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Coronary Artery Bypass (CABG)
WHAT IS CORONARY ARTERY BYPASS GRAFTING (CABG)?
Coronary artery bypass grafting or "CABG" (often pronounced "cabbage")
is the most commonly performed "open heart" operation in the United
States. Cardiothoracic surgeons perform the procedure to bypass blockages or
obstructions of the coronary arteries. The coronary arteries are the blood
vessels that supply the heart with oxygen and nutrients. The heart relies on
these fuels as it works constantly to pump blood through the body. The heart
never rests like the other muscles in the body, and it demands a constant supply
of fuel day and night. The term ischemic heart disease refers to this condition,
when the heart does not get these fuels. When the heart is sufficiently ischemic
(when the shortage of fuel is critical enough), the muscle begins to die. This
is a "heart attack" or myocardial infarction.
WHAT CAN HAPPEN WHEN BLOCKAGES OCCUR IN THE BLOOD VESSELS LEADING TO THE HEART?
When there are blockages of the arteries to the heart, an individual may experience
chest pain or angina pectoris, or ultimately even a heart attack or myocardial
infarction. In some cases, particularly in individuals with diabetes mellitus,
angina may be absent or infarctions "silent." A heart attack may
be the first sign of coronary artery disease in many patients, and an electrocardiogram
or EKG may be normal - even in the presence of coronary artery disease - if
you have not yet had a heart attack.
You or your doctor may be suspicious of coronary artery disease if you have
suggestive symptoms, multiple risk factors, and/or a strong family history
of coronary artery disease. Risk factors include male sex, high blood cholesterol,
diabetes mellitus, high blood pressure (hypertension), and cigarette smoking.
The presence of coronary artery disease is most often confirmed by a noninvasive
stress test or by cardiac catheterization. A stress test is performed on a
treadmill with monitoring by electrocardiogram or echocardiography. It can
often be performed as an outpatient. A cardiac catheterization study is an
invasive test in which a small tube or catheter is passed through the artery
in the groin or arm to the heart, and contrast medium or "dye" is
injected into the coronary arteries. X-ray pictures are taken which can show
the obstructions present.
Once coronary artery disease is diagnosed, there are a number of treatment
options including medicines, angioplasty, and surgery.
WHAT ARE THE INDICATIONS FOR SURGERY?
The indications for CABG were first defined by the results of the Coronary
Artery Surgery Study or CASS. The study was performed by cardiothoracic surgeons
and cardiologists in the early days of bypass surgery. It showed a survival
advantage for patients undergoing surgery who had disease of the left main
coronary artery and those with disease of all three major coronary arteries
and abnormal function of the main pumping chamber of the heart, the left ventricle.
CABG may also be indicated in other specific circumstances, or when an individual
patient is experiencing severe angina pectoris that cannot be controlled with
medicines alone. The most important thing to keep in mind is that coronary
artery disease is complex and every patient's specific situation is different.
You should therefore discuss your circumstances with your doctor.
HOW IS THIS OPERATION PERFORMED?
Coronary Artery Bypass Grafting is a procedure performed exclusively by cardiothoracic
surgeons. The traditional technique involves an incision down the front of
the chest through the breastbone or sternum. This incision is called a median
sternotomy. Through this incision the surgeon can see the heart and the aorta.
The procedure as traditionally performed requires that the patient be connected
to the heart lung machine while the bypasses are being performed. The heart
can then be stopped using a special mixture of chemicals called cardioplegia.
After the bypasses have been performed the patient is taken off of the machine
and their own heart takes over once again.
All bypasses were originally performed using saphenous vein from the leg to
carry blood around the obstruction. The vein was attached at one end to the
aorta and at the other end to the coronary artery beyond the blockage.The surgeon
connects the vein to the aorta and to the coronary artery.
In the 1970's and 1980's, cardiothoracic surgeons discovered that an artery
from the inside of the chest wall, the internal thoracic artery (also called
the internal mammary artery), could be used instead of vein for the bypass
grafts and that it stayed open longer than saphenous vein grafts. Today most
CABG operations are performed using a combination of bypass grafts including
this artery and some saphenous vein. This illustration shows a heart with the
left internal thoracic artery grafted to the anterior descending coronary artery
.
WHAT NEW PROCEDURES ARE BEING PERFORMED NOW?
Newer techniques are being explored to improve the results and to minimize
the discomfort patients feel during recovery from CABG. One technique to improve
patient outcomes involves the use of multiple arterial grafts - doing all bypasses
with arteries like the internal thoracic artery - and not using the saphenous
vein. Because of the positive experience with internal thoracic arteries staying
open longer than veins, cardiothoracic surgeons are trying to do all of the
bypasses with arteries with the aim of reducing the patient's risk of needing
another operation.
Another technique aimed at improving outcomes for the patient is performing
the bypass operation without using the heart lung machine at all. During the
procedure the heart continues to do the work of pumping blood to the body while
surgeons perform the bypass operations on the beating heart. Other techniques
in development involve the use of smaller incisions to perform CABG. All of
these techniques are commonly referred to as "minimally invasive heart
surgery." In all cases the hope is that patients will have less pain and
a faster recovery and return to work.
ARE THERE ANY RISKS OR POTENTIAL COMPLICATIONS TO CONSIDER PRIOR TO CABG?
WHAT ARE THE RISKS OF SURGERY?
Surgery is not an option to be considered lightly. Your cardiologist and cardiothoracic
surgeon will only recommend CABG when they believe other options like prescription
drugs or balloon angioplasty cannot achieve the goal of keeping a patient healthy.
As with any other surgical procedure, there are certain risks that a patient
should be aware of prior to surgery. The magnitude of risks vary according
to each patient's specific health conditions. Potential complications of CABG
include bleeding or infection, stroke (which is primarily related to age and
history of previous stroke), kidney failure (related in large measure to the
kidney function before the surgery), and heart attack during or after the surgery.
Please keep in mind that estimates of a particular patient's risk of any of
these complications can only be made by the physician taking the individual
patient's specific health circumstances into consideration. The risk of complications
generally depends upon age, general health, smoking history, specific medical
conditions, and heart function.
WHAT ARE THE CHANCES FOR LONG-TERM SUCCESS AFTER CABG?
The long term results of CABG are excellent. The majority of patients obtain
excellent relief of their symptoms of angina after surgery. Some patients notice
an increase in their energy level after recovery -- and will state that they
had not realized how much they had been slowing down prior to surgery. Although
symptoms may recur, most patients have sustained relief. A minority of patients
will require repeat surgery , usually 10 or more years after their original
operation. Because of a number of improvements in the procedure, most cardiothoracic
surgeons feel that fewer and fewer patients will need reintervention in the
future. In addition to the relief of symptoms, research shows that the expected
survival (life-span) for specific subgroups of patients improves after CABG.
ARE THERE ANY ALTERNATIVES TO CABG?
Alternatives to surgery include aggressive medical therapy and balloon angioplasty
for suitable candidates. Significant advances are constantly being made on
both of these fronts. Patients and their families should ask their cardiologist
or cardiothoracic surgeon about alternatives to surgery.
WHAT WILL A PATIENT'S MEDICAL CONDITION BE LIKE AFTER CORONARY
ARTERY BYPASS GRAFTING?
After successful CABG, a patient's anginal chest pain should resolve, although
they will likely experience some incisional chest discomfort. Surprisingly,
however, even the incision does not bother most people much after the first
48 to 72 hours. Some patients find that their energy level actually improves
after surgery. Early on, however, a patient will likely feel "washed out" or "drained" while
their body recovers from the trauma of surgery.
In the long run a patient can expect to return to their preoperative condition
or better.
Thoralf Sundt for Society of Thoracic Surgeons (2000)
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