Coronary arteries are the small blood vessels that supply the heart muscle with oxygen and nutrients. Fats and cholesterol can accumulate inside these small arteries, and the arteries can gradually become clogged. (This buildup of fat and cholesterol plaque is called atherosclerosis.)
When one or more of the coronary arteries becomes partially or totally blocked, the heart does not get an adequate blood supply. This is called ischemic heart disease or coronary artery disease (CAD). It can cause heart pain (angina).
Sometimes it does not cause pain until the blood supply to the heart becomes critically low, and the muscle begins to die. The first symptom of CAD in this case may be a potentially deadly heart attack (myocardial infarction). Symptomless CAD is especially common in diabetics.
Heart bypass surgery creates a detour or "bypass" around the blocked part of a coronary artery to restore the blood supply to the heart muscle. The surgery is commonly called Coronary Artery Bypass Graft, or CABG (pronounced "cabbage").
After the patient is anesthetized and made completely free from pain, the heart surgeon makes an incision in the middle of the chest and separates the breastbone.
Through this incision, the surgeon can see the heart and aorta (the main blood vessel leading from the heart to the rest of the body). After surgery, the breastbone will be rejoined with wire and the incision will be sewn closed.
If a vein from the leg (the saphenous vein) is to be used for the bypass, an incision is made in the leg and the vein removed. The vein is located on the inside of the leg running from the ankle to the groin.
It normally does only about 10% of the work of circulating blood from the leg back to the heart. Therefore, it can be taken out without harming the patient or adversely affecting the leg. It is common for the leg from which the vein is taken to swell slightly during recovery from the surgery, but this is only temporary and treated with elevation of the leg.
The internal mammary artery (IMA) can also be used as the graft. This has the advantage of staying open for many more years than the vein grafts, but there are some situations in which it cannot be used.
The left IMA or LIMA is an artery that runs next to the sternum on the inside of the chest wall. It can be disconnected from the chest wall without imparing the blood supply to the chest. It is commonly connected to the artery on the heart that supplies most of the muscle, the left anterior descending artery or LAD.
Other arteries are also now being used in bypass surgery. The most common other artery used is the radial artery. This is one of the two arteries that supply the hand with blood. It can usually be removed from the arm without any impairment of blood supply to the hand.
In the traditional surgery, the patient is connected to the heart-lung machine, or bypass pump, which adds oxygen to the blood and circulates blood to other parts of the body during the surgery. This is necessary because the heart muscle must be stopped before the graft can be done.
One end of the graft is stitched to an opening below the blockage in the coronary artery. If the grafted vein is from the leg or the radial artery, its other end is stitched to an opening made in the aorta. If the grafted vessel is the mammary artery, its other end is already connected to the aorta.
The entire surgery can take four to six hours. After the surgery, the patient is taken to the Intensive Care Unit. For a few days after the surgery, the patient is connected to monitors and tubes.
Other techniques to do this surgery are used more and more frequently. One popular method is to avoid the use of the heart-lung machine. This is called off-pump coronary artery bypass or OPCAB. This operation allows the bypass to be created while the heart is still beating.
The advantage here is that use of the heart-lung machine can lead to some loss of memory and mental clarity, while with this technique (OPCAB), that risk is reduced because the heart isn't stopped, and the blood isn't oxygenated externally.
Another alternative is the use of smaller incisions that avoid splitting the breastbone. This is referred to as Minimally Invasive Direct Coronary Artery Bypass or MIDCAB.
Recently, coronary bypass surgery is being performed with the aid of a robot, which allows the surgeon to perform the operation without even being in the same room as the patient.
