Tuesday, March 21, 2006

Coronary Artery Bypass Graft Surgery Part 1


Coronary artery bypass graft surgery is commonly called CABG (pronounced “cabbage”), bypass, “plumbing job”, etc. The terms all describe what is being done. CABG (the most common acronym) is essentially a plumbing job, done by skilled cardiothoracic surgeons. In CABG the surgeon uses a vein to re-established the blood flow caused by a blockage in the heart artery, almost like what a plumber would do if the kitchen sink was blocked. Although I put this rather simply, it is actually very complicated surgery. This will become obvious as I go along.

A little bit of history. In 1965 Dr Mason Sones discovered the use of coronary angiogram, a technique which allowed us to see the coronary artery in a live person, thereby allowing us to identify blockages accurately. Dr Sones was working in Cleveland Clinic, Ohio, USA. The cardiac surgeon there at that time was a brilliant Argentinean called Rene Favaloro. One day, as the story goes, a young man came in with acute severe chest pains. Dr Sones did an angiogram which showed a right coronary artery blockage. As he was non-responding to medical therapy, he asked Dr Favaloro to help with a new technique that Dr Favaloro was experimenting with in the animal laboratory. He was an ideal candidate, and Dr Favaloro did the CABG. As they say in Hollywood, the rest is history.

In the history of CABG, two earlier important advances must be recognized. In 1950, Dr Arthur Vineberg had earlier shown that you can cut an artery and bury it in the heart muscle, and this can help to bring blood to the heart muscle. Dr Gibbons’ role is also important as he invented the heart-lung machine. To operate on the heart, you need a clean and clear surgical field, with the heart stopped. To stop the pumping heart the blood circulation has to be diverted to a heart-lung machine, which will maintain the patient’s circulation, until the heart operation is completed. After the heart operation is completed, the heart lung machine is discontinued and the patient’s own circulation is re-established.

What then is CABG?

CABG is an operation to treat coronary artery disease (cholesterol blockages in heart arteries). Imagine that the artery is like a pipe, and there is a blockage in the pipe. The surgeon takes a vein from the leg, introduces it across the blockage and joins one end to the main artery of the body (aorta) and the other end to the diseased heart artery beyond the blockage. To allow the surgeon time to work, undisturbed by movement, the heart is stopped and the circulation of the body is diverted to a heart-lung machine which maintains the circulation, albeit at a lower level adequate to sustain life. Upon completion of the CABG, the heart is restarted, the heart-lung machine is slowly weaned off and the heart allowed to take over the circulation again. It may sound simple, but it is not. It is quite complicated and requires a team (the surgeon, the anesthetist and the perfusionist) effort. It also requires constant practice. That is why CABG success is also in some measure dependent on the team and the amount of CABG they perform weekly or monthly. Not all cardio-surgical team have the same success rate.

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