Coronary Artery Bypass Surgery: The Best Answer to Coronary Artery Disease
MY PERSONAL PERSPECITVE:
As a cardiac surgeon I have a clear bias in favor of the coronary bypass operation. It is a wonderful operation – it is low risk and it saves lives. It is simple in concept, yet allows the technical gifts of the expert surgeons who practice this craft to distinguish themselves from their less gifted colleagues. Unfortunately, I have seen this operation performed poorly and I have rescued patients from their poor results. I have also seen patients who were perfect candidates for a scheduled operation suddenly placed in a high-risk emergency category because of Angioplasty.
Let me explain the history of this operation, how and why it works, and the benefits of elective (non emergency) coronary artery bypass surgery (CABG). You need this information to be proactive in the selection of care for your coronary artery disease.
HISTORY
In the late 1950’s Mason Sones at the Cleveland Clinic perfected x-ray visualization of the coronary arteries. The lesions responsible for chest pain symptoms, heart attacks and death could now be defined. But the available therapies were limited. There was no successful mechanical intervention. Only medications could be directed at the symptoms of the disease.
The only therapies available were long and short acting nitroglycerin medications and drugs directed at decreasing cardiac work and its oxygen demands (Beta blockers). Statin drugs to lower cholesterol and the rate of growth of the plaque material had not been developed. Believe it or not, some recommended long periods of bed rest.
When I arrived at the National Heart Institute in 1966 the history of surgery for coronary artery disease was filled with failures. There were at that time two widely attempted operations: 1. Endarterectomy: where the calcium-cholesterol plaque was removed. This surgery was not often successful and carried a high mortality rate. 2. The Vineberg procedure, where one end of a chest artery was placed directly into the heart muscle with the theory that its branches would grow into the heart muscle and solve the problem of inadequate blood supply. Curiously, the theory proved to be correct, but the ingrowths of new arteries took months. There was no immediate benefit to the heart. Consequently, the mortality rate was high. Against this backdrop of failures, any new operation was greeted with great skepticism.
The work of Mason Sones had attracted the attention of Rene Favaloro, an Argentinean, who traveled to Cincinnati and became a Fellow in the Cleveland Clinic surgical program. He began research simulated by the X-Ray pictures for the coronary arteries produced by Sones. Favaloro finally arrived at workable solution for patients with coronary artery disease. X-Rays had shown that even when all three major coronary arteries were severely diseased, the aorta just above the heart was normal. Favaloro seized on this fact to invent his simple and effective treatment for coronary artery disease.
In the late 1960’s Rene Favaloro completed his operation on his first group of 100 patients with coronary artery disease. The results were presented in 1967 to the American Association of Thoracic Surgeons. His operation revolutionized the treatment of coronary artery disease.
Conceptually, Favaloro’s operative solution was simple and has not changed to this day - get normal blood flow to the heart muscle below the point of arterial narrowing. His procedure rapidly was incorporated into the arsenal for the treatment of coronary artery disease in every University Hospital, and soon thereafter into community hospitals around the country. By the late 1970’s it was the most common operation in the United States.
FAVALORO’S OPERATION
Coronary artery disease consists of narrowing in the arteries serving the heart muscle. The natural history of the disease is the progression of the narrowing in these arteries with cholesterol –calcium plaque to closure of the artery. The closure results in death of the muscle tissue served by the artery, and ultimately the death of the patient.
Favaloro’s operation accomplished a simple mechanical task. The bypass graft procedure consisted of creating a bridge-conduit (bypass) from the aorta just above the heart to the normal portion of the coronary artery below the point of narrowing. Favalaro used the saphenous vein; a superfluous vein in the thigh, to create the bridge-conduit. One end of the conduit is sewn into the normal aorta above the heart. The other end is sewn into the normal portion of the coronary artery below the narrowing.
The skill of the surgeon is critical. Selection of a poor vein segment and lack of precision in the sewing technique can result in early closure of the bypass.
Other causes of closure can come into play a few years after surgery. These closures are probably related to marginal blood supply to the wall of the vein graft since this vein has been removed from its normal location and blood supply.
INNOVATIONS TO CABG SURGERY
Since the original operation, refinements have been added. In the late 1980’s a revolutionary change took hold directed at bypass closures. A chest wall artery began to be used as the conduit. This artery bypass maintains its normal blood supply because that blood supply comes from the arterial graft itself. It is more technically demanding to use these arterial conduits, but the reward is a more permanently open conduit. This innovation continues to this day along with the use of other artery conduits taken from the arm, and occasionally, the upper abdomen.
Recently, minimally invasive techniques have been used for CABG. Small incisions are made in the front of the chest. A scope is introduced through these incisions to remove the chest wall artery from the chest wall and create the bypass. The proponents of this approach, site the advantage of not placing the patient on the heart-lung machine in addition to the limited healing time required; however, I feel the use of this minimally invasive approach is not wise because the disadvantages outweigh the advantages for the following reasons.
First, the artery below the point of bypass cannot be protected. In order to sew the graft in place, the blood flow in the artery has to be stopped. Within 20 minutes at normal body temperature the muscle served by that artery will be dead.
Secondly, realistically only one bypass, that of the left anterior descending artery, can be done using this technique. The surgeon is confined to working only on the front of the heart and is limited by his field of vision through the scope and the physical inability to manually move the heart to visualize its other surfaces.
Third, since the heart is beating the sewing technique could be compromised.
I feel the best operation would be to have multiple grafts as I explain below in the section “Your operation”.
In gifted skilled hands, today, the CABG operation can be accomplished with a less than one percent mortality rate and be successful for twenty plus years. The patient no longer is exposed to the risks of coronary artery disease.
THE SURGEON
The patient facing CABG must play an active role with the Cardiologist in selecting a surgeon. The training of the Heart Surgeon selected needs to be scrutinized.
A surgeon’s personal experience with the technically demanding CABG procedure should be defined. Especially with the advent of the arterial conduit, the skill of a selected surgeon cannot be over emphasized.
The volume of such procedures a surgeon has performed is extremely important along with his personal results. I personally would not even consider selecting a surgeon who does less than 100 procedures per year. Traveling to find the best Cardiac Surgeon might be necessary and should not be ruled out.
THE DISADVANTAGES OF EMERGENCY SURGERY
In a previous article devoted to Angioplasty, I mentioned the distinct advantages of elective CABG versus emergency CABG. Let me expand on that premise.
1. In CABG after a failed Angioplasty the entire concept of Surgeon selection is lost. You will be operated on by whoever is immediately available.
2. In emergency situations substitutes may be taking the place of the regular members of the open heart surgical team.
3. The closure of the artery after attempted Angioplasty can occur immediately or within hours or days. At normal body temperature death of the served muscle occurs in twenty minutes. That does not allow enough time for the surgeon to ready himself, his team of nurses, and the heart lung machine technician. In the first twenty minutes some heart muscle will definitely be lost and the amount of lost muscle will have a definite effect on the mortality of the patient. In the extreme, if 50% of the muscle is lost, the mortality rate can be 50% or greater.
One might question -why then should any operation be attempted?
The answer lies in a miracle of the body and the heart that is referred to as the “halo zone”.
The only reason to attempt an operation in such circumstances is that the heart muscle death process is complicated. The middle or core of muscle served by the closed artery will definitely be lost. But there is a zone surrounding this absolute lost zone I will refer to as the “halo zone”. The halo zone muscle is stunned by the artery closure, and cannot function, but it does remain viable. If blood supply is reestablished to that zone, it can function again. Though the halo zone cannot be accurately defined in many cases it is larger than the core of lost muscle. Depending on the blood supply surrounding and giving life to the halo zone, the size of this zone can decrease in the first few hours after Angioplasty. Emergency surgery is done to bring the halo zone to full function. The patient is now blessed with a closer to normal amount of heart muscle.
4. In an emergency CABG, no screening can be done for carotid artery disease.
The carotid arteries serve the brain. Disease in these arteries is responsible for stroke.
A patient with coronary artery disease should be aware that it is not unusual to have some degree of arteriosclerosis through out their circulation.
During CABG the heart is stopped and the patient placed on a heart lung machine to sustain his circulation. It is necessary to bring the heart to a standstill to allow the work to be completed on the small coronary arteries.
When on the heart lung machine the patient will have a lower blood pressure than normal, strokes are a major and not uncommon problem with CABG.
In an elective operation screening for carotid artery disease should always be done. Consequently, the carotid arteries will be repaired as necessary prior to placing the patient on the heart lung machine and the risk of stroke is minimized.
5. In emergency circumstances time is an important variable. The quickest CABG operation would be to use a vein conduit. Arterial conduits are superior, but the emergency takes that option away.
So if you decide on CABG, do it electively. Select your surgeon and hospital carefully. Do not rule out travel to the best hospital and the best surgeon.
YOUR OPERATION
- If the surgeon is good and experienced he will probably bypass more arties than the one targeted in the Angioplasty.
In the early 1960’s, William Roberts, a pathologist at the National Heart Institute, published a series of papers defining the coronary artery disease present in patients experiencing sudden death. His work clearly established that there is no such thing as single or double coronary artery disease. All coronary arteries are involved.
Maybe an arteriogram reveals only one artery has the 70% or greater narrowing – the standard for surgical intervention. Lesser narrowings, i.e. 30% to 50%, or no other narrowings may be apparent on the arteriogram. But in these arteries, or at sites not suspected of disease on the arteriogram, severe disease can be present. The arteriogram only visualizes the interior of the artery, not the wall of the artery which contains the disease. In surgery, the surgeon can feel the calcium in arteries and see inflammation around lesions which do not appear dramatic on the arteriogram. An intraplaque arterial rupture in such a diseased artery could bring it to a critical closure level at any time.
The findings during surgery may lead the surgeon to perform more bypass grafts than were originally thought to be necessary.
- Discuss with your surgeon that you want as many conduits as possible to be arterial conduits.
- More grafts rather than fewer graphs could well be the safest operation.
- Have your operation early in the week. Weekend coverage in the hospital ICU is not as optimal as weekday nursing coverage.
- Have your surgeon schedule your operation for the first of his day. If a complication such as excessive bleeding occurs, it will surface in the afternoon and can be quickly solved. In the middle of the night, when the OR has shut down things become more difficult. The OR has to be reopened, staffed, and the surgeon must come from home. Delays are inevitable.
THE REWARDS OF CABG SURGERY
An elective CABG operation is the best option. The mortality rate is low and the benefits are long lasting.
The disadvantages of an emergency procedure disappear. The most common and severe complication, stroke, is avoided with carotid artery screening. The surgeon has the opportunity to discover disease in the maximum number of arteries and repair more arteries than just an acutely damaged artery. Arterial conduits, instead of vein, can be used to their maximum availability. There is no unexpected loss of heart muscle.
The patient has the opportunity to choose both the hospital and the surgeon. A scheduled operation assures the best operative team.
There is, of course, the psychological burden of an operation and 5-7 days of hospitalization after surgery. A recovery time at home of about a month is necessary before activities approach normal. Repeat hospitalizations for coronary artery disease should be unusual and rare. The reward is that coronary artery disease is removed from your expected future.