Coronary Artery Bypass Graft (CABG)

Contributing Author, Cardiothoracic Surgeon

Most patients learn of their need for coronary artery surgery after they present to the ER complaining of chest pain, shortness of breath or pain radiating to their jaw or down the left arm. Other patients notice a pressure-like sensation often described as an elephant standing on their chest. An EKG is usually requested and this study may show the general area of the heart which is at risk.

The muscle in this area of the heart may show characteristic electrical changes that alert the physician to possible heart damage. If the patient is thought to have an acute heart attack or MI, thrombolytic therapy or clot buster drugs may be given in the ER to dissolve blood clots in the coronary arteries. Once stabilized, the patient is usually scheduled by the cardiologist for a cardiac catheterization.

Cardiac caths are routine x-ray studies during which a small amount of dye is placed in the coronary arteries to search for blockages. If the blockages cannot be handled by balloon angioplasty or stents or atherectomy techniques, then surgery is recommended to bypass the blocked arteries. The patient also may undergo an echocardiogram prior to surgery and following surgery to determine the overall contractility of the heart muscle.

Since the early 1960ties, the operation to bypass blocked arteries in the heart has been called coronary artery bypass grafting or C. A. B. G. In recent years, cardiologists have been able to balloon open or angioplasty many blockages in the main coronary arteries and, on some occasions, an atherectomy technique has been available to actually cut away the plaque in these arteries. Despite all of these technical improvements, coronary artery bypass surgery still remains the most frequently performed cardiac surgery in the United States.

Saphenous veins from the legs and internal mammary arteries from the chest are usually used as grafts. In 1980, Loop and associates at the Cleveland Clinic reported a series of 646 patients who were restudied 48 months after their surgery. They noted that 81% of vein grafts harvested from the legs remained open or patent at that time interval. The patency of internal mammary artery grafts for the same period was 95%. The internal mammary artery is a small artery which is detached from beneath the breast bone and can be used to bypass some of the blocked vessels found on the surface of the heart.

In 2000, some 20 years later, the patency rate for vein grafts has improved to about 89% at one year and internal mammary artery graft s remain open 97% of the time. The reason for the superior long-term results of internal mammary artery bypass grafts is because the artery is mobilized for grafting along with the small arteries and veins which feed it, the chest wall fat and muscle.

This technique maintains the homeostasis of the artery and its endothelium or inner lining remains intact. Free grafts such as saphenous vein grafts or radial artery grafts do not have this pedicle and are subject to ischemia or sloughing of their endothelial linings. Unfortunately, endothelial damage can lead to stricture or occlusion of the artery or accelerated atherosclerosis. The point being that internal mammary bypass provides the best conduit to supply blood to the heart and this seems to hold up over time better than any other type of material. Plastic grafts, while often used in peripheral vascular surgery, do not stay open because of the small sizes need for coronary bypass surgery.

Now for the bad news. There are several disadvantages that limit internal mammary artery grafting. One is the technical problem of mobilizing the artery. Secondly, there are only two internal mammary arteries and their length is often not sufficient to reach the back wall of the heart well. A third problem is that flow through the internal mammary artery must be equivalent to the flow in the artery to be grafted.

In other words you must have a pretty good size match for this technique to work and the bypass to stay open. In diabetic patients or patients with severe emphysema or fragile breast bones, the artery may be of poor quality and not suitable for grafting purposes.

Recommendations:

1. If you have chest pain which is new in onset, or a pressure sensation often accompanied by sweating and the feeling that something is wrong go to the nearest ER.
   
2. If your EKG suggests an acute MI, you may be told that you need a clot buster like t-PA to dissolve blood clots.
   
3. The next step in your workup may well be a trip to the cath lab to discover the exact location of blockages in the coronary arteries of your heart.
   
4. If your cath films shows several blockages, coronary artery bypass may be your best chance for recovery of most of your cardiac muscle function.
5. Lastly, saphenous vein grafts or internal mammary grafts should give you a new lease on life, but you will most probably have to change your lifestyle in the future to avoid another trip to the OR in 10 years.