Conduits in Coronary Artery Bypass Grafting

Dateline: 08/10/97

Coronary bypass - also called CABG - is the single most common open heart operation performed in most parts of the world !

When a coronary artery is blocked, an alternate route of blood suppy may be created surgically. Using a variety of conduits (leg veins, or arteries from another part of the body) a connection is made between the major blood vessel of the body - the aorta - and the blocked coronary artery, beyond the area of obstruction. In this way, even though nothing is done about the block itself, blood is provided to the heart via the "bypass"....hence the term, coronary bypass surgery.

Which conduit ?...When ?...Why ?...

SAPHENOUS VEIN GRAFTS

The first CABG operation was performed in 1962 at Johns Hopkins, Baltimore, by David C.Sabiston Jr. He used a segment of vein from the leg (called the long saphenous vein) of the patient to fashion a pathway between the aorta and diseased coronary arteries. Even today, this is one of the commonly used conduits.

Its main drawback is the possibility of atherosclerotic plaque-formation in the vein conduit itself over a period of five to ten years, leading to graft occlusion. This has similar consequences to the original disease.

ARTERIAL GRAFTS

Internal Thoracic Artery (ITA) or Internal Mammary Artery (IMA)

A little known Russian, Kolessof, performed the first CABG operation using another artery as the conduit. On the inside of the chest wall is a large arterial branch called the Internal Thoracic Artery (ITA). (Incidentally, I like the acronym....Right ITA is RITA...and that's the name of my earliest girl friend ! )

This artery is more or less similar in size to a coronary artery, and by it's close proximity to the coronaries, is easy to use as a bypass graft to diseased arteries. It wasn't until much later that the significance of using ITAs for grafting was understood. After 10 years, 95 percent of these conduits remained free of plaque and repeat obstruction, and this instantly made it the preferred conduit over saphenous vein ! Today, this is the CONDUIT OF CHOICE to perform bypass surgery, and significantly improves long term survival after performance of this operation.

Other Arteries that may be useful as conduits

When the advantages of using arteries to bypass the coronaries were recognized, many different surgeons used their imagination to expand the choice of arteries to use as conduits. Today, the possible targets are

• Gastroepiploic artery - which supplies the stomach and intestines
• Radial artery - which is the artery that nourishes the forearm and hand
• Inferior Epigastric Artery - which runs in the wall of the lower abdomen
• Subscapular artery - on the back of the chest
• Splenic artery - supplies the spleen
• Intercostal artery - which runs just inside the rib cage

Of these, only the radial artery and gastro-epiploic arteries are commonly used. Though none has been proven better than ITAs, expectations are that they will be atleast as good, and that the benefits of a bypass operation will then be more long lasting.

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