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| Dr Gershlick trained in
cardiology in London and
moved to the University of
Leicester in 1990 to take up
a formal Senior Lecturer's
post, transferring to the
NHS in 1993. However, he
has maintained a significant
research interest, publishing
extensively in the area of
vessel wall/blood interactions
especially those that occur
following percutaneous
coronary intervention.
Research has included basic
laboratory work involving
drug-eluting stents, and
he has also been principal
investigator in a number of
national and international
studies. Dr Gershlick is
currently involved in studies
of myoblast injection and
bone marrow cells for patients
with failed lysis and impaired
left ventricular function. He
is a council member of
the British Cardiac Society,
Scientific Officer of the British
Cardiovascular Intervention
Society and Chairman of
the local Cardiovascular
Programme Board. |
Left main stem stenting
Anthony H Gershlick
University Hospitals of Leicester
Address for correspondence:
Dr Anthony H Gershlick
Consultant Cardiologist
Clinical Sciences Department, Glenfield Hospital
Groby Road, Leicester, LE3 9QP, UK
Tel: +44-(0)116-256-3887 Fax: +44-(0)116-287-5792
Email: agershlick@aol.com
Unprotected stenosis of the left main coronary artery greater than 50% has traditionally been managed
with coronary artery bypass surgery (CABG). There is now emerging evidence to support the use of
percutaneous coronary intervention (PCI) with drug-eluting stents, especially in patients at high risk for
surgery. However, the widespread use of PCI instead of CABG remains very controversial.
In this issue, an interventional cardiologist discusses this question and presents his own perspective on
the appropriate selection of therapeutic strategy. The available evidence is reviewed and summarized and
some of the unanswered questions are highlighted. Several large clinical trials comparing percutaneous to
surgical intervention are currently in progress and the results of these will help clarify the situation.
In the next issue, the question will be viewed from the perspective of a cardiac surgeon. |
Abstract
Percutaneous treatment of obstructive coronary
disease has, for a number of years, been undertaken
more commonly than the coronary artery bypass graft
(CABG). Technical developments, operator skill and the
advent of drug-eluting stents has meant that most
lesions can be treated effectively with little associated
morbidity and with rapid patient discharge. When
considering more complex disease two issues need to
be considered:
-
Can it be technically undertaken safely
with percutaneous coronary intervention (PCI)?
-
Are there data to suggest the benefit of one
revascularisation technique over another?
There are no robust data that approach the rigours of
unchallengeable evidence to support CABG over PCI.
The only randomised study comparing the two will be
published in 2008. In the meantime, each case should
be viewed individually patients with co-morbidity
or with lesions in the ostium or the body should be
seriously considered for PCI. Those with bifurcation
disease might, because of the increased technical
aspects of PCI in such cases, be considered for CABG.
Introduction
Percutaneous coronary angioplasty is now the
dominant therapy for treating symptomatic
obstructive coronary disease. It has progressed from
being a therapy tailored towards straightforward
simple lesions to encompassing complex disease
previously considered suitable for coronary artery
bypass graft (CABG) surgery only. This article will explore the devolution of percutaneous coronary
intervention (PCI) into previously surgical disease,
address the data available and indicate best
contemporary practice.
The evolution of PCI
Percutaneous coronary angioplasty has undergone
considerable development and overcome many
inherent problems since it was first introduced by
Andreas Gruntzig in 1977. The 1980s saw a rapid
expansion in PCI with crossover in numerical terms
from CABG to angioplasty occurring as early as 1998
in the United States. However, there were problems
that needed resolving.
The first of these was restenosis, which in the early
1990s was a catch-all term describing the pathological
changes that developed in up to 35% of patients
after balloon angioplasty, resulting in the need for a
repeat procedure. Restenosis was thought to be the
consequence of scar tissue formed through response-to-
injury mechanisms within the vessel wall which
then encroached on the lumen. A more immediate
problem was acute vessel closure. PCI causes intimal
layer disruption indeed, this is partly how balloon
angioplasty works. In the late 1980s/early 1990s,
acute closure of ballooned vessels led to many
patients needing emergency CABG surgery to prevent
myocardial infarction/death.
The development of the stent to prevent the
disrupted flap from obstructing the lumen was a
critical breakthrough. As stent use accelerated to
90% throughout the 1990s, the need for emergency surgery plummeted and is now rare (<0.5%).
Safer PCI was a major turning point in the shift
from surgery. Furthermore, it was observed that with
increased stent use the restenosis rate/need for a
repeat procedure also fell from 35% with balloon
alone to 1520% with stenting. Our understanding
of the causes of luminal re-narrowing now had to
take account of other benefits of stenting. Recurrence
was composed of 3 components: recoil of the vessel
wall, late negative re-modelling and the response-toinjury
scar. Stents clearly dealt with the recoil and the
negative re-modelling, leaving only the problematic
scar formation.
Meanwhile, it became clear that stenting carried
with it a risk of thrombus formation. Pivotal studies
comparing anti-thrombotics (e.g. coumadins) with
anti-platelet medication highlighted the value of
pre- and post-procedural dual anti-platelet therapy
(aspirin for life and thienopyridines such as clopidogrel
for one month).
A critical development in PCI was that of drug-eluting
stents (DES) that inhibit tissue growth.
Throughout the 1990s, studies were published on
the loading/elution from stents of tiny but locally
high concentrations of drugs (Ref: 1). Rapid expansion of
the concept of DES and research developments by
many groups led to pivotal clinical trials (Ref: 2-4). Use of
DES reduced clinical recurrence by 80% (from 15+%
to ~57%) especially in those patients at greatest
risk of recurrence (small vessel diameters, long lesions
and diabetics). Such indications were approved by
the National Institute for Clinical Excellence (NICE)
in 2003. Concerns regarding the small chance of
excess stent thrombosis beyond the time frame for
a bare metal stent are currently under review, with
prolonged anti-platelet therapy recommended.
Results with contemporary PCI reflect the evolution
described. The British Cardiovascular Society 2005
audit figure returns indicate procedural success rates
of 92%; Q wave MI rates of 0.3% and mortality
of 0.59%. In the UK in 2005, 28% of cases were
multivessel PCI and on average, 1.28 lesions were
treated per case. Longer-term clinical repeat
revascularisation rates for complex real world offlabel
lesions with drug-eluting stents have recently
been published at 48% (Ref: 5).
The question that is pertinent of course is how PCI and
surgery compare in studies of more complex patients and
in particular multivessel/left main stem (LMS) disease?
PCI vs. surgery in multi-vessel disease
Any reported so-called benefit for surgery in such
patients appears to be based on rather questionable
registry data. The first registry reported was that by
Hannan (Ref: 6) who compared 3-year survival outcomes
of CABG and PCI patients from two New York State
databases, and showed an apparent advantage
favouring surgery. Why only a small proportion of
patients treated in New York State during this period
(37,212 reported of 75,217 CABGs performed and
22,102 reported of 137,798 PCIs performed) were
included in this analysis is unclear. The demographic
data for the two cohorts were very different with
p values of <0.01 for most comparators, and while
these appear to disadvantage the surgical cohort,
many of the differences are small (EF 53% vs. 50%)
or would appear not to have a major impact on
mortality (peripheral vascular disease). Previous
myocardial infarction was significantly higher in
the stent group. In any event, whether any statistical
correction can take account of such differences is
questionable. The unadjusted hazard ratios show no
difference in outcome, irrespective of 2- or 3-vessel
disease or involvement of the left anterior descending
artery (LAD); the significant differences only
appeared once the ratios were adjusted to attempt
to equalise groups. Such differences in patient
cohorts make comparisons non-robust and highly
questionable.
Similar criticism can be directed towards Brener (Ref: 7)
who apparently showed a similar benefit for surgery,
this time using propensity analyses. Even the authors
acknowledge that although propensity analyses are
powerful, they are inherently limited by the number
and accuracy of the variable evaluated. There have
been substantial changes in the management of
PCI since this cohort was analysed. Since differences
between the registry populations were again so large,
one should be sceptical that any statistical test
could take account of these and the two groups
of 800 PCIs and 5000 CABGs could be considered
different non-comparable populations.
Finally, a meta-analysis by Hoffman (Ref: 8) suggests
a survival benefit favouring surgery in patients
with multivessel disease at 5 and 8 years (but no
difference at 1 and 3 years) and must be questioned.
Patency of grafts falls over time making the
contention of increased benefit of surgery over time
counter-intuitive. Worse still, 10 of the 13 trials
included in the meta-analysis were in the pre-stent
(balloon angioplasty) era.
There are data to support mortality equivalence for
PCI and CABG in multi-vessel disease. There have
been three randomised trials comparing stenting
with surgery (Ref: 9-11) which showed no mortality or acute
myocardial infarction (AMI) difference in the groups
at 1 year. The ARTS I study, which randomised
patients to bare metal stents (BMS) or CABG, has
now reported 92% survival for BMS and 92.4%
for CABG at 5.5 years (Ref: 10). These outcome data are
supported by 5-year data from the recently published
MASS II randomised trial (Ref: 11) (which showed no
significant difference in the hard endpoints of death
or AMI in the CABG and PCI groups). A meta-analysis
of all three DES trials at one year by Mercado (Ref: 12)
indicated mortality of 3% for PCI and 2.8% for CABG.
Those who say that these trials favour PCI, because
higher risk patients were excluded, should consider
the similarity in demographic and extent of disease
in both groups in these analyses. The ERACI III (Ref: 12) and
ARTS II (Ref: 13,14) DES trials show comparable mortality
and AMI rates to BMS at 12 months. All of these
data support there being no difference in mortality
between the techniques (with or without DES) in
randomised trials with up to 5-year follow-up.
Contemporary treatment of left main stem disease
The prevalence of stenosis of the left main coronary
artery at coronary angiography is approximately 5%.
There is no difference in presentation, electrocardiographic
or stress test features compared with other severe
coronary artery disease.
Current treatment considerations for left main
stem disease are also evolving and the surgery-only
paradigm has now been questioned, as PCI
has become an increasingly reliable procedure with
robust outcomes. The concept that surgery is the
only acceptable treatment for left main stem disease
is based on historical comparisons with medical
therapy. It was the CASS registry (note this was a
registry) of 1484 patients which established surgery
as the preferred treatment option (compared to
medical therapy); the 15-year survival showed a highly
significant advantage for surgery (37% vs. 27%) with
the mean surgical survival of 13.3 years vs. medical
6.6 years. Issues such as crossover and actual treatment
received are difficult to pick out from these data.
However, this set the bench mark and the standard of
care at that time and since then. It should be noted
that the results held only for those with impaired left
ventricular function; 15-year cumulative survival for
patients with normal LV systolic function in the surgical
and medical groups was 42% and 51%, respectively.
Median survival was 14.7 years in the surgical group
and >15 years in the medical group (p=NS). Those with
severely impaired LV function did badly irrespective
of surgical or medical treatment. There have been no
published randomised comparisons of surgery with PCI.
What of PCI for left main stem disease? Initial reports,
some 20 years after the first surgical reports, were in
high-risk patients with the Oxford group reporting
good outcomes in 5 elderly patients with unstable
angina and significant co-morbidities. In the late
1990s, further reports appeared of good outcomes
with bail-out stenting in patients suffering catheter-induced
trauma to the left main stem. A retrospective
registry from Marco in 2000 reported on 92 LMS
patients treated with PCI, the first 39 of which were
surgical rejects, and indicated an in-hospital mortality
of 4% and an actuarial survival of 89% at 12 months
and 85% at 36 months (Ref: 15). The ULTIMA registry of
279 patients treated with PCI for LMS disease helped
determine which patients did best with non-surgical
treatment. The overall 12-month mortality was 9%,
but when patients were divided according to risk (low
risk = <75 years of age, EF >40%, large vessels >3 mm:
high risk = older, surgical rejects, cardiogenic shock,
LMS bifurcation disease, high Euroscore) then the
outcomes were considerably different, with one-year
mortality of 3.4% for the low-risk group and 28% for
the high-risk group. The spectrum of patients treated
with PCI, including the inclusion of surgical rejects, has
led to variance in mortality after follow-up of 631
months ranging from 3.1% to 20.2% (Figure 1).
 |
| Figure 1. Mortality at follow-up in PCI series in unprotected left main stem stenosis. |
One issue has been recurrence due to restenosis.
Three series have shown improved outcome in this
context with the use of DES (Ref: 1618). While mortality
did not increase with DES, the target lesion
revascularisation rates fell from between 1720% to
26% when bare metal stents were replaced with
drug-eluting stents. However, this was not the case
for all series with one from the Italian group (Ref:16)
reporting lesser reduction in need for repeat
revascularisation.
The difference between the patients in this series
and those from Rotterdam or South Korea was the
frequency of LMS bifurcation disease, being present
in 14% of the Colombo cohort but only in 6% and
2% of the other two.
This factor becomes the linchpin of the discussion.
The outcomes with contemporary PCI for LMS disease
in lower-risk patients appear to show low mortality and low incidence of need for repeat procedure.
The issues are how good the interventionists are at
dealing with bifurcation disease (especially important
if this disease is at the end of the LMS) and what
level of risk helps determine outcome and therefore
which treatment strategy should be adopted. There
is a relationship between bifurcation and major
adverse cardiac events (MACE), which relates to the
technical aspects of treating a bifurcation. Many of
the original techniques involved the use of two stents
with various methods utilised (crush, culotte) to cover
the origin of both vessels. Increasingly, single so-called
provisional (simplified) stenting has become the
standard method of dealing with bifurcation disease
particularly following publication of the Nordic data (Ref: 19).
Such considerations are important since the mean
incidence of bifurcation disease in all LMS series is
53%, with ostial or body disease making up the rest.
In the European retrospective multicentre study of
12-month outcomes for LMS PCI (n= 300), 12-month
mortality was 4.8% irrespective of the presence of
bifurcating disease or not but the need for a repeat
procedure was 8.7% in the bifurcating cases compared
to 2.4% in the non-bifurcated cases (Figure 2).
 |
CABG Coronary artery bypass graft; MACE Major adverse cardiac events; MI Myocardial infarction; PCI Percutaneous coronary intervention;
TLR Target lesion revascularisation
Figure 2. Clinical outcomes at 1 year after stenting in cases with and without bifurcation disease. |
Hence, with simple and especially with ostial and
body lesions of the LMS, PCI outcomes appear good,
especially in lower-risk patients. In the absence of
direct surgical comparisons, what evidence do we
have concerning the outcomes with surgery and
which patients should receive which therapy? When
reported, the surgical data tend not to include the
12.8% New York State 3-year mortality or the 1374
patient Duke database of 22.6% death at 5 years.
Veldkamp reported a survival of <20% for surgically
treated LMS at 20 years (Ref: 20).
So are there any registry data comparing the two
treatments in the absence, as yet, of a randomised
trial? Certainly, the French registry comparing 192
PCI patients with 230 surgical patients shows no
difference in mortality at one year (9.4% vs. 11.6%
respectively; Figure 3), and a similar Italian registry
(Figure 4) suggests similar results in a comparison
of 107 patients treated with DES, and 139 with
CABG (84 off-pump and 55 on-pump). The mortality
rates at one year were 2.8% and 6.4% (5.9%, 7.2%)
respectively. Finally, Lee (Ref: 21) published outcomes for LMS
disease. In this series of 183 patients of whom 50 had
PCI with DES, PCI patients were required to be:
-
high risk for CABG
-
have limited life expectancy
-
unwilling to undergo CABG
-
deemed unsuitable for CABG by surgeon.
 |
CABG Coronary artery bypass graft; LM Left main; MI Myocardial infarction; PCI Percutaneous coronary intervention;
TLR Target lesion revascularisation
Figure 3. Comparison of clinical outcomes at 1 year after CABG or PCI, in the bare metal stent era (French left main registry) (Ref: 15). |
 |
CABG Coronary artery bypass graft; CVE Cardiovascular events; DES Drug-eluting stents; MI Myocardial infarction;
PCI Percutaneous coronary intervention; TLR Target lesion revascularisation; TVR Target vessel revascularisation
Figure 4. Clinical outcomes at 1 year after CABG (on or off pump) or PCI with DES (Italian registry) (Ref: 16). |
Perhaps not surprisingly, the PCI group contained
fewer men (50% vs. 76%, p<0.01), more patients
with chronic renal insufficiency (16% vs. 5%, p=0.02),
more with unstable angina (46% vs. 25%, p=0.02)
and had a higher mean Parsonnet score (18.3 vs. 13.7,
p<0.01). Despite the adverse weighting, the freedom
from MACE at one year was 82.9% for the PCI group
and 75.2% for the CABG group (Figure 5).
 |
CABG Coronary artery bypass graft; DES Drug-eluting stents; PCI Percutaneous coronary intervention
Figure 5. Survival free of MACCE (major adverse cardiac and cerebrovascular events) in patients treated with CABG or PCI with DES (Ref: 21). |
The most important study in this area, the SYNTAX
trial (n=1800), has completed recruitment. Patients
with 3-vessel disease or left main stem with or
without 3-vessel disease were randomised following
agreement between surgeons and interventionists to
either PCI strategy (using DES) or surgery. Critically,
there will be follow-up on the nested registry group of
patients deemed by consensus to be best treated by
either surgery or PCI and therefore not randomised.
Even more importantly, following the presentation of
the small LE MANS randomised trial which suggested
equivalent outcome for PCI patients and surgery
(Figure 6), the SYNTAX study was expanded to allow
sufficient power to include analysis of LMS patients alone and separately from the 3-vessel disease group.
Angiographic follow-up at 15 months in both PCI and surgical patients will provide intriguing results. To date,
the Data and Safety Monitoring Board (DSMB) have
met twice for the SYNTAX study and the trial was
allowed to randomise to completion.
 |
CABG Coronary artery bypass graft; CVA Cerebrovascular accidents; LM Left main; MACE Major adverse cardiac events; MI Myocardial infarction;
PCI Percutaneous coronary intervention
Figure 6. Clinical outcomes after PCI or CABG in the LE MANS randomized trial. |
Summary: how to decide on which therapy for
which patient presenting with LMS disease
PCI has come a long way and for most patients is
a day-case procedure with minimal morbidity and
good longer-term outcomes. Those with LMS disease
comprise a small heterogeneous but important
group for whom choice of therapy is more difficult not least being set against a background of the
standard of care historically being CABG, albeit this
has evolved from comparisons with medical therapy.
Each patient with LMS disease should be discussed at
a multidisciplinary team meeting and the following
issues taken into account. Ostial and body disease
in lower-risk patients should be considered primarily
as suitable for PCI, with any concerns over the
small and clinically insignificant excess late stent
thrombosis leading to consideration of use of BMS
in these essentially large vessels. Even so, patients
should be told that in the absence as yet of any
randomised data, the current standard of care even in
this low risk for PCI group is CABG, with the multiple
disadvantages of surgery also being highlighted. In
higher-risk patients, especially those with recognised
co-morbidity and in particular those constituting
surgical rejects (which will vary according to surgeon), the discussion requires even greater understanding
of the issues. Those with bifurcation disease, in
the absence of robust absolute understanding of
how best to guarantee PCI results, may well still be
considered to be surgical candidates. Those who will
not survive an operation but who are at risk from
their LMS disease or who have significant life-limiting
symptoms should be considered for PCI with clear
discussions with the patient and relative and clear
indication of risk in any PCI audit database. SYNTAX
may well tell us the answer as to how best treat LMS
disease but it is clear that in this context, as for other
comparisons of PCI vs. surgery, the shift is toward
PCI. When the surgeons try to attract attention, one
should consider if they are waving or drowning. From
an interventional cardiologist's point of view, PCI will
eventually replace CABG in all patients.
Study abbreviations
ARTS I Arterial Revascularization Therapy Study I
ARTS II Arterial Revascularization Therapy Study II
CASS Registry Coronary Artery Surgery Study Registry
ERACI III Trial Argentine Randomized Trial of Coronary
Stents versus Bypass Surgery Trial
LE MANS Study of Unprotected Left Main Stenting versus Bypass Surgery
MASS II Medicine, Angioplasty, or Surgery Study
SYNTAX Trial Synergy Between PCI and TAXUS and
Cardiac Surgery Trial
ULTIMA Registry Unprotected Left Main Trunk
Intervention Multicenter Assessment Registry
Key Learning
-
Dont depend on historical data
-
Dont depend on the title of any study to convince you that its contents are robust
-
Review all cases of LMS with colleagues experienced interventionists as well as surgeons
-
Discuss the real risks and outcomes with the patient and their relatives
-
Await the results of randomised controlled trials before coming to any conclusions regarding the
optimal treatment for LMS disease.
|
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