Dr Tapas Ray Chaudhury
Cardiothoracic Surgeon
LIMA : RIMA Bypass
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Whoever, seen a patient undergone a bypass must have noticed a cut in their legs, from where we have taken out a portion of their spare leg vein to use as a tube to make new blood to flow to their heart bypassing the blockages, just like a flyover. In addition we also use an artery from inside the chest wall, called LIMA, for longer period of remission.
However, in follow up we have noticed that the leg veins are getting blocked by 10 to 12 years, but the LIMA is still working well. This happens because of pressure difference between an artery and a vein. Use of an artery appeared to be a necessary surgical step.
​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 above). 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.
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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 10 to 12 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). Where as inside leg veins the mean pressure is only around 7 to 10 mm of mercury!
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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 (middle pic). 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 (last pic). Most of the patients with both (Bilateral) LIMA and RIMA remain trouble free for more than 20 years, and often up to 25 years, where as a Stent lasts upto 10 years at the most. Multiple Stents last even less!
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