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The most common type of heart valve surgery is bypass grafting. This is often shortened to "CABG," for Coronary Artery Bypass Grafting.
Image from AHA
The arteries that deliver blood to the heart muscle are called coronary arteries. The term coronary comes from the Latin word for "crown," because the heart arteries looked like a crown to early anatomists.
Blockages can form in the arteries of the heart, the coronary arteries.
It is not known exactly why blockages form in the coronary arteries, but risk factors such as diet, lack of exercise, genetics, cholesterol, immune system, stress, and smoking certainly contribute to Coronary Artery Disease - the medical term used to describe blockages in the arteries.
It is thought that the earliest signs of blockages in the coronary arteries occur early in life, as early as childhood.
God made the coronary arteries bigger than they need to be; that is, the blood flow in the coronary arteries is hardly ever at full capacity. The heart muscle can pretty much always get as much blood - and thus oxygen - as it needs.
But blockages take up space in the arteries. As the blockages worsen, they can get to the point where the blood flow is limited.
When the blood flow to the heart muscle is inadequate, the heart muscle suffers. If the blockages slowly worsen over time, the suffering heart muscle may not cause severe damage but may cause chest pain or pressure, which is called angina.
If the blockages worsen or clog up all of a sudden, then a heart attack can occur. With a heart attack - known as a myocardial infarction - the heart muscle is damaged. If the blood flow is not quickly restored, the damaged muscle may turn into scar. Extensive damage and scar-formation can severely weaken the heart.
A myocardial infarction - a heart attack - can be life-threatening. You should always seek immediate medical attention if you think you may be having a heart attack.
Not all patients experience pain when the heart muscle suffers from impaired blood flow. In particular, patients with diabetes often do not experience chest pain. Some patients may feel short of breath, or winded, or they may feel tired or fatigued. Some patients may not experience symptoms.
If a patient has on-going chest pain (angina) at home, a stress test can help determine if the pain is likely to be from blockages in the coronary arteries. There are different types of stress tests and a cardiologist can determine which is the best for a particular patient.
There are stress tests which involve walking and jogging on a treadmill and there are stress tests which use medicines to stress the heart.
If a stress test is positive and it looks like blockages in the heart arteries may be causing impaired blood flow to the heart muscle, or if a patient has a heart attack, a cardiac catheterization is done to better evaluate for blockages.
A cardiac cath is done thru an artery in the groin or the wrist. A special, very small catheter is placed thru the artery up into the arteries of the heart; dye is injected, which fills the arteries of the heart. An x-ray is performed, which shows the arteries.
If any of the arteries have a narrowed area, then there is likely a blockage there.
Here is an example of a cath image, with normal arteries. You may appreciate how smooth the arteries look. There are no narrowed spots. A cath would involve several different looks at the arteries from different angles, to be sure no blockages are missed.
Here is an example of a cath image, with abnormal arteries. You may appreciate how it looks like part of the arteries are missing! There is a very tight spot where very little blood is getting past. This is a bad blockage - so this patient has Coronary Artery Disease. A blockage like this is called a stenosis, a narrowed area.
An interesting thing about CAD is that usually the blockages, the stenoses, are not all the way down an artery. Like the stenosis in the pic above, a stenosis is in one spot. A patient may have many blockages, of course, but usually there are areas of an artery which are relatively normal. Often, the stenoses occur at places where the arteries branch.
If blockages have been found on cath and are impairing blood flow to the muscle, usually there are 3 options for treatment:
Medications can be used to help slow the worsening of blockages.
However, there is no medicine that has been shown to make the blockages go away, or even to shrink the blockages.
There are some companies that claim certain vitamins or special elixirs will melt away blockages, but these have never been proven effective in scientific studies.
Likewise, exercise is helpful to keep the body and the heart strong, but exercise cannot be expected to eliminate or even reduce the blockages.
So medicines and exercise are helpful in managing CAD long term, but usually are not enough to help a patient who has angina or a heart attack, unless the patient cannot have stents or bypass surgery for some reason.
Stents can be used to open up a blockage. The stent is inserted thru the artery in the groin or wrist, guided up inside the blockage, and then opened with a tiny balloon.
The placement of a stent is called PCI, which stands for Percutaneous (thru the skin) Coronary Intervention. It is NOT open-heart surgery.
Stents are usually made of metal. Many of the stents used now are drug-eluting stents, meaning the stent is coated with a time-release medication. The stent releases a tiny amount of medication into the artery after the stent is placed. The medication released is designed to help prevent scar formation and helps to keep the stent from clogging.
Often, when a new stent is placed, the patient will need to take Plavix, which is a platelet inhibitor. It is like Super-Aspirin. It works to keep platelets from clogging up a stent. Strictly-speaking, Plavix is not a blood thinner, though many people call it a blood thinner.
There is a limit to how many stents can reasonably be placed at one time. This will vary depending on the patient and the situation and is decided by the cardiologist performing the procedure.
In general, stents to do not work very well for blockages at branching points, or at least, they can be very difficult to put in.
Several studies have shown that patients with diabetes who have blockages in 3 or more coronary arteries will live longer (statistically-speaking) by having bypass surgery rather than stents. This data is so compelling, in fact, that many patients without diabetes are also treated with bypass surgery rather than PCI, when 3 or more arteries are blocked.
Bypass surgery, aka CABG, can be used when medications and stents are not enough to get blood to the heart muscle.
CABG is a bit like adding new "pipes" on the heart, pipes which will carry the blood around the blockages. The blockages are not cut out or removed or opened. Instead, the blood is re-routed around the blockages.
The number of new pipes or bypass grafts needed is often the same as the number of blockages. A patient who has 3 blockages and requires three bypass grafts would be getting a CABG x3. Non-medical people would call this "triple bypass."
The new pipes used are from the patient. You would not want PVC or lead! Typically, an artery from the breastbone called the Left Internal Mammary Artery, or LIMA, is used. Often, vein from the leg is also used to make the new pipes.
Most patients do not need to take Plavix or any other medication specifically for the bypass grafts/new pipes after operation. However, this can vary and of course a patient should comply with the recommendations of his or her surgeon.
If CABG is needed, there are a couple of options on how to do it:
Sternotomy is the usual way to access the heart for bypass surgery aka CABG.
Sternotomy allows for access of all sides of the heart and multiple bypass grafts can be performed.
The sternal bone is fixed back together at the end of the operation with stainless steel wires. These wires hold the edges of the bone together so they can heal. It generally takes 2 months for the bone to heal, so Dr. Pool recommends not lifting anything heavy (over 10 lbs) for 2 months after sternotomy. The wires do make a metal detector go off, BTW, at least not at the sensitivity of the detectors at the airport.
Once the bone is healed, the wires could theoretically be removed and the bone would still stay together but there is usually no benefit in going back for another procedure simply to remove the wires.
The risk of sternal wound problems - such as an infection or a breakdown in the wound - is usually around 1%. Even diabetic patients usually have a low risk of wound problems with sternotomy.
It is possible to perform CABG with a robotic approach.
There are several variations - the one Dr. Pool uses is to harvest the LIMA with the daVinci robot and then perform a hand-sewn connection between the LIMA and the LAD, thru a small incision in the left chest.
Dr. Pool only recommends a robotic approach in certain cases. Typically, it is when a patient only needs one bypass graft. Or when one bypass graft plus a stent or two - a combination called a hybrid approach - would fix the problem with the blockages.
A robotic approach has not been proven superior to sternotomy in most scientific studies, though the incision is smaller and overall recovery back to work seems to be slightly shorter.
The risk of sternal wound problems - such as an infection or a breakdown in the wound - is around 1%, which is similar to sternotomy.
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