Overview of Saphenous Vein Grafts
Coronary artery disease (CAD) is a widespread condition that affects many. It is known to affect about 15.5 million individuals aged 20 or older in the United States according to a 2016 report from the American Heart Association (AHA). The disease affects the blood vessels of the heart and can be managed in various ways. These include changes in lifestyle, the use of medication, or through a process called coronary revascularization. This last option is a surgical technique that helps restore blood flow to the heart.
In 1960, Dr. Robert H. Goetz was the first to perform coronary revascularization. He connected an artery from the chest (the right internal mammary artery, or RIMA) to a blood vessel in the heart (the right coronary artery). Then in 1967, Dr. René Favaloro described a new method that involved the use of a vein from the leg (the greater saphenous vein, or GSV) to bypass damaged blood vessels in the heart. The GSV was the preferred choice for this procedure because it is easy to reach and has considerable length.
However, in 1986, medical studies showed that another chest artery, known as the left internal mammary artery (LIMA), was superior for restoring blood flow specifically to the left anterior descending artery (LAD) in the heart. The LIMA bypass resulted in greater patient survival rates and proved more efficient than the GSV bypass. Since then, it has become the preferred vessel for coronary artery bypass grafting (CABG).
However, the LIMA may not be suitable for all patients and there might be a need for additional vessels. For example, to bypass other blocked segments when LIMA is deemed unusable, the original method of using the saphenous vein grafts may still be used. Despite advances in treating CAD, saphenous vein grafts remain important options for heart bypass surgeries, especially in cases where multiple blocked vessels need to be treated or single vessel disease where LIMA is found to be unfit for use.
Anatomy and Physiology of Saphenous Vein Grafts
The saphenous vein graft (SVG) involves either the great saphenous vein (GSV) or the small saphenous vein (SSV). Mostly, the GSV is used in these grafts, but in some cases, the SSV could also be a good choice.
The GSV is a visible vein on the surface of the lower leg that drains into a vein called the common femoral vein. This vein starts near the inside of the ankle, crosses over the shin bone (tibia), and then goes up along the inside of the knee and thigh before heading towards the groin. It takes in blood from other veins, including some accessory saphenous veins, and enters a space called the fossa ovalis, which is around 4 cm below and to the side of the pubic bone. Here, it joins with several other veins to form the saphenofemoral junction on the front of the common femoral vein.
On the other hand, the SSV starts where the outside veins of the foot’s dorsal network meet, moves behind the outside of the ankle, and then goes up in the calf’s subcutaneous tissue (the layer of fat and connective tissue underneath the skin). After going through the calf, it pierces a layer of connective tissue called the fascia lata and empties into the vein in the knee pit called the popliteal vein. While it makes its way upwards, it connects with the GSV and the deep vein system via numerous branches that pierce other layers of tissue.
Why do People Need Saphenous Vein Grafts
The saphenous veins are important for treating coronary artery disease, a condition that affects the heart’s blood vessels. The American College of Cardiology and the American Heart Association have guidelines on when it’s appropriate to use these veins for a procedure called coronary artery bypass grafting. This procedure improves blood flow to the heart when the arteries are blocked or damaged.
When it comes to treating coronary artery disease, left internal mammary artery (LIMA) is generally seen as the go-to. This is because it tends to stay open for longer, improving the patient’s outcomes. Saphenous vein grafts, which are veins located in your leg, have historically been used in addition to LIMA or when LIMA was not available. However, recent data says that the radial artery (an artery in your arm) is a better choice than saphenous veins due to increased patency, which means it stays open and functionally for longer. Therefore, saphenous vein grafts are currently suggested as backups to LIMA when radial artery grafts are not suitable.
These veins, named the greater saphenous vein (GSV) and the lesser saphenous vein, have other uses too. They are often used for bypass surgeries in the lower part of the body. For instance, a saphenous vein can be moved and used for a procedure that goes from the femoral artery in the thigh to the popliteal artery in the knee which treats occluded, or blocked, vessels when conservative treatment or a procedure called angioplasty aren’t suitable. These veins can also be used to increase the length of the vascular pedicle – a stem of tissue that contains nerves and blood vessels – in free tissue transfer reconstruction, a type of surgery that is especially useful for the head and neck.
When a Person Should Avoid Saphenous Vein Grafts
There are several reasons why a saphenous vein graft, a procedure that uses one of your veins in your leg, may not be an option for some people:
The health and quality of the saphenous vein itself can affect whether it’s suitable for a graft. For example, if a person has local skin infection or blood clotting in the veins (cellulitis/thrombophlebitis) or recent blood clot formation (venous thrombosis), the vein may be in poor condition for a graft. Also, previous procedures involving the vein, like having it stripped or manipulated, could make the vein unable to be used in the graft.
Other physical characteristics of the vein can also interfere with the success of the graft. If the vein branches too much, has varicose veins (swollen, twisted veins), a thick wall, or a small diameter, these factors could increase the chance that the graft will fail.
Equipment used for Saphenous Vein Grafts
When a doctor performs a procedure called a saphenous vein grafting, the kind of equipment they need depends on the type of method they use. The two primary techniques are open vein harvest (OVH) and endoscopic vein harvest (EVH).
The open vein harvest requires a set of general surgical tools that are commonly used in any operations involving the blood vessels. If the exact location for the procedure is uncertain, an ultrasound machine can be used to guide the surgeon, avoiding cuts and dissections that aren’t needed. The surgeon will also utilize non-dissolving and single-thread sutures, and small surgical clips to tie off any branching veins. To clean and prepare the vein for grafting, a solution of saline (medical-grade saltwater) that’s been mixed with a drug called heparin, and a tube that can be inserted into the vein, are also necessary.
On the other hand, an endoscopic vein harvest requires several additional tools on top of the standard surgical ones already mentioned. These extra tools include a machine that pumps carbon dioxide gas into the vein (which helps widen it for easier viewing and surgery), a special tool that has a balloon at the end and a camera for a more detailed visual inspection inside the vein, a conical dissector tool, and an instrument that utilizes two electrical charges to help stop bleeding by sealing the blood vessels (a process known as endoscopic hemostasis).
Who is needed to perform Saphenous Vein Grafts?
The process to extract and use the saphenous vein, a major vein in the leg, involves the skills and experience of several trained medical professionals. First, a surgeon is required to remove the vein carefully, ensuring it remains undamaged. This part of the procedure is critical because any harm to the vein can impact the success of the further steps.
Next, a cardiothoracic surgeon, a doctor specializing in surgeries of the heart and chest, is involved. Their role is to connect the extracted vein to the aorta — the large blood vessel that distributes blood from your heart to the rest of your body — and then to the appropriate arterial area.
When there is a need to bypass a part of your circulatory system (which carries blood throughout your body) using a graft like this, a vascular surgeon is usually the one who performs the procedure. A vascular surgeon specializes in treating medical conditions involving blood vessels.
Preparing for Saphenous Vein Grafts
Medical images aren’t traditionally needed for the procedure of harvesting a saphenous vein graft (SVG), which is a type of heart bypass surgery. However, these images can now be used to help reduce any complications that might happen from dissecting too much tissue or from errors in the surgery.
Traditionally, surgeons would use physical landmarks in the body to identify and dissect the Great Saphenous Vein (GSV) or the Small Saphenous Vein (SSV). The veins in both limbs would be available for dissection until the surgeon finds a suitable vein segment. Lately, tools like ultrasonography, which uses sound waves to create images of blood flowing through the arteries and veins, have been used. Pre-operative vein mapping, which is a non-invasive method to visualize the veins, has also proved useful.
By using these imaging techniques, doctors can find suitable vein segments for the surgery without exposing and dissecting unnecessary veins. This can help reduce the likelihood of complications during the surgery.
How is Saphenous Vein Grafts performed
The saphenous vein, which runs along the length of your leg, can be used in a procedure called coronary artery bypass grafting. This procedure helps to improve blood flow to the heart. Doctors typically use one of two methods to collect this vein: it can either be reversed (which means it will no longer have the function of controlling blood flow), or it can be valvotomized (which means the valves are removed).
The doctors can find the saphenous vein either by feeling the pulse in your leg and following its path, or by using an ultrasound machine to get a direct look at the vein.
There are two methods for collecting the vein: the open method and the endoscopic method.
In the open method, doctors make a cut along the vein path. This method has been used for many years. They carefully move along the vein, taking care to handle it as gently as possible to avoid any damage. Any smaller branches from the vein are found and sealed off. When they have enough of the vein, they clamp off the ends, cut it, and remove it. They then fill the vein with a special solution to look for any leaks that might need to be fixed. The vein is kept in this solution until it’s used in the bypass graft.
In the endoscopic method, doctors use a special tool with a camera to see and gather the vein. They make a small cut just above the knee, typically gathering about 35 cm of the vein. Or, they can make another small cut higher up on the leg, if they need a longer piece. A balloon-like tool is inserted at the cut and is inflated to create space around the vein. Other tools are used to cut and seal off any branches from the vein. Once the entire vein is free, another cut is made at the upper thigh, and the vein is removed. Just like in the open method, any leaks are fixed, and the vein is stored in a special solution until it’s used in the bypass graft.
In both methods, it’s important for the doctors to handle the vein very carefully. Any damage to the vein can lead to blood clots and reduce the success of the bypass graft.
Possible Complications of Saphenous Vein Grafts
The two main complications that can occur with vein grafting during coronary artery bypass graft surgery (CABG) are thrombosis (formation of blood clots) and atherosclerosis (hardening and narrowing of the arteries). Both of these complications can reduce how long the graft is effective. In fact, the graft can fail, not work as expected, in 10-25% of patients within 12-18 months after the surgery, with the failure rate increasing by 5% each year after five years.
Early graft failure, up to 18 months after the procedure, is believed to result from an overgrowth of the inner lining of the artery (intimal hyperplasia), due to injury to the artery lining, reduced formation of nitric oxide (a substance that helps blood vessels widen), increased formation of blood clots, secretion of growth factors, inflammation, and build-up of certain types of cells. These issues could be associated with more handling and trauma to the vessel during the procedure.
Late graft failure, happening more than 18 months after the surgery, occurs as the overgrowth in the artery lining leads to the formation of plaque akin to atherosclerosis, which can obstruct the artery.
Beyond worries about how long the graft will last, there can be other complications related to the vein harvest procedure itself. These include ongoing pain or abnormal sensations after surgery, infections at the surgical site, development of varicose veins or swelling in the lower leg due to reduced blood flow out of the leg after removal of the vein. The traditional open vein harvest may result in increased pain post-surgery and persistent abnormal sensations due to the length of the incision and accidental nerve injury during the procedure. These patients also have an increased risk of surgical site infections due to the longer incision.
While the endoscopic vein harvest reduces the risk of many of these complications compared to the open technique, some argue that it can cause more trauma to the vessel during the procedure, which might increase the risk of graft failure after the surgery. However, recent large-scale studies suggest that may not be the case.
What Else Should I Know About Saphenous Vein Grafts?
The saphenous vein was typically the first choice for a procedure known as coronary artery bypass grafting, which is a surgery that improves blood flow to the heart. However, due to a high failure rate, mix of other vessels (such as the Left Internal Mammary Artery (LIMA), Radial Artery (RA), and increasingly the Right Internal Mammary Artery (RIMA)) are now being used more often for these bypass grafts.
Additional vessels, like the gastroepiploic artery (an artery in the stomach region), are also being studied for use, but so far they haven’t shown clear advantages over using the saphenous vein, and thus are used less often.
Switching from vein to artery grafts is due to the adaptability of arteries. They respond better to their new role as coronary bypass grafts. Arterial grafts show less likelihood of hyperplasia (where cells increase in volume – a condition that can lead to health issues) and are more resistant to conditions that can lead to failure, such as thrombosis (blood clots) and atherosclerosis (hardening of the arteries). After the bypass operation, lifestyle changes, antiplatelet drugs (which prevent clot formation), and sometimes additional procedures may be needed to keep the graft healthy and effective.
Even though arteries have advantages, the saphenous vein still plays a crucial role because surgeons are familiar with it and understand how it behaves after grafting. It is also relatively easy to harvest (remove from the body for use in another area), and there is ample length available. The LIMA remains the popular choice for this type of surgery, but the saphenous vein continues to be an important tool for surgeons performing heart bypass operations.