What is coronary artery bypass surgery?
Coronary artery bypass surgery is a procedure in which a blockage in a coronary artery is bypassed to restore normal blood flow through the artery. Coronary arteries are blood vessels that carry oxygen and nutrients to the heart. The blockage can be bypassed with a new vessel made from part of one of your veins (usually from the leg) or another artery (usually in the chest).
When is it used?
Coronary artery bypass surgery may be necessary when arteries to your heart become narrowed or blocked.
If more than one artery is blocked, you may need more than one bypass. The location and degree of coronary artery blockages are determined before surgery with a procedure called heart catheterisation, or coronary angiogram.
How do I prepare for coronary bypass surgery?
Plan for your care and recovery after the operation. Allow for time to rest and try to find other people to help you with your day-to-day duties. Follow instructions provided by your doctor. Shower and wash your hair the night before the procedure. Eat a light meal, such as soup or salad, the night before the procedure. Do not eat or drink anything after midnight and the morning before the procedure. Do not even drink coffee, tea, or water.
What happens during the procedure?
You will be weighed the morning of the procedure. Later after the you will be weighed again to see if you are retaining water. To prevent infection, your legs, groin, and chest (if necessary) will be shaved.
You may be given a mild sedative to help you relax before the general anaesthetic is given. The anaesthetic will relax your muscles, keep you from feeling pain, and put you in a deep sleep.
Coronary artery bypass surgery is performed by a team of surgeons and lasts from 2 to 6 hours, depending on how many blood vessels need to be bypassed. One cut (incision) is made in the center of the chest at the breastbone to expose the heart. Another incision may be made in the leg to remove a vein for the new blood vessel that will bypass the blockage. (Otherwise, an artery in the chest, called the internal mammary artery, is used.) You are then connected to a heart-lung machine that supplies oxygen to your blood and circulates it back into your body while the surgery is performed.
If a piece of vein is used for the bypass, one end of the new blood vessel is sewn into the aorta (the main artery from the heart to the body). The other end is sewn into the area below the blockage in the coronary artery. If the mammary artery is used, the lower end of the mammary artery is cut and reattached to the coronary artery beyond the blockage. The blood then uses the new vessel as a detour to bypass the blockage before returning to its normal path.
When the surgery is finished, you are disconnected from the heart-lung machine, your breastbone is closed with wire, and your chest is closed with stitches or staples.
What happens after the procedure?
After surgery, you are placed in an intensive care unit (ICU) for several days for observation and monitoring. A constant electrocardiogram (ECG) monitor will record the rhythm of your heart. You will receive respiratory therapy to prevent any complications in your lungs, such as a collapsed lung, infection, or pneumonia. A nurse or therapist will give you a breathing treatment every few hours. It is extremely important to cooperate and ask for pain medication if you need it.
Therapy may include:
a.. deep breathing exercises
b.. coughing while holding a pillow against your chest to protect your breastbone
c.. chest percussion, which is a gentle slapping on the back to help loosen lung secretions that may have accumulated after surgery
d.. moving your legs to reduce the chance of blood clots.
While in the ICU, you may have the following tubes in your body to help in recovery
.. a breathing tube in your mouth that goes into your lungs and is connected to a ventilator to help you breathe
b.. a tube through your nose and down to your stomach to drain out natural fluids that may cause discomfort when you are not eating
c.. a catheter to empty your bladder
d.. intravenous (IV) tubes in your arms or neck for fluids, nutrition, and medications
e.. chest tubes to drain blood from your chest cavity and to help detect any excessive bleeding in your chest
f.. an arterial line in your wrist to measure the pressure of the blood flowing through your arteries.
Sometime during the first 1 to 3 days after surgery, the tubes are removed and you are moved to an intermediate care unit. You will stay in this unit until you are ready to leave the hospital. You will have physical therapy, which includes walking around the hospital and other strengthening activities. You will learn how to move your upper arms without hurting your breastbone, and you will receive more respiratory therapy. You will be told about specific foods to avoid when you get home, such as foods high in fat, cholesterol, and sodium. Occupational therapy will help you learn how to take it easy while doing daily activities.
What are the risks associated with this procedure?
a.. Depending on your age and the condition of your heart, there is about a 2% to 10% risk of death from this operation.
b.. There are some risks when you have general anaesthesia. Discuss these risks with your doctor.
c.. There is a risk of infection or bleeding from this procedure.
d.. A bypassed vessel may become blocked again, which might require another heart catheterisation and surgery.
e.. There is a risk of stroke during the operation.
How can I take care of myself?
Follow the full treatment prescribed by your doctor, including all medications. In addition:
a.. Get plenty of rest.
b.. Plan at least two rest periods during the day (more if you still are tired).
c.. Enjoy the support and visits of family and friends, but keep visits short and allow yourself time to rest.
d.. Learn deep breathing and relaxation techniques.
e.. Talk about your feelings.
f.. Stop smoking.
g.. Lose weight slowly if you are overweight.
h.. Follow a healthy, well-balanced diet that is low in salt, saturated fats, and cholesterol.
i.. Weigh yourself every morning to help detect a water retention problem.
j.. Develop a regular exercise program prescribed by your doctor.
k.. If you feel constipated, ask your doctor for a stool softener or a fiber-based laxative. (Constipation is a common problem after having anaesthesia and being physically inactive.)
l.. Wear support hose to prevent swelling and circulatory problems in your legs. Putting powder on your legs can help you pull hose on more easily. Smooth out any wrinkles to avoid pressure spots.
How can I prevent problems from occurring during recovery?
a.. Follow your doctor’s recommended schedule of activity after surgery.
b.. Have someone help you with your bath or shower if you feel dizzy. Consider using a waterproof chair in the shower for safety.
c.. Avoid extremely hot water in your shower, bath, or hot tub because it can affect your circulation and cause light-headedness.
d.. Initially, avoid lifting anything heavier than 5 to 10 pounds.
e.. Avoid mowing the lawn, mopping, vacuuming, driving, and any other activities that strain your upper arms and chest until you have recovered.
f.. Avoid driving and sexual intercourse until your doctor tells you it’s okay to resume these activities.
g.. Ask your doctor whether you can drink any alcoholic beverages. When should I call the doctor?
Call the doctor immediately if:
a.. You develop a fever.
b.. You become short of breath.
c.. You have worsening chest pain.
Call the doctor during office hours if:
a.. You have questions about the procedure or its result.
b.. You want to make another appointment.
AORTIC VALVE REPLACEMENT OPTIONS
1.1. Pulmonary Autograft (The Ross Procedure)
This is the patients own pulmonary valve. The first pulmonary autotransplant was performed by Dr. Donald Ross at Guy’s Hospital on June 8, 1967, (thus the name the Ross Procedure) and the patient was still doing well 28 years later.
The Ross Procedure considers the patients own pulmonary valve to be the ideal replacement valve for several reasons:
Normal aortic and pulmonic valves are both identical in size, shape and configuration. Both are trileaflet valves.
Even when the aortic valve is deformed, the pulmonary valve is almost always created as nature intended. Thus the pulmonary valve provides the closest identical twin possible for the aortic valve.
The pulmonary valve is usually within a millimeter or two of being the exact right size, is always sterile, and is comprised of living tissue.
Since the autograft comes from the same individual, rejection is never a concern.
Results: The pulmonary autograft transplanted to the aortic position was not calcifying, leaking, or showing signs of degeneration. At 20 years, only 15% of patients required another valve operation, usually replacement of the homograft reconstruction of the right ventricle [Ross 1996]. Patient survival at 20 years is an impressive 80%.
1.2. Mechanical (prosthetic) Valves
A mechanical valve is made from artificial materials. Most commonly, the mechanical valves are made from a material called pyrolitic carbon. This is pure carbon heated and compressed in a trade secret process. The final smooth surface is obtained by layering carbon formed into a gas onto the surface of the compressed carbon. The resulting leaflets are very smooth and resistant to thrombus formation (i.e. clot). Some components of modern mechanical valves are made from titanium or a multi-metal compound called Elgiloy.
The first of these was the Starr-Edwards design, a functioning heart valve made from a steel cage enclosing a silicone rubber ball. Developed in 1961, it was first used to replace the human mitral valve, but had limited success when used as an Aortic valve replacement. One of the more commonly used valves today is the St. Jude bi-leaflet valve.
The major disadvantages of these valves are:
Failure to grow in concert with the growing child.
Lifelong risk of clotting on the valve, leading to stroke
Lifelong risk of clots which freeze the mechanical leaflets
Requirement for lifelong blood thinning agents (i.e. Coumadin)
Complications of anticoagulation (i.e. spontaneous bleeding)
Audible noise when the valve closes (clicking sound)
Risk of late infection (prosthetic endocarditis)
Some mechanical are not large enough for the recipient, resulting in stenosis.
Results: The patient implanted with a mechanical aortic valve continues to run some long term risks of either a stroke or major bleeding episode in the range of 4 to 8% (combined) per year. In addition, the long term survival is 60% at 15 years, with most deaths related to non-cardiac causes.
1.3. Animal Tissue (xenograft) Valves
These first appeared in 1972. The porcine (pig) aortic valve is the most widely used. The pig valves are made from animal heart valve tissue and thus are relatively free from the risk of clotting. This is an advantage in some patients who cannot take anticoagulation medication (pregnant women, patients with brain aneurysms, bleeding intestinal sources, etc.)
The porcine valve is tanned with a stringent chemical called glutaraldehyde, an agent similar to, but stronger than, formaldehyde. This processing toughens the leaflets and cross-links many of the proteins. In doing so, the valve is also rendered less likely to be rejected. However, the tanned leaflets are no longer living tissue.
Results: Calcification of the valve is a problem, and animal tissue valves usually begin to degenerate within 8 to 10 years after implantation. In patients less than 40 years of age, animal tissues valves may degenerate within 5 years of implantation.
1.4. Aortic Homografts
A homograft valve is a human cadaver valve (also called allograft). These valves historically have had problems with sizing and suturing of the valve, along with the expected problems of procurement and long term storage.
Although methods of preservation and long-term storage have improved, these valves have suffered from unique problems when used as an Aortic replacement, such as structural deterioration, difficult implant surgery, and occasional size mismatching.
Results: These valves will last an average of 15 years. Over time, the wall of the homograft aorta surrounding the valve becomes severely calcified, creating increased surgical difficulty at the time of subsequent replacement. Rejection of the aortic tissue may play a role in this form of degeneration.
2. GENERAL QUESTIONS ON THE ROSS PROCEDURE
2.1. What are the disadvantages of the Ross Procedure?
No matter how much improvement has been made in the surgical techniques for performing the pulmonary autotransplant procedure, there are still some drawbacks.
One disadvantage is the magnitude of the surgical procedure. It is a very technicaly demanding surgery.
Some critics are concerned that transferring of the pulmonary valve converts a patient with only aortic valve problems to a patient with 2 heart valves now in jeopardy. The potential for premature degeneration of the pulmonary substitute has also been voiced. Fortunately, the long term results now available tend to refute both of these concerns. Results have shown that premature failure of the homograft valve used to replace the pulmonary valve is much more common when human aortic tissue was used in the right side reconstruction, as opposed to human pulmonary tissue. There was only a 74% freedom from reoperation at 5 years when aortic homografts were used for the right ventricular reconstruction. However, there is a 94% freedom from reoperation at 5 years (and 83% at 20 years) when a pulmonary homograft is implanted into the right ventricular outflow tract. The reasons for this dramatic difference are not known.
In summary, the major disadvantages of this operation for the surgical treatment of aortic valve disease are outlined below.
Lengthy operative times (over 2 and 1/2 hours to complete the repair)
Technically more demanding on the surgeons skills.
Cannot be used in every patient (such as those with Marfans syndrome or other connective tissue disorders)
Cannot be effectively combined with other valve operations or coronary bypass (due to the lengthy operative times required).
Limitations in availability of appropriate sized pulmonary homografts for replacing the donor site (particularly in children).
Theoretically converts a single valve patient to a double valve patient.
2.2. What is the ideal candidate for the Ross Procedure?
Who are less than 55 years of age (at the time of anticipated surgery)
Who have a life expectancy of 20 years or more
Who would have problems with being on anticoagulation medication, such as a history of bleeding. (regardless of age)
Who are women of childbearing years
Who have no other major cardiac lesion needing correction (multivessel coronary disease, mitral disease).
Have isolated aortic valve pathology.
Atheletes or the young for whom anticoagulation would carry a higher risk.
The accepted age range for patients having the pulmonary autograft procedure has expanded significantly. Many surgeons view the procedure as a solution for congenital aortic stenosis that can be performed early in life, and quite possibly eliminate the need for multiple aortic valve replacements. As increasing durability of the operation is evidenced, older patients with more active lifestyles become candidates for the procedure. The pulmonary autograft procedure is certainly indicated for young women of child-bearing potential, due to the problems associated with the use of blood thinning agents (Coumadin)