LIMA stands for Left Internal Mammary Artery, a blood vessel that runs along the inside of your chest wall. In cardiology, it’s best known as the gold standard graft used in coronary artery bypass surgery (CABG) to reroute blood around a blocked heart artery. When someone mentions LIMA, they’re almost always talking about this surgical context: a surgeon detaches one end of the artery from its normal position and connects it directly to a coronary artery, restoring blood flow to the heart muscle.
Where the LIMA Sits in Your Body
The left internal mammary artery branches off the left subclavian artery, which itself comes directly from the aortic arch, your body’s main blood highway. From there, it travels downward along the inner surface of the front chest wall, running about 1 to 2 centimeters to the left of the breastbone. Along the way, it sends smaller branches out to supply the chest wall, sternum, and surrounding tissues.
Its location is what makes it so useful for heart surgery. The LIMA sits close to the heart and is long enough to reach the left anterior descending artery (LAD), the coronary artery that supplies the largest portion of the heart’s muscle. A surgeon can redirect the LIMA’s lower end and sew it directly onto the LAD below the blockage, essentially giving the heart a new supply line without needing a completely separate piece of vessel.
Why Surgeons Prefer It Over Vein Grafts
The LIMA has a remarkable resistance to atherosclerosis, the fatty plaque buildup that clogs arteries in the first place. This comes down to its biology. The inner lining of the LIMA has fewer gaps between cells compared to veins typically used in bypass surgery, which makes it harder for cholesterol-carrying particles to seep into the vessel wall and start forming plaque. The artery also produces high levels of nitric oxide, a molecule that keeps blood vessels relaxed and discourages clot formation. On top of that, the LIMA’s lining is rich in natural anti-clotting substances.
These properties translate into dramatically better long-term results. LIMA grafts remain open in about 95 to 96% of patients at 10 years. Saphenous vein grafts, taken from the leg, deteriorate much faster. Roughly 10% of patients with vein grafts need a repeat procedure within a decade because the graft has failed. That gap in durability is why the LIMA-to-LAD connection became the standard approach worldwide.
How the LIMA Is Used in Bypass Surgery
In a typical CABG procedure, the surgeon frees the LIMA from the chest wall while keeping its origin at the subclavian artery intact. The lower end is then sewn onto the LAD artery beyond the point of blockage. Because the LIMA stays connected to its original blood supply at one end, blood flows naturally from the aorta through the subclavian artery, down the LIMA, and into the coronary artery. This “pedicled” approach preserves the artery’s surrounding tissue and blood supply.
There are two main harvesting techniques. The traditional pedicled method takes the artery along with a strip of surrounding tissue, fat, and veins. The skeletonized method isolates just the artery itself. Skeletonized harvesting yields a longer usable segment and cuts the risk of sternal wound infection by more than half, which matters especially for patients with diabetes or obesity. Both techniques produce excellent long-term graft function.
Using Both Mammary Arteries
You have two internal mammary arteries, one on each side of the breastbone. Some surgeons advocate using both (called bilateral internal mammary artery grafting, or BIMA) to supply multiple coronary arteries with arterial conduits rather than relying on vein grafts for the additional bypasses.
Observational data from a study of nearly 48,000 bypass patients followed for an average of 12 years found that those who received both mammary arteries had a 30% lower mortality rate and a lower rate of repeat procedures (15% versus 19%) compared to those who received only the left. However, the largest randomized trial on the question, the Arterial Revascularization Trial involving over 3,100 patients across seven countries, found no significant survival difference at five years. Death rates were 8.7% in the bilateral group and 8.4% in the single group, a statistically meaningless gap. The debate continues, and the choice often depends on a patient’s individual risk profile and the surgeon’s experience.
Recovery After LIMA Harvesting
Because the LIMA is detached from the chest wall during surgery, recovery involves standard sternal precautions to let the breastbone heal. For the first four to six weeks, you’ll typically be told to avoid lifting anything heavier than 5 to 10 pounds and to avoid raising your arms above shoulder level. Reaching behind your body and pushing yourself up from a chair using your arms are also restricted during this window. By six to eight weeks, the weight limit gradually increases to about 20 pounds, and most patients return to normal daily activities within two to three months.
One uncommon but recognized risk of mammary artery harvesting is injury to the phrenic nerve, which controls the diaphragm. This occurs in roughly 4% of cases when the right internal mammary artery is harvested high up, and it can cause temporary breathing difficulty. About two-thirds of affected patients recover on their own without further intervention. The left side carries a lower risk because the nerve’s anatomy is slightly different, but surgeons still take care to protect it during the dissection.
What Makes the LAD Connection So Important
The LAD is sometimes called the “widow maker” because blockages in this artery can cause massive heart attacks. It feeds the front wall and a large part of the left ventricle, the chamber responsible for pumping blood to the entire body. Connecting the LIMA specifically to this artery pairs the most durable graft with the most critical target. Studies consistently show that patients who receive a LIMA-to-LAD graft live longer and have fewer cardiac events than those who receive vein grafts to the same artery. This single surgical connection has become so central to modern heart surgery that LIMA usage rates are tracked as a quality measure in cardiac surgery programs.