Download Abstract

Is Coronary Artery Bypass
Graft Really Better Than
Coronary Stents?
(A look at the risks and benefits of both)
Sarah Smith
February 29, 2007
PAS 646
Advisor: Dr. Grimes
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ABSTRACT:
Coronary heart disease is the leading cause of death in the United States for both men and
women. Coronary artery disease approximately accounts for 43% of these deaths, and by
2020 it will become the world’s most prevalent cause of death and disability. There are
multiple treatment procedures that are used to relieve the symptoms and provide a route
for blood to flow unobstructed. Coronary artery bypass surgery (CABG) and
percutaneous coronary intervention (PCI) with stents are the procedures that are focused
in this review. The purpose of this paper is to review current literature, in affect to
analyze the benefits and risks of coronary artery bypass surgery and percutaneous
intervention with the use of bare-metal stents and drug-eluting stents. Current studies
have confirmed that CABG is still the best technique for patients that have proximal left
anterior descending, multivessel, and left-main stem coronary artery disease. CABG has
also shown that its effectiveness is magnified in patients who are diabetic. PCI has
undergone tremendous growth over the past decades with the numerous technological
advances. It has evolved from its initial use of balloon angioplasty techniques to use of
bare-metal stents and, more recently, drug-eluting stents. PCI with stents was found to be
effective in patients that have single-vessel coronary disease, because of its lower clinical
risk and reduces angina and myocardial ischemia in patients. The ratio of PCI to CABG
use exceeds 4:1. This review analyzes the limitations of both procedures and analyzes the
most appropriate procedure for certain types of vessel disease.
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INTRODUCTION:
The leading cause of death in the United States is coronary heart disease
(Mercado, 2005). Approximately 43% of coronary heart disease deaths are related to
coronary artery disease (Mercado, 2005). Coronary artery disease has become the most
important cause of death and disability particularly in developed world; approximately
60% of them have multivessel coronary disease that is usually treated with either
percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG)
surgery (Mercado, 2005). There has been a large controversy over the preferred method
of treatment of multivessel disease. Many studies and clinical trials have suggested
higher restenosis and repeat revascularization rates in patients who were treated with bare
metal stents rather than those with surgery. There have been great advances in
techniques and devices used including the advancement of drug-eluting stents. Drugeluting stents have been shown to be much more successful with lower repeat
revascularization rates, suggesting that PCI with drug-eluting stents should be considered
for the preferred strategy. CABG surgery has been the main surgery used for many years
to treat coronary artery disease. I would like to compare the outcomes of both techniques
and explore the benefits and risks associated with them. Heart disease is something that
affects almost every family and both of these techniques are relatively common and most
of the students have probably heard of them or had a family member that has had to go
through one of these surgeries. I found this topic interesting because I think the heart and
cardiac system is fascinating. Prior to entering PA school I shadowed a PA in multiple
CABG surgeries. I thought that this surgery was amazing and wanted to get a little more
information about the disease and the techniques commonly used in hospitals. I would
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like to find out if there is an increased prevalence of repeat revascularization in one or
both of these. I would also like to find out the mortality rates after the procedures. I
think that CABG surgery has a higher mortality rate during surgery, but possibly a better
outcome long-term. I also think that in the patients who receive a stent they will have a
higher incidence of repeat revascularization that with CABG. I think that this topic will
be very interesting and will hopefully spark some interest in my fellow classmates.
EPIDEMIOLOGY and PATHOPHYSIOLOGY:
Coronary artery disease (CAD) occurs when atherosclerotic plaque builds up in
the wall of the arteries that supply the heart. Basically, CAD is a disease caused by
“hardening” of the coronary arteries on the surface of the heart (Michaels, 2002). After
decades of progression, some of these atheromatous plaques may rupture and start
limiting blood flow to the heart muscle. This disease is the most common cause of
sudden death and is also the most common reason for death of men and women over the
age of 20 years of age. Most recent trends in the United States suggest that half of healthy
40-year-old males will develop CAD in the future, and one in three healthy 40-year-old
women (Michaels, 2002).
CAD is a chronic process that begins in adolescence and will progress slowly
throughout life. Risk factors include family history of premature CAD, smoking,
diabetes mellitus, hypertension, hyperlipidemia, a sedentary lifestyle, and obesity. These
risk factors accelerate or modify the process that produces atherosclerotic plaques.
Atherosclerosis is the most common cause of CAD, and plaque rupture is the
most frequent cause of myocardial infarction and sudden cardiac death. Atherosclerosis
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can affect one or all three of the major coronary arteries and their branches, but most
commonly in the left anterior descending and left circumflex or right coronary artery.
The first step in the atherosclerotic process is the development of fatty streaks.
These streaks form between the endothelium and the internal elastic lamnia (Libby,
2005). Overtime a fibrous cap forms and will play a critical role in the development of
acute coronary syndromes. Fixed or stable plaque obstructs blood flow. Stable plaques
develop over several decades until they may cause stenosis or occlusion. Unstable or
vulnerable plaque can rupture and cause platelet adhesion and thrombus formation.
CAD can be thought of as a wide spectrum of disease of the heart. At one end is
the asymptomatic individual with fatty streaks within the walls of the coronary arteries.
Over a long period of time, these streaks or atherosclerotic plaques will increase in
thickness and may affect the flow of blood through the arteries. As the plaques continue
to grow and obstruct the vessel to more than 70% the patient typically develops
symptoms of obstructive coronary artery disease. At this stage the patient is said to have
ischemic heart disease, meaning that the patient’s heart is experiencing an increased
workload and means that there is reduced blood supply to the heart.
Ischemia means that the supplied oxygen to the tissue is not enough, thus impairs
the function of the heart. When large areas become ischemic there can impairment in the
contraction and relaxation of the heart. If the blood flow is improved then myocardial
ischemia can be reversed, which is unlike an infarction. Infarction means that the tissue
has undergone irreversible death of tissue due to lack of oxygen-rich blood. The first
symptoms typically seen are angina or decreased exercise tolerance. As the degree of
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obstruction progresses there can be complete obstruction of the coronary artery, severely
restricting the amount of oxygen transported to the myocardium.
Patients present with stable angina, unstable angina pectoris, or a myocardial
infarction, acute coronary symptoms. Patients may seek first medical treatment when
they experience chest discomfort. The diagnostic approach should include a detailed
patient history, a complete physical exam, and an electrocardiogram. It is important to
evaluate the patient’s blood pressure and ankle-brachial index and screening for
hyperlipidemia and diabetes mellitus. During cardiac auscultation murmurs may be
detected due to aortic stenosis or hypertrophic cardiomyopathy. Electrocardiographic
results are normal in about 50% of patients with chronic stable angina, therefore a normal
EKG does not exclude coronary artery disease (Michaels, 2002). Some things to look for
on the EKG are presence of left ventricular hypertrophy, ST-segment changes, T-wave
changes, and conduction abnormalities such as left bundle branch block. The appearance
of diagnostic Q waves in two continuous leads greatly increases the probability of CAD
(Libby, 2005).
Coronary angiogram is currently the golden standard for determining the presence
of obstructive coronary artery disease. This procedure yields a two-dimensional picture
of the coronary arteries. A catheter is inserted into the coronary arteries and the injection
of a dye allows a physician to pinpoint the number and location of blockages in the
coronary arteries. After the physician performs this there are many different treatment
options that may be taken, including possibly PCI with stent placement or bypass
surgery.
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Here are some key definitions that are used through out this paper and helpful in
understanding the disease. A single-vessel disease is defined as the presence of greater
than 50% diameter lumen narrowing in the LAD, left circumflex or right coronary artery,
or a major branch of these. Double vessel disease is considered greater than 50%
diameter lumen narrowing in 2 of the 3 major branch of any of these. Triple-vessel
disease is found in all 3 vessels. Left main disease is the presence of greater than 50%
diameter lumen narrowing in the left main coronary artery.
Overview of PCI with stents:
Roughly one-third of patients with CAD will undergo coronary angioplasty with
stenting (Michaels, 2001). PCI is also known as coronary angioplasty is used to open
clogged heart arteries. Angioplasty involves temporarily inserting and expanding a tiny
balloon at the site of the blockage to help widen the narrowed artery. This is usually
combined with implantation of stent in the clogged artery to help prop it open and
decrease the chance of it narrowing again or restenosis. PCIs are performed in the cardiac
catheterization lab and are a non-surgical treatment. This procedure usually lasts about
one to two hours and most patients are usually discharged in one or two days after a
successful procedure. Stents are a stainless steel or nytinol mesh like device that are
placed into the coronary artery on a catheter during the procedure.
Overview of Coronary Artery Bypass Grafting
In recent studies coronary artery bypass grafting (CABG) is still the best therapy
for reintervention for most patients with proximal left anterior descending, multivessel,
and left main-stem coronary artery disease, in terms of improved survival (Taggart,
2007). Of the patients with CAD, about 10% will undergo CABG surgery (Michaels,
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2001). CABG is a surgery that increases blood flow to the heart by creating a detour and
re-routing the blood flow around the blocked portion of the artery. A section of a blood
vessel from another part of the body is removed and grafted above and below the
damaged portion of the coronary artery to form an un-blocked artery. The most common
vessels used are the saphenous vein and the internal thoracic artery. Typically this
procedure is performed with assistance of a heart-lung machine, which supports the
patient’s blood while the surgeon operates on the heart. Minimally invasive bypass
surgery is a less traumatic form that relies on smaller incisions to gain access to the chest
cavity. This is a navel procedure with not many clinical trials or evidence of its
effectiveness.
REVIEW OF LITERATURE:
Comparative Effectiveness of PCI and CABG
The two procedures that are generally used as treatment options for blocked
coronary arties are PCI with stents and CABG surgery. A physician will look into the
patients’ individual risk factors, severity of the blocked artery, and analyze the benefits
and risks of both procedures. These two procedures are different in their techniques and
indications. PCI has been proven to have shorter procedural and recovery time with not
many adverse affects after the procedure. The main limitation is the incidence of
restenosis and the need for revascularization. CABG surgery has shown many benefits
such as decrease in angina, improved life-span, and providing an effective route for blood
with prevention of new plaques to form. Surgery is however a much more serious
operation that lasts a long time and has a longer recovery time. Some complications that
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are seen after surgery include atrial fibrillation, increased risk of stroke, and cognitive
dysfunction.
In 2005, 261,000 CABG procedures and 645,000 PCI procedures were performed
in the United States alone (Bravata, 2007). In patients with left main or triple-vessel
coronary artery disease, CABG has been the preferred method because it improves
survival. In patients with most forms of single-vessel disease, PCI has been shown to be
the preferred form of coronary revascularization. The risk of emergency referral for
CABG and the need for subsequent revascularization procedures has reduced by more
than 50% because of coronary stents (Villareal, 2002). Coronary restenosis has been
considered the main limitation hampering the usefulness of percutaneous
revascularization. Stent implantation has been shown to reduce restenosis in vessels with
reference diameter >3.0 mm, however in-stent restenosis still occurs in about 10-40% of
patients (Lemos, 2007). According to the 2005 guidelines issued by the American Heart
Association and American College of Cardiology, stents can be considered for use in
patients who have significant disease of left main and left anterior descending coronary
arteries. Also, stents should be three or two-vessel diseases are also possible candidates.
In previous years these patients were only candidates for bypass graft surgery.
In an interesting study (Bravata, 2007), compared the long-term outcomes of both
procedures. The study found that procedural survival was high for both procedures:
98.9% for PCI and 98.2% for CABG. Angina relief was more common after CABG than
with PCI at 1, 3, and 5 years after the procedure. Patients who received PCI didn’t have
angina 75% of the time compared to patients receiving CABG 84% of the time. This
study also discovered that there was a great proportion of patients who underwent CABG
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surgery were without repeated coronary revascularization (96.2% at 1 year and 90.2% at
5 years) compared with PCI (73.5% at 1 year and 53.9% at 5 years).
In another study (Mercado, 2005), patients who received PCI with stents had a
significantly lower incidence of death, MI, or stroke at 30-day follow-up to CABG
surgery. However, patients receiving stents had a higher incidence of repeat
revascularization procedures at 30 days. At a 1-year follow up the incidence of death,
MI, or stroke where similar between the two procedures; 8.7% after stents and 9.1% after
CABG surgery.
This study supports the main limitation of bare-metal stents that most other
studies have found as well, that there is an increased rate of restenosis among patients
who receive stents. The main complication of untreated restenosis is refractory angina
pectoris (Lemos, 2003). The anticipated high risk of in-stent restenosis is one of the
major reasons for patients refusing angioplasty and opting for other treatment modalities.
The introduction of drug-eluting stents may hopefully shift patients from surgical
procedures toward PCI. Long-term follow-up in patients with bare metal stents shows
that tissue proliferation reaches its peak at around 6-12 months and then regresses
(Daeman, 2007).
In recent years, drug-eluting stents have become a pharmacologic advance that
has aided in the reduction of re-stenosis which happens with the bare-metal stents. These
stents are a normal metal stent that has been coated with a drug that is known to interfere
with the process of restenosis. As of December 2007, the FDA has approved two drugeluting stents: sirolimus-eluting stents and paclitaxel-eluting stents.
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In a recent study (Kaiser, 2005), it states that there is an overall 44% reduction
rate of major adverse cardiac events with drug-eluting stents compared with bare-metal
stents. This study suggests that possibly drug-eluting stents could be restricted to certain
high-risk patients subgroups such as high-risk elderly patients with three-vessel disease,
treatment of multiple segments.
There are a couple of problems with the drug-eluting stents however. One
problem is that the agents loaded on the stents can interfere with the healing process. On
detailed examination of the area where stent was introduced there was adhered platelets
and inflammatory cells, and absent endothelium for prolonged periords ( Morton, 2007).
Second, in a study (Daemen, 2007), found the drug-eluting stents proved to hamper the
natural vascular healing process. Third, the drug-eluting stents are still being debated as
to their cost-effectiveness.
Even higher rates of reduced rates of restenosis by 70%-90% compared with
conventional bare-metal stents in a recent study (Ryan, 2006). The drug-eluting stent
were first introduced in April, 2003, and just 9 months later they made up 35% of all
stent implantation in the United States (Ryan, 2006). This study also analyzed the costeffectiveness of drug-eluting stents. It was determined that many US centers pay roughly
$2200 per drug-eluting stent, when compared with an average $600 per bare metal stent.
Since most procedures require more than one stent, the price per procedure is actually an
increase of $2500. This higher upfront increase may offset the reduced repeat
revascularization procedures. This study determined that there was still an increase of
$600 per PCI patient, and with an estimate of 1 million PCI procedures per year that is
about $600 million in increased annual healthcare spending. This increase in cost on the
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health care system could cause a dilemma on the economic perspective of the US
healthcare system and in this study it is suggested that drug-eluting stents might bankrupt
the system
Another study also analyzed the cost effectiveness of drug-eluting stents, since the
stents are much more expensive than bare metal stents (Kaiser, 2005). In a study
(Lemos, 2003), suggested that there is a potential $2000 difference between drug-eluting
stents and bare stents, which if every person that went under PCI received a drug-eluted
stent would be an extra $2.4 billion difference in costs per year. Drug-eluting stents
reduce the risk of restenosis in low-risk coronary lesions, but do not reduce the risk of
mortality or subsequent myocardial infarction. In an interesting study (Farb, 2007),
suggested that stent thrombosis appears to be potentially important limitation of drugeluting stents associated with an increased risk of myocardial infarction of 65-70% and of
mortality of 25-45%. While the precise incidence of stent thrombosis with drug-eluting
stents is unknown, the FDA has cautioned that the use of drug-eluting stents is associated
with increased risks of both early and late stent thrombosis, as well as death and
myocardial infarction (Farb, 2007). It will be interesting to see the continued clinical
trials on drug-eluting stents to see how effective they are and what future indications they
could be used for.
Implantation of bare metal stents have showed to be effective for single vessel
disease, however there are limitations First, stents cause permanent physical irritation
with the risk of long-term endothelial dysfunction or inflammation (Virmani, 1999).
Second, stents pose a high thrombogenicity (Tepe, 2002). Third, stents create an inability
for the vessel to remodel and act in a normal physiological way (Hofma, 2006). Fourth,
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stents create difficulties for possible future bypass surgery and noninvasive imaging.
Finally, probably the biggest limitation is revascularization with bare metal stents, as
mentioned prior.
CABG surgery was introduced approximately 50 years ago and is now performed
in 1 million patients at a cost exceeding $20 billion annually (Ott, 2007). The long term
results of CABG surgery are generally positive and include relief of symptoms of angina,
improvement in energy levels after recovery, and improved expected life-span for
specific subgroups of patients. Angina relief is more common after CABG than after PCI.
At a 1 year proportion of patients without angina was 75% in PCI patients compared with
84% in patients who underwent CABG surgery. CABG is superior to PCI in mutivessel
CAD in terms of death, myocardial infarction, and repeat revascularization regardless of
stent type (Yang, 2007). CABG is the preferred treatment for disease of left main
coronary artery and three-vessel disease. CABG is generally the preferred treatment with
other high-risk patients such as those with sever ventricular dysfunction or diabetes
mellitus.
Some limitations of bypass surgery have been discovered. Bypass surgery carries
some risks, including a less than 5% chance of heart damage and less than 2% chance of
death (Stephenson, 2004). Cognitive dysfunction is reported in 53% of CABG surgery
patients at discharge, 36% at six weeks, and 42% at five years (Harmon, 2004). It has
also been found that stroke or neurological injury occurs in 5% of patients undergoing
CABG surgery (Medline Plus). Blood platelet transfusions during CABG surgery have
been association with a three-fold increased risk of stroke and five-fold increased risk of
death (Spiess, 2004). Some other complications associated with CABG surgery include
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bleeding, infection, difficulty breathing, hypertension, abnormal heart rhythm;
particularly atrial fibrillation. All of these risks are higher for older patients, diabetics,
patients with other major health problems and those undergoing a repeat bypass
procedure (Stephenson, 2004)
Atrial fibrillation occurs in 20%-40% of patients after CABG (Zaman, 2000).
One study (Zaman, 2000) discovered that 28.2% of the patients developed atrial
fibrillation. They discovered a couple of risk factors that might contribute to this risk
factor associated with CABG surgery. Advanced age was strongly associated with
postoperative atrial fibrillation. The mean age in this study was 65.9 in the atrial
fibrillation group compared with 61.7 years in the non-atrial fibrillation group. There
was an increased incidence of atrial fibrillation in patients aged 70-74, 42.2% chance of
developing atrial fibrillation. It is important for a patient and their doctor to look into
their risk factors and helping to identify the vulnerable patients for atrial fibrillation.
There are two reasons as to why CABG offers survival advantages for multivessel
and left main-stem coronary artery disease. First, since bypass grafts are placed on the
midcoronary vessel, CABG does not only protect whole zones of vulnerable proximal
myocardium against the culprit lesion, but it also offers prophylaxis against new lesions
in diseased endothelium (Taggart, 2007). PCI in contrast, only treats the immediate
culprit lesion, but has no protective effect against the development of new proximal
disease. Second, the failure of stenting to achieve complete revascularization in most
patients with multivessel disease reduces survival proportional to the degree of
incomplete revascularization (Taggart, 2007).
Isolated LAD and Left main-stem coronary artery disease
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Coronary artery disease involving the left anterior descending artery (LAD)
incidence has been reported as high as 50% among patients who undergo CABG (Aziz,
2007). The LAD coronary artery supplies the vast majority of the myocardium. LAD
artery arises off a branch of the left coronary artery. The left anterior descending artery
usually follows the anterior interventricular groove and in some people continues over the
apex. This artery supplies the anterior septum and anterior wall of the left ventricle. It
has been discovered that patients with significant LAD disease, particularly when the
proximal part is affected, have adverse prognosis compared with patients who do not
have LAD involved (Okeefe, 1999). CABG is regarded as an accepted golden standard
for left main coronary artery disease (Gupta, 2007).
There are numerous articles that suggest similar results as stated above. In a
meta-analysis (Rao, 2007), it was found that initially PCI with stents are cheaper and
more effective than bypass surgery, but surgery is more cost effective long term. It was
found that the overall cost for stenting was $12508 per patient and bypass cost about
$14459 per
patient. In this same study it demonstrated that an internal mammary artery
graft to the LAD artery by a minimally invasive approach is both clinically and
economically more effective than stenting with bare metal stents over a 4-year period.
PCI resulted in a three-fold increase (13%) in recurrent angina and the need for
reintervention in comparison with surgery (4%) (Aziz, 2007).
In another study (O’Keefe, 1999), it was discovered that using stent or CABG
resulted in low in-hospital morbidity and mortality rates and good immediate-term
results. They also discovered that with stents repeat revascularization was required
significantly more often (O’Keefe, 1999). In patients that received stents at a 6-month
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follow-up had superior exercise tolerance and improved anginal status, but is limited to
frequency of restenosis. In the patients that underwent CABG the mean length of stay
was 5 days after surgery, versus only 1 day for stent patients.
Patients with isolated left main coronary artery disease should be considered for
CABG. Left-main stem stenosis is reported to be present in 4-6% of patients undergoing
coronary angiography (Taggart, 2007). CABG has generally been considered the golden
standard of therapy for left main-stem stenosis for the last decade. However, there are
recent studies out that show patients underwent PCI more than CABG for this type of
disease. This artery has a relatively large diameter, making it an attractive site for PCI.
In a recent study (Serruys, 2005), it was discovered that the restenosis rates were
30.3% in bare-metal stent group, 7.4% in drug-eluting stent group, and 3.7% in CABG
group. It was argued that the drug-eluting stent group might save the patients from fear
and pain of surgery while giving equal benefits of survival and reduced rates of restenosis
and need for repeat revascularization. Another study (Lee, 2006), suggested that PCI with
drug-eluting stents can be considered reasonable if revascularization is essential to save
the life and to improve the cardiovascular outcome in patient who is not suitable for
CABG.
PCI should be considered as an alternative to CABG under the following
circumstances. First, in a patient who refuses CABG surgery. Second, in a patient that is
considered unsuitable for CABG by cardiac surgeon in view of co-morbidities or
complications. Finally, should be considered if the lesion location where stenting can be
done safely (Gupta, 2007).
Multivessel Coronary Artery Disease
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Multivessel coronary disease (MVD) accounts for approximately 60% of the
CAD patients (Yang, 2007). There are numerous studies comparing the two methods for
treatment of the MVD. Numerous studies have reported that the use of stented patients
has resulted in higher restenosis and repeat revascularization rates than in patients treated
with surgery. In one study (Serruys, 2001), patients that underwent stenting, 16.8%
compared with 3.5% that underwent surgery encountered repeated revascularization.
This study also found that there was greater angina relief with surgery than with stents
after one year. They did not find a significant difference between the rate of death,
stroke, and myocardial infarction. The use of stents however is less expensive than
surgery. The total cost of bypass surgery was estimated at $10,653 as compared to
stenting at $6,441. The difference in cost is primarily due to the length of stay in the
hospital and the duration of the procedure.
In an interesting study (Bair, 2005) that followed the long-term outcomes between
the two identified a significant difference. This observational study of patients with
MVD, followed patients for more than 5 years of follow-up discovered that CABG was
found to have a significant survival advantage over patients undergoing PCI with stents.
The CABG patients also experienced fewer repeat revascularization and MI and 43%
fewer events for the composite end point of major adverse cardiovascular events.
The development of drug-eluting stents has decreased the difference between
CABG and bare-metal stents. As mentioned earlier drug-eluting stents reduce the
restenosis percentage and thus many clinical trials have been conducted in order to
consider PCI with drug-eluting stents as the treatment for MVD. In one study (Yang,
2007), there was significantly higher in-hospital morbidity associated with bypass
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surgery (3.9% vs. 0.8%). There were similar percentages in the incidence of death,
myocardial infarction, and cerebrovascular events in the two groups. Finally, the
incidence of major adverse cardiovascular events was still higher in the PCI group in the
long-term follow-up (14.5% vs. 7.9%). This difference was mainly driven by the repeat
revascularization after PCI.
In another study (Javaid, 2007) similar results found CABG resulted in improved
major adverse cardiovascular and cerebrovascular event in patients with 2 and 3 vessel
disease. In order for PCI to replace CABG as the preferred therapy in MVD clinical trials
must demonstrate that long-term outcomes are at least equivalent. There are currently a
couple of clinical trials studying the long-term effects of drug-eluting stents and CABG,
but have not finished yet.
The Diabetic Patient
The diabetic patient is at a high risk for coronary artery disease. The incidence, as
well as severity of the disease, has been shown to be highly increased in comparison to
the nondiabetic patient (Elsasser, 2006). These patients are at an increased rate for shortand long-term mortality as well as higher risk of revascularization procedures. The
revascularization of these patients has been a huge dilemma and a great challenge. A
study (BARI Investigators, 2007), confirmed that even in relatively low-risk diabetic
patients there is a survival advantage at 10 years for CABG in comparison with PCI of
58% vs. 46%. This study also concluded that there was a large difference in the need for
reintervention in both of these; 18% of CABG patients versus 80% of PCI patients.
These results are also consistent with a 5-year survival data finding that CABG was 92%
survival vs. 87% for PCI (Serruys, 2005). This study also found that the need for
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reintervention was much higher with PCI than with CABG; 10% of CABG patient and
43% of PCI patients.
Another study suggests that CABG surgery may be the preferred revascularization
strategy in the diabetic patient with MVD. In the study (Javaid, 2007) the incidence of
MI was similar between the two groups of patients. The patients who underwent CABG
showed reduced mortality; 1.4% for CABG patients and 12.8% for PCI patients. Also,
this showed a reduced rate of major adverse cardiovascular events; 8.6% for CABG
patients and 26.6% for PCI patients. These results support the theory that in the diabetic
patient CABG surgery benefits are magnified when compared to PCI and possibly is the
preferred method for these difficult patients
The Future
In recent years, minimally invasive direct coronary artery bypass (MIDCAB) has
been used for treating patients with proximal stenosis of LAD (Jaffery, 2007). It is
performed on a beating heart with use of stabilizing devices or using minimal access
bypass system with endo-aortic clamping and cardioplegic arrest. This procedure enables
a shorter hospital stay with lower postoperative complications and better quality of life
with similar safety and long-term efficacy as conventional CABG (Jaffery, 2007). There
are a couple of studies that are compared to PCI. In a study (Aziz, 2007) PCI resulted in
a three-fold increase in recurrent angina and the need for reintervention than with
MIDCAB. This new technique has only started to take some ground in the strategy for
treating CAD, it will be interesting to see what future clinical trials come out and what
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finding may be made. Maybe this new technique will help propel surgery back into the
treatment of not only MVD and LAD artery disease.
A minimally invasive surgery also has developed into the use of wrist-enhanced
robotic instrumentation. It is leading to a turning point in the history of MICS (Kappert,
2006). The first patient to receive robotically-assisted coronary artery bypass surgery
was in 2002. This surgery does not have a single chest incision of any kind. This surgery
requires only three pencil-sized holes made between the ribs. Through these holes, two
robotic arms and an endoscope gain access to the heart, making surgery possible without
opening the chest. It has been proven that these patients get out of the hospital one to two
days earlier than open-heart surgery. There are several centers that are currently using
surgical robots and the use of them is still in its youth and studies still need to be done to
understand it better. This technique might as well be a new technology that might be
used more often in the future and maybe even replace bypass surgery.
CONCLUSION:
Current studies have reconfirmed that CABG remains the best therapy in terms of
superior survival and decreased need for reintervention for most patients with proximal
left anterior descending, multivessel, and left main-stem coronary artery disease. These
affects are magnified in the diabetic patients. PCI is still chosen as the treatment option
for single-vessel disease. Coronary stents treat diseased arteries with fewer trauma on the
patient than with bypass surgery. Stents have proven to reduce chest pain, lower risk of
heart attack after the procedure, and decreased hospital and procedural time. The only
limitation that has been a problem is restenosis of the artery and the need for
revascularization.
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As technology continues to advance, stents are becoming superiof for patients
with more complex disease, therefore reducing the number of surgeries. With the
evolution of drug-eluting stents and minimally invasive surgeries with assist of robots the
current guidelines may change. It will be interesting to see where revascularization will
be in the next five years.
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REFERENCES:
Anderson, H. Vernon, Richard E. Shaw, Ralph G Brindis, Kathleen Hewitt, Ronald
Krone, Peter C. Block, Charles R. McKay, Williams S. Weintraub. “A
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