The internal mammary vein, also known as the internal thoracic vein, is a significant blood vessel within the human chest. It plays an important role in the body’s natural circulatory system.
The internal mammary vein refers to the vessels that accompany the internal mammary artery. While both are integral to chest circulation, their roles differ, with the vein primarily involved in blood drainage.
Locating and Understanding the Internal Mammary Vein
The internal mammary vein is located deep within the chest, running alongside the sternum, or breastbone. There are two internal mammary veins, one on each side of the body, closely accompanying the internal mammary artery. These veins begin from the superior epigastric vein, which drains blood from the abdominal wall.
As they ascend, these veins collect deoxygenated blood from various structures in the chest wall, including the intercostal spaces and the breasts. The internal mammary veins then drain this blood into larger veins in the upper chest, specifically the brachiocephalic veins, which ultimately return it to the heart for reoxygenation.
Why It Excels in Bypass Surgery
While the term “internal mammary vein” might suggest its use, it is the internal mammary artery (IMA), also called the internal thoracic artery, that is primarily used in coronary artery bypass grafting (CABG) due to its superior long-term performance. This artery possesses unique biological and anatomical characteristics that make it an exceptional choice for creating new pathways around blocked coronary arteries.
One key property is its natural resistance to atherosclerosis, which is the hardening and narrowing of arteries due to plaque buildup. Unlike many other vessels, the IMA is less susceptible to these changes, ensuring it remains open and functional for an extended period. Its inner lining, the endothelium, exhibits remarkable health and resilience, promoting smooth blood flow and reducing the risk of clot formation. This is partly due to its ability to produce higher levels of nitric oxide, a substance that helps blood vessels widen and prevents spasms.
The internal mammary artery also has a muscular layer that allows it to adapt effectively to the higher pressures of the arterial system when used as a graft. Furthermore, its anatomical proximity to the heart simplifies the surgical procedure, allowing for shorter graft lengths and minimizing surgical complexity.
The Surgical Advantage and Patient Impact
The unique properties of the internal mammary artery translate into substantial advantages in cardiac surgery, particularly in improving patient outcomes. Grafts created from this artery demonstrate remarkably high long-term patency rates. Studies show that approximately 85% to 95% of internal mammary artery grafts remain free of significant narrowing or blockage at 7 to 10 years, a significantly better rate compared to vein grafts.
Due to this exceptional durability, patients who receive internal mammary artery grafts experience a reduced need for repeat bypass surgeries or other cardiovascular interventions in the future. This long-lasting effectiveness avoids additional procedures, which can be burdensome and carry their own risks.
The use of the internal mammary artery has revolutionized CABG, leading to improved patient prognosis and survival rates. Patients receiving these grafts often have better long-term survival compared to those receiving other types of grafts. Its proven clinical benefits and survival advantages have firmly established the internal mammary artery as the “gold standard” for coronary artery bypass grafting.