Bio-Mechanical Analysis and Sourcing of Vascular Conduits
The durability of a bypass operation is determined almost entirely by the biological and mechanical properties of the conduits used. A conduit must be able to withstand the high-pressure environment of the arterial system while resisting the inflammatory processes that lead to atherosclerosis.
The Left Internal Mammary Artery (LIMA) is physiologically unique. It is an "elastic" artery that produces high levels of nitric oxide, a natural vasodilator that prevents blood clots and inhibits the growth of plaque. Because it remains attached to its original source of blood (the subclavian artery), it is a "pedicled" graft. Its 20-year patency rate is unparalleled in surgery, often exceeding 90%. Surgeons almost always use the LIMA to bypass the Left Anterior Descending (LAD) artery, which is the most critical vessel in the heart.
When multiple bypasses are required, surgeons turn to the Great Saphenous Vein from the leg or the Radial Artery from the arm. Vein grafts are "free grafts," meaning they are detached at both ends. While veins are easier to harvest and handle, they are structurally designed for a low-pressure system. When moved to the high-pressure arterial system, they undergo "intimal hyperplasia," a thickening of the vessel wall that can lead to closure within 10 to 15 years. To mitigate this, many surgeons now utilize "no-touch" harvesting techniques, preserving the surrounding tissue of the vein to maintain its structural integrity and longevity.