cardiopulmonary bypass. Moreover there is evidence, less well documented, that it contributes to subacute sequelae such as postoperative fever, postcardiotomy pericarditis and pleural effusions.9
| OFF-PUMP CORONARY ARTERY SURGERY |
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TOPINTRODUCTIONPROS AND CONS OF...OFF-PUMP CORONARY ARTERY SURGERYCONCLUSIONREFERENCES |
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The usual approach to multivessel grafting without cardiopulmonary bypass, OPCAB surgery, is via a standard median sternotomy.11 Other incisions are used12 but median sternotomy has the advantages of providing access to most regions to be revascularized and allowing standard techniques for internal mammary artery harvesting and emergency management.13 OPCAB surgery is sometimes employed as a hybrid procedure with percutaneous transluminal coronary angioplasty.13
Little displacement of the heart is needed to expose the left anterior descending artery, its diagonal branches or the proximal right coronary artery. However, exposure of the circumflex artery, its branches, the posterior descending artery and the posterolateral branch of the right coronary artery demands a combination of manoeuvres and techniques including pericardial sutures or a retracting sock.13 To elevate the heart anteriorly, when an anastomosis is being performed on the lateral wall, haemodynamics may be compromised by compression of the heart against the right pleura; this can be lessened by tilting and rotating the operating table and opening the right pleura. In the early days of OPCAB, bradycardia was induced with drugs (beta-blockers, diltiazem) to quieten the site of anastomosis. Today, the site is stabilized by pressure or suction devices.13
Clinical studies
The theoretical advantages of off-pump coronary artery surgery might lead
one to expect lower mortality and morbidity, less blood transfusion, faster
recovery, shorter hospital stays and lower
costs.1,14-17
However, the evidence is short of proof. To date, six large randomized trials
(
150 patients) of on-pump versus off-pump surgery have been completed and
have shown either no outcome differences or only small differences. Straka
et al.,18
in their study of 400 non-selected patients (mean age 63 years), found that
OPCAB patients had significantly fewer distal anastomoses (2.3 versus 2.7),
less blood loss (560 versus 680 mL), lower postoperative creatine kinase MB
(0.15 versus 0.56 microkat/L) and lower total hospital costs 
3,451
versus 4,387). They concluded that an off-pump technique is applicable
in 85% of non-selected patients and is at least as clinically safe and
effective as on-pump surgery. The study by Légaré et
al.19 is a
trial of 300 selected good-risk patients (out of 933 eligible for
randomization). The outcomes were excellent for both groups (1% mortality),
and no significant differences in morbid events were noted, including such
end-points as transfusion requirement, intubation time, intensive-care time,
and hospital stay. Gerola et
al.,20 in
their multicentre prospective study of 160 patients with lesions in the left
descending artery, alone or associated with the right coronary artery, did not
find any statistical difference in hospital mortality and morbidity between
the two myocardial revascularization techniques.
In a single-surgeon study, Puskas et al.21 recorded similar (low) mortality and stroke rates for on-pump and off-pump patients, but found the off-pump groups had lower transfusion rates and less enzyme release. A randomized trial from the UK documented lower hospital stay and a decreased risk of atrial fibrillation and blood transfusion for the off-pump group but equivalent mortality and stroke rates.22 Van Dijk et al.23 randomized 281 low-risk patients and found blood utilization slightly higher in the on-pump group, as was enzyme release. Follow-up at 1 year after operation showed no neurocognitive differences.24 The randomized trials that exist, therefore, have involved good-risk or standard-risk patients and have documented low procedure-related risk for both treatments. They have also shown equivalent revascularization rates in terms of mean numbers of grafts performed per patient.
Other studies of on-pump versus off-pump surgery have lacked randomized
controls, have included different types of patients and have yielded different
conclusions. In some large-database observational studies, attempts were made
to adjust for risk, so as to allow for bias in treatment selection. Al-Ruzzeh
et al.25
reviewed the UK database for 1997-2001 and found significant differences in
mortality and neurological, pulmonary, and renal complications, all in favour
of off-pump surgery. A report from the Society of Thoracic Surgeons National
Database by Cleveland et
al.26 noted a
decreased risk of death and neurological, renal, respiratory, and bleeding
complications in their off-pump group. Similarly, Mack et
al.,27 in
their retrospective analysis of all coronary artery bypass grafting in a
3-year period in four centres with off-pump coronary surgery experience,
showed that cardiopulmonary bypass was predictive of mortality in high-risk
patients including reoperations, female patients, and patients aged 75
years. Off-pump coronary artery bypass grafting, on the other hand, was
associated with less morbidity, including significantly lower rates of blood
transfusion (32.6% versus 40.6%), stroke (1.4% versus 2.1%), renal failure
(2.6% versus 5.2%), pulmonary complications (4.1% versus 9.5%), reoperation
(1.7% versus 3.2%), atrial fibrillation (21.1% versus 24.99%), and
gastrointestinal complications (3.6% versus 4.8%).
High-risk patients
From existing evidence, it is conceivable that a more challenging patient
category might benefit most from OPCAB surgery. Data from nonrandomized
studies show that OPCAB surgery can be safely performed in high-risk patients
with multivessel coronary artery
disease.28-32
The crucial advantage of off-pump surgery might be a lower risk of
perioperative stroke, a major cause of which, in on-pump surgery, is
dislodgment of atheromatous plaque by cannulation and clamping of the
ascending aorta.33
The presence of aortic atherosclerosis greatly increases the risk of stroke,
and aortic atherosclerosis is especially likely in the old, in people with
three-vessel disease, and in people with
diabetes.33 In CABG
patients older than 80 years, the risk of stroke was as high as
9%.35 Since OPCAB
does not necessitate manipulation of the
aorta36 and avoids
the potential risks of cardiopulmonary bypass, we might reasonably expect it
to decrease the risk of
stroke.36,37
Contraindications
The contraindications to OPCAB surgery are even more uncertain. Selection
criteria vary from surgeon to surgeon, and the proportion of patients
considered suitable for an OPCAB procedure ranges from 0% to 99%, depending on
the skills and opinions of the surgeon and the policy of the institution. To
do an OPCAB procedure in a haemodynamically unstable patient is probably
unwise but many surgeons no longer consider multivessel disease, diffuse
coronary vessel disease, or emergency surgery contraindications. The most
important contraindication, therefore, seems to be the situation in which a
surgeon feels uncomfortable with an OPCAB procedure in a specific patient with
a specific coronary anatomy. Concerns have been raised about incomplete
revascularization and suboptimal anastomoses with the potential for early
occlusion.14
However, collective data on graft patency after OPCAB are
necessary.20,38,39
Occasionally, during a beating heart operation, the patient must be placed on cardiopulmonary bypass in order to safely complete the operation. Common reasons mandating conversion from an off-pump to an on-pump procedure include haemodynamic instability, failure to adequately expose the target vessel, deep intramyocardial course of the target vessel, and global ventricular ischaemia. The reported incidence of conversion to CPB ranges from a low of 1.1% to a high of 16.3%.40 Patients who require conversion may be at greater risk of complications or death, and the procedure will cost more.40
| CONCLUSION |
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TOPINTRODUCTIONPROS AND CONS OF...OFF-PUMP CORONARY ARTERY SURGERYCONCLUSIONREFERENCES |
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| REFERENCES |
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TOPINTRODUCTIONPROS AND CONS OF...OFF-PUMP CORONARY ARTERY SURGERYCONCLUSIONREFERENCES |
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  S. G Raja and G. D Dreyfus Current Status of Off-pump Coronary Artery Bypass Surgery Asian Cardiovasc Thorac Ann, April 1, 2008; 16(2): 164 - 178. [Abstract] [Full Text] [PDF]
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