Vol 24 No. 3-4

WHICH PATIENT SUBSET IS BEST SUITED FOR CABG

DR SOHAIL KHAN BANGASH

Coronary artery bypass graft surgery (CABG)has been the standard of care for revascularisation of patients with complex coronary artery disease since its introduction in 1968.When percutaneous coronary intervention (PCI)was  introduced in 1977,it was thought to be appropriate only for patients with single vessel disease,but as operator ability and device technologies have advanced,the use of PCI has expanded to treat patients with increasingly complex disease,such as multivessel and left main coronary disease.The optimum method for
revascularisation has been a matter of debate,with many published trials comparing outcomes
of CABG and PCI with drug-eluting stents (DES).Most of these trials have been limited by
non-randomised patient selection,inclusion of less complex disease,or insufficient statistical
power.

The SYNergy between percutaneous coronary intervention with TAXus and cardiac
surgery (SYNTAX)trial assessed the optimum revascularisation treatment for patients with
de-novo left main coronary disease or three-vessel disease (or both),by randomly assigning
patients to either PCI with a first-generation paclitaxel-eluting stent or CABG.For the primary
endpoint of major adverse cardiac and cerebro vascular events (MACCE)at 1 year,PCI did
not meet the goal of non-inferiority compared with CABG,because the PCI group had a
significantly higher rate of repeat revascularisation than did the CABG group.Rates of death
and myocardial infarction were similar between the two groups,and stroke was significantly
increased in the CABG group compared with the PCI group.At 3 years,rates of MACCE,
myocardial infarction,and repeat revascularisation were significantly higher in the PCI group
than in the CABG group,whereas rates of the composite safety endpoint of death or stroke or
myocardial infarction,and stroke alone,were not significantly different between treatment
groups.

5-year results of the SYNTAX trial,which compared coronary artery bypass graft surgery
(CABG)with percutaneous coronary intervention (PCI)for the treatment of patients with left
main coronary disease or three-vessel disease,were reported,to confirm findings at 1 and 3
years.1800 patients were randomly assigned to CABG (n=897)or PCI (n=903).More patients
who were assigned to CABG withdrew consent than did those assigned to PCI (50 vs 11).After
5 years ’follow-up,Kaplan-Meier estimates of MACCE were 26.9%in the CABG group and 37.3%in the PCI group (p<0.0001).Estimates of myocardial infarction (3.8%in the CABG
group vs 9.7%in the PCI group;p<0.0001)and repeat revascularization (13.7%vs 25.9%;
p<0.0001)were significantly increased with PCI versus CABG.All-cause death (11.4%in the
CABG group vs 13.9%in the PCI group;p=0.10)and stroke (3.7%vs 2.4%;p=0.09)were not
significantly different between groups.28.6%of patients in the CABG group with low
SYNTAX scores had MACCE versus 32.1%of patients in the PCI group (p=0.43)and 31.0%
in the CABG group with left main coronary disease had MACCE versus 36.9%in the PCI
group (p=0.12);however,in patients with intermediate or high SYNTAX scores,MACCE was
significantly increased with PCI (intermediate score,25.8%of the CABG group vs 36.0%of
the PCI group;p=0.008;high score,26.8%vs 44.0%;p<0.0001).CABG should remain the
standard of care for patients with complex lesions (high or intermediate SYNTAX scores).For
patients with less complex disease (low SYNTAX scores)or left main coronary disease (low
or intermediate SYNTAX scores),PCI is an acceptable alternative.All patients with complex
multivessel coronary artery disease should be reviewed and discussed by both a cardiac
surgeon and interventional cardiologist to reach consensus on optimum treatment.The
application of the SYNTAX score has created a new era in the objective assessment of
coronary artery disease complexity,making interpretation of previous trials with more crude
assessment of coronary severity difficult.

ASCERT,a large comparative-effectiveness study derived from Medicare and
professional society databases,found that CABG surgery provides better four-year survival
odds than PCI in high-risk stable patients with two-or three-vessel disease.Society of
Thoracic Surgeons (STS),the American College of Cardiology (ACC),and the Centers for
Medicare &Medicaid Services (CMS)collaborated to develop ASCERT.The ASCERT high-
risk subset results,show a long-term survival benefit for surgery over percutaneous
intervention.This confirms,in current real-world practice,the results of other studies,from the
New York state data to the randomized trials like SYNTAX.The study combines PCI data
from the National Cardiovascular Data Registry (NCDR),bypass surgery data from the STS
database,and up to four years of Medicare outcomes data (average 2.67 years)from CMS
(Centers for Medicare &Medicaid Services).Overall,the study includes 86 244 bypass-
surgery patients and 103 549 PCI patients treated from 2004 through 2007.The mean age was
74 years.The high-risk subset represented about 2%of the patients in the trial.Survival rates
favored percutaneous intervention within one year--about 1%vs 2%mortality for
percutaneous intervention vs surgery,respectively.But after one year,bypass surgery was
associated with progressively better survival than percutaneous intervention.For high risk
patients:75 or older,diabetic,ejection fraction <50%,and glomerular filtration rate <60
mL/min/1.73m2,bypass surgery was associated with lower four-year mortality than PCI (risk
ratio=0.72)However,this analysis is limited by a lack of prospective randomization and the unanswered question of whether selection bias can be adequately compensated for via
propensity adjusted statistical analyses.Additionally,the ASCERT study did not use a measure
of coronary disease severity,such as the SYNTAX score,and is thus limited in its ability to
provide comparative information for the optimum revascularisation method for a given level
of coronary anatomic complexity.In the SYNTAX trial,a significant difference in outcomes
depending on base line severity of coronary artery disease was noted.

The recently published FREEDOM (Future REvascularization Evaluation in patients with
Diabetes mellitus:Optimal management of Multivessel disease)trial,assessed CABG versus
PCI in 1900 patients with multivessel disease and diabetes.In the overall population of that
study,patients in the CABG group had significantly lower rates of the composite endpoint of
all-cause death,cerebrovascular accident,or myocardial infarction compared with patients in
the first-generation DES group (18 •7%in the CABG group vs 26 •6%in the PCI group;
p=0 •005).However,as in the SYNTAX study,the FREEDOM trial reported no difference
between treatment groups for the composite endpoint of all-cause death,cerebrovascular
accident,or myocardial infarction for patients with SYNTAX scores of lower than 22,and a
mortality benefit associated with CABG in patients with SYNTAX scores of 23 –32.However,
for patients with SYNTAX scores of 33 or higher in the FREEDOM trial,no significant
diference between treatment groups for this endpoint was reported.The reason for this
difference in outcomes is unclear,but might be related to statistical power,since less than 20%
of patients in the FREEDOM trial had a SYNTAX score of 33 or higher.

It is unclear how the overall results would differ with the use of fractional flow reserve or
newer-generation DES (with lower repeat revascularisation and associated stent thrombosis
rates)or improvements in antiplatelet therapy and CABG techniques (eg,more arterial
revascularisation,improved perioperative care).The EXCEL trial is investigating use of
newer-generation DES versus CABG in 2600 patients with low-risk or intermediate-risk left
main lesions,and results are expected to provide additional insight into the optimum
revascularisation technique in this subgroup of patients.

Diabetic patients experience more extensive atherosclerosis and a worse clinical outcome
following revascularization procedures.In recent years,technical advances have resulted in
improved outcomes after coronary revascularization with PCI or CABG.Much of the evidence
comparing PCI with CABG comes from older studies of PTCA,which did not use current
recommended antiplatelet therapies and aggressive secondary preventive strategies post-
revascularization.Data to guide decision making are limited regarding the current choice
between CABG and PCI using DES and newer antiplatelet agents in diabetic patients with multivessel CAD.Although CABG remains the standard of care for most diabetic patients with
multivessel CAD,the paradigm may begin to shift.Further follow-up from the initial stent
versus CABG studies will offer insight;however,the field has already begun to move beyond
these trials.Data from randomized controlled trials comparing DES with CABG in patients
with diabetes,such as FREEDOM ,CARDia and ARTS II –may help clarify this issue.
Additionally,greater and more sustained use of both intravenous and oral antiplatelet agents,
and the use of hybrid operative and PCI procedures will also change practice patterns in the
coming years.

In conclusion,all patients should be reviewed and discussed by a team of both a cardiac
surgeon and an interventional cardiologist to reach a consensus on optimum treatment.
Treatment advice for an individual patient should take into account patient preferences,as well
as the risks and benefits of the respective treatment options.However,the delimma remains:
PCI vs CABG?

 

DR SOHAIL KHAN BANGASH
Assisstant Professor
Deparment of Pediatric Cardiac Surgery
NICVD,Karachi.

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