by Tracy Blankenship

Created on: September 01, 2009   Last Updated: September 25, 2009

The coronary arteries begin just centimeters from the beginning of the aorta, at the aortic root. There are two main arteries, the right coronary and the left. As these encircle the heart, they branch off into smaller and smaller arteries and arterioles which bring oxygenated blood to the heart muscle. Blockages or narrowing in these small diameter vessels create areas of injury called ischemia (is-key-me-ya). To prevent permanent damage to the heart muscle (myocardium), adequate blood flow must be reestablished. Coronary artery bypass grafts (CABGs) are a frequent treatment method for reestablishing blood flow to the myocardium.

Commonly referred to as "open heart" surgery, bypass grafting is actually performed on the surface of the heart. A suitably sized vessel is harvested from its normal place and reattached in such a way that blood can be rerouted around the blocked or narrow part of the coronary artery. The vessels used are either veins or arteries.

By far the most common vessel used for bypass surgery is the greater saphenous vein, found in the leg. Previously harvested as a free graft by making an incision starting at the ankle and extending it to the groin, either in one long incision or multiple smaller ones, "endoscopic" vein harvesting is now a popular and less traumatic method of obtaining the vein graft. In the endoscopic technique, a small incision is made near the knee and a thin, long lens is inserted into the leg, allowing the vein to be visualized and the branches identified, cut, and cauterized with no further incisions needed. A smaller stab incision may be made at the groin in order to completely tie off the top part of the saphenous vein. The vein has tiny valves in it, which must be removed or the vein must be reversed in orientation to prevent the valves from obstructing the blood flow. Once the vein is prepared, it is sewn (grafted) onto the target coronary artery. The vein can be used several times, either by cutting into smaller pieces or by sequencing or wrapping the vein along several bypass areas the entire length. Smaller pieces require that each one be attached to the aorta, while sequencing requires one attachment to the aorta, but there are several "ports" made along its length.

Another vessel that has been used with even better results is the internal mammary artery. The left internal mammary artery (LIMA) is uniquely suited to grafting the left anterior descending (LAD) artery, which supplies the left ventricle, the chamber

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