First, the sternum is cut down the middle with a special bone saw and the chest opened (a procedure known as "cracking the chest" or a median sternotomy). Depending on a number of factors, the surgeon may decide to place the patient on cardiopulmonary bypass ("on-pump") or use suction-stabilizing devices to hold the heart still while sewing the anastamoses ("off-pump"). Blood vessels are harvested from elsewhere in the body for grafting. Sometimes artery end branches supplying tissues near the heart are rerouted to create the bypass.
Typically, the saphenous vein from the leg and the left internal mammary artery (LIMA) are used for the bypass. Veins used either have their valves removed or are turned around so that the valves in them do not occlude blood flow in the graft. LIMA grafts are longer-lasting than vein grafts, both because the artery is more robust than a vein and because, being already connected to the aorta, the LIMA need only be grafted at one end. For this reason, the LIMA is usually grafted to the left anterior descending artery (LAD), which supplies the left ventricle, the part of the heart that pumps oxygenated blood around the body. Alternatively, an artery such as the radial artery from the arm, may be used in place of a vein. This is believed to prolong the life of the grafts but this has yet to be proven.
Prognosis following CABG depends on a variety of factors, but successful grafts typically last around 10-15 years.
CABG may also be indicated in other specific circumstances, or when an individual patient is experiencing severe angina pectoris that cannot be controlled with medicines alone.
In the 1970's and 1980's, cardiothoracic surgeons discovered that an artery from the inside of the chest wall, the internal thoracic artery (also called the internal mammary artery), could be used instead of vein for the bypass grafts and that it stayed open longer than saphenous vein grafts.
Potential complications of CABG include bleeding or infection, stroke (which is primarily related to age and history of previous stroke), kidney failure (related in large measure to the kidney function before the surgery), and heart attack during or after the surgery.
Patients with a 60% or greater stenosis of the left main coronary artery have survival benefit from surgery in comparison to medical treatment or angioplasty, and these patients should receive this treatment unless contraindications are present.
Further investigation is needed to define the mechanisms underlying the better observed outcome in diabetic patients treated with CABG in comparison to angioplasty.
Therefore, for patients with an overriding goal to avoid CABG, the choice of PTCA will be 70% effective in achieving the goal with one or more PTCAs but without an additional penalty of greater risk of myocardial infarction.
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