Understanding heart bypass surgery
- From: pluto <pluto@xxxxxxxxxxxx>
- Date: Sun, 12 Feb 2006 09:22:39 +0800
Sunday February 12, 2006
Understanding heart bypass surgery
BY Dr NG SWEE CHOON
CORONARY artery bypass graft surgery is commonly called CABG (pronounced
?cabbage?), or other terms like bypass and ?plumbing job?.
The terms all describe the process that takes place during the surgery.
CABG (the most common acronym) is essentially a plumbing job, done by
skilled cardiothoracic surgeons.
The accuracy of the latest cardiac scan has not been proven, but these
scans may be used to convince patients to undergo unnecessary procedures.
In CABG, the surgeon uses a vein to re-establish the blood flow caused by a
blockage in the heart artery, almost like what a plumber would do if the
kitchen sink is blocked.
Although I put this rather simply, it is actually a very complicated
surgery. This will become obvious as I go along.
Just to recall, that in 1965, Dr Mason Sones discovered the use of coronary
angiogram, a technique that allowed us to see the coronary artery in a live
person, thereby allowing us to identify blockages accurately.
Dr Sones was working in Cleveland Clinic, Ohio, in the United States. The
cardiac surgeon there at that time was a brilliant Argentinean called Rene
Favaloro.
One day, as the story goes, a young man came in with acute severe chest
pains. Dr Sones did an angiogram, which showed a right coronary artery
blockage.
As the patient was not responding well to medical therapy, Dr Sones asked
Dr Favaloro to help, using this new technique that Dr Favaloro had been
experimenting with in the animal laboratory.
The patient was an ideal candidate, and Dr Favaloro did the CABG. As they
say, the rest is history.
In the history of CABG, two earlier important advances must be recognised.
In 1950, Dr Arthur Vineberg had shown that you can cut an artery and bury
it in the heart muscle, and this can help to bring blood to the heart
muscle.
Dr Gibbons? role is also important as he invented the heart-lung machine.
To operate on the heart, you need a clean and clear surgical field, with
the heart stopped. To stop the pumping heart, the blood circulation has to
be diverted to a heart-lung machine, which will maintain the patient?s
circulation until the heart operation is completed.
After the heart operation is completed, use of the heart-lung machine is
discontinued and the patient?s own circulation is re-established.
What is CABG
CABG is an operation to treat coronary artery disease (cholesterol
blockages in heart arteries).
Imagine that the artery is like a pipe, and there is a blockage in the
pipe. The surgeon takes a vein from the leg, and introduces it across the
blockage, joining one end to the main artery of the body (aorta) and the
other end to the diseased heart artery beyond the blockage.
To allow him time to work, undisturbed by movement, the heart is stopped
and the circulation of the body is diverted to a heart-lung machine. The
machine maintains the circulation at a level adequate to sustain life.
Upon completion of the CABG, the heart is restarted, and as the patient is
slowly weaned off the heart-lung machine, the heart is allowed to take over
the circulation again.
This procedure may sound simple, but it is not. It is quite complicated and
requires a team effort (by the surgeon, the anaesthetist and the
perfusionist).
It also requires constant practice. That is why CABG success is also in
some measures dependent on the team and the number of CABG procedures they
perform weekly or monthly. Not all cardio-surgical teams have the same
success rate.
Role of coronary angiogram
The discovery of the angiogram was an important step in the development of
CABG.
It gave the cardiologists and cardiac surgeons a good look not only at the
blockage, but also at the location of the blockage, the size of the
affected artery, the area of supply of the artery, and the condition of the
artery before and after the blockage.
It also tells us the function of the heart with great accuracy. All these
details are important in deciding on CABG, its success and its risks.
Role of multi-slice CT scans
It used to be that a patient would see a cardiologist when he felt unwell
(usually from chest pains due to heart artery blockage), or as a result of
checkups that showed a lack of adequate heart circulation (from functional
testing, like stress ECG).
Then, the decision was more straightforward. Nowadays, with all the new
cardiac scan technology available and the very business-like marketing, a
completely well individual who has had a scan could end up being told that
he has blockages and that he requires immediate angioplasty or CABG.
The fact of the matter is that there are very few blockages that are silent
(not felt by the patient) and life-threatening. There have been no medical
studies to show that balloon angioplasty or CABG, when used to treat silent
blockages picked up incidentally by the latest scans, will make any
difference to the patient.
In fact, there is a lot of evidence to show that many very healthy
soldiers, killed in the Korean and Vietnam Wars, had very severe blockages
in their heart arteries. This was discovered from autopsies done on the
soldiers.
Severe blockages, when silent and not ?functionally important? (meaning
there is no evidence of functional impairment), may be compatible with
normal life.
Often, however, these blockages are presented as if every one will cause
death. This trend is very worrying as it may prompt medical practitioners
to use the ?scare of blockages? to convince patients to undergo unnecessary
procedures with the attendant risk and cost, without documented evidence of
benefit.
To date, the accuracy of the new scans has not been proven. It tends to
vary from institution to institution. What was quoted in an earlier article
(Non-invasive coronary angiogram, Fit for Life, Nov 6) was average numbers.
We are still learning how to use these scans.
Who should receive CABG?
Anyone with chest pains arising from the heart, and validated by some form
of functional cardiac testing, should have CABG.
Those without symptoms, especially those in the high cardiac risk category
(people with diabetes, those with strong family history, smokers,
hypertensives, etc), should undergo some form of functional testing, such
as stress ECG, stress echocardiogram, stress radionuclide scans etc.
Those who have the above two pre-requisites, should undergo a coronary
angiogram.
Whether or not this patient should undergo balloon angioplasty with the
drug-eluting stent, or CABG, very much depends on: a) the anatomy of the
blockages (the cardiologist?s preference); b) the resources of the patient;
and c) the patient?s preference.
This decision will require a thorough discussion of the pros and cons of
balloon angioplasty or CABG.
CABG risks
There are obviously risks with CABG.
It used to be as high as 7-10% risk of death or other complications,
including kidney failure, stroke, heart attack, heart failure, and
complications from general anaesthesia.
Nowadays, the average open-heart centre that does more then 10 bypasses a
month, should have a risk element of 1-3%.
Some risks are so slow and insidious, like long-term memory impairment,
that they are difficult to quantify.
The other issue with bypass surgery is the use of leg veins as a channel
for the bypass. The veins do not last long and tend to re-block after seven
to 10 years. This has to do with surgical techniques, the quality of veins
and also the patient factors.
This problem has largely been overcome by the use of arteries as channels
for the bypass. We are born with two chest cage arteries (right and left
internal thoracic arteries), lying just next to the heart, which can be
used as channels of bypass, without any important consequence to the chest
wall.
These chest wall artery channels have proven to be very durable and the
re-blockage rate in them is very low, probably less then 5% in 10 years.
Almost all bypasses nowadays are done using either one or both of these
arteries as bypass channels.
Post-op complications of CABG are mainly attributable to the patient
factors and the use of the heart-lung machine. The good news is that there
has been much improvement in this field.
Cardiac anaesthesia is much better now. The modern heart-lung machines are
better. Cardiac surgeons have learned to do bypasses on a beating heart, to
avoid the use of the heart-lung machine.
Surgical wounds, which used to be about six to eight inches over the breast
bone, are now three to four inches, and some of them are over the ribs
(cosmetically better).
Beating heart surgery also allows for faster post-op recovery.
With conventional CABG, the patient is discharged after about one week and
may take two to three months to recover. With beating heart surgery, they
may stay in the hospital for four to five days and take one to two months
to recover.
Overall, things are getting better, especially with keen competition from
balloon angioplasty.
Balloon angioplasty versus CABG
There are certain types of patients who will definitely do better with
CABG, such as those with certain types of blockages in the left main artery
of the heart, blockages in two or more arteries that are so hard that they
are not possible to balloon, or combinations of these in the context of
poor heart function.
In the past, before the era of drug-eluting stents, the list of patients
who could not undergo angioplasty used to be longer, as the bare metal
stents were re-blocking more often.
Nowadays, with drug-eluting stents, angioplasty can be done in most types
of blockages with minimal risk and minimal re-blockage rates.
In this era of drug-eluting stents, angioplasty does rival CABG as a good
and effective method of treating CAD, except in certain specific
categories.
The future
We await further development of the beating-heart surgery technique,
especially large, long-term studies to show its long-term effectiveness.
In the future, we may also see the cardiac surgeon teaming up with the
cardiologist. The cardiac surgeon will bypass the left front heart artery
and maybe the right artery (which they can do well on a beating heart), and
the cardiologist will balloon the left back artery (which the cardiac
surgeon may have trouble getting to easily, on a beating heart), allowing
the patient to have a smaller scar, and quicker recovery.
As always, it is important to remember that the best surgery is no surgery.
Prevention of heart disease is the best strategy.
This article is contributed by the Federation of Private Medical
Practitioners Associations Malaysia. For further information, e-mail
starhealth@xxxxxxxxxxxxxx The information provided is for educational and
communication purposes only and it should not be construed as personal
medical advice. Information published in this article is not intended to
replace, supplant or augment a consultation with a health professional
regarding the reader?s own medical care. The Star does not give any
warranty on accuracy, completeness, functionality, usefulness or other
assurances as to the content appearing in this column. The Star disclaims
all responsibility for any losses, damage to property or personal injury
suffered directly or indirectly from reliance on such information.
http://thestar.com.my
=========================end, and/or end quote================
-pluto
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