Dr. Tapas Raychaudhury
LIMA : RIMA Bypass
Previously the veins from the legs were used as a conduit for bypass. Soon it was found out that longevity of leg veins were not more than 7 to 10 years. They slowly degenerate as veins are not used to the high pressure present inside a human coronary circulation (mean pressure of 95 mm of mercury).
It became apparent that for a longer durability one needs to use an artery which is used to the same pressure to that of coronary circulation. So from early eighty one of the two ‘Internal Mammary Arteries’ ( or ‘Internal Thoracic artery’ as said in USA) was selected as the choice of conduit(See Gallery below). Both the arteries run along the breast bone just in front of the heart and are very suitable to swing it to the heart. The left artery (LIMA) was then grafted to the main coronary artery called LAD (Left anterior descending artery) and leg veins are then used for the lesser important coronary arteries. Till date this configuration remains the most popular bypass. However, as the post-operative data kept mounting, it became apparent that patients are coming back with blocked venous grafts while their LIMA is still functioning well. This prompted many surgeons, including me, to switch over to ‘Total arterial grafting’ using both the Left (LIMA) and the Right (RIMA) internal mammary arteries.
In smaller hearts LIMA and RIMA can be joined as an inverted Y and are used to wrap round the heart supplying the all coronary arteries, in front as well as to the back of the heart. However, in a very large heart they are used separately to the two most important coronary arteries and the rest of the blocked vessels are bypassed using veins or an artery from the forearm (see Gallery). Most of the patients with both (Bilateral) LIMA and RIMA remain trouble free for more than 15 years, and often up to 25 years.
Beating Heart Bypass Surgery
In bypass surgery usually one tube, it may be artery or vein, is joined with patient’s blocked
coronary artery using intricate stitching method. Usually the diameter of a target coronary
artery at the site of joining (anastomosis) is approximately 2 mm.Consequently, the site of
anastomosis should be motionless. Before 1996, it was achieved by putting the heart under
Heart-Lung machine support and heart was made to stop by using chemical solution. The
grafting then used to be performed on a still, motionless heart. However, soon it became
apparent that use of heart lung machine and stopping the heart for a long time had certain
complications resulting in more kidney failure, more heart failure and infection.
During 1995 surgeons in Belgium, Italy as well as in India started using Beating Heart Bypass,
where Heart lung machine was not used and the area of anastomosis was kept stable by
using multiple stay sutures with traction. However, the method was tedious but the harmful
effect of heart-lung machine could be avoided. Owing to the complex technique of manual
stabilization, this technique did not get wide spread popularity amongst the heart surgeons.
A breakthrough came in 1998, when a mechanical stabilizer (See Gallery Above) was first
introduced in clinical application. This device fits into the chest spreader, has a flexible arm
which becomes rigid when the regulator is tightened. At the tip there is U shaped suction device which sits on either side of the target coronary artery, thus making the target area motion less while rest of the heart keeps pumping blood to the body in usual way (see picture). Now in our unit nearly 99% of all bypass surgeries are done using this ‘Beating heart’ technique(See video).