Arteries are blood vessels that carry oxygen-rich blood from the heart to various parts of the body, while veins carry oxygen-poor blood towards the heart for purification. Coronary arteries supply oxygen-rich blood to the heart muscles. Sometimes blood is unable to flow easily due to narrowing or blockages in these arteries. This condition is called coronary artery disease (CAD) and may be caused due to high blood pressure or high cholesterol deposits. In such cases, coronary artery bypass surgery (CABG) is performed to enable the free flow of blood.
CABG involves the grafting of a vein/artery from another part of the body to overcome or bypass over the obstruction in the affected coronary artery. The most commonly used blood vessels for CABG are the saphenous vein from the leg and the internal mammary artery from the chest. The formation of obstructions and failure of the saphenous vein graft over the long term has made the left internal mammary artery (LIMA) the preferred choice. The use of the left internal mammary artery restores 90% of the functionality of the heart and also maintains the same for the long term.
Left internal mammary artery surgery is performed under general anesthesia. The operation can be conducted through the open heart or minimally invasive procedures.
A long incision is made in the middle of your chest, and the breast bone is separated to gain access to the heart. A plastic tube is placed in the right atrium (upper chamber of the heart), and the blood is redirected to a heart and lung machine which will perform the function of the heart until the surgery is completed. The heart is then temporarily stopped.
Alternately, your surgeon may use a unique stabilising instrument to limit the beating of your heart at the required region, without entirely stopping the heart from pumping.
Three to four small incisions are made on the chest (instead of separating the breast bone) through which surgical instruments are inserted. Your surgeon may perform the surgery laparoscopically (fiber optic tube with a camera and a light source is added to guide your surgeon visually) or robotically-assisted (use of surgeon-controlled robotic arms).
With either of the methods, your surgeon makes a small opening in the coronary artery beyond the blockage. The left internal mammary artery is freed at one end from the chest and stitched to the opening of the coronary artery beyond the blockage to bypass the obstruction of blood flow. Unlike other grafts, the LIMA is not completely excised, but one end remains attached to the chest wall. Depending on the extent of blockage, you may require more than one bypass graft. When the bypass is completed, the grafts are checked, the breast bones are joined back with small wires (if the open technique was used), and chest incision(s) are closed.
This procedure takes about three to six hours to complete.
Plastic tubes are left in place to allow any drainage of excess blood from in and around the heart. The chest tubes are removed a day after the surgery. Your doctor will prescribe pain killers to relieve pain. You will be discharged from the hospital after about seven days and may recover completely in three months. It is essential to adopt a healthy lifestyle following recovery, which would include:
- Quitting smoking and moderating your alcohol intake
- Eating healthy food
- Maintaining a healthy weight
- Exercising regularly
- Risks and Complications
Complications associated with left internal mammary artery may consist of:
- Heart attack or stroke
- Irregular heartbeats
Advantages and disadvantages
The main advantage of using the left internal mammary artery is that it remains open and does not get clogged as easily as other grafts. Since it lies close to the left anterior descending coronary artery (LAD), the most important coronary artery of the heart, LIMA can be quickly exposed, separated from the chest wall and easily freed to bypass a blockage or narrowing. Other advantages include:
- Better survival
- Fewer reoperations
- Lower risk for a heart attack
- Less recurrence for angina (chest pain due to heart disease)
The left internal mammary artery also has limitations. This artery is sometimes too small to use and is very delicate, so much so that removal from the chest wall can damage the vessel wall, making it useless as a graft.