A bypass is a surgical procedure that reroutes blood flow around a blocked artery. The surgeon takes a healthy blood vessel from another part of your body and attaches it above and below the blockage, creating a detour so blood can reach its destination. The term most often refers to coronary artery bypass grafting (CABG), a heart surgery performed when one or more arteries supplying the heart muscle become severely narrowed or blocked by fatty buildup. Bypass surgery can also be performed on blocked arteries in the legs.
How a Heart Bypass Works
Your heart muscle needs a constant supply of oxygen-rich blood, delivered through coronary arteries. Over time, fatty deposits can build up inside these arteries and narrow them, reducing blood flow. When the narrowing becomes severe enough, it starves the heart muscle of oxygen, causing chest pain and raising the risk of a heart attack.
During bypass surgery, a surgeon harvests a healthy blood vessel from your chest, leg, or arm. They open the chest through the breastbone, then sew one end of the harvested vessel to the large artery leaving the heart (the aorta) and the other end to the coronary artery below the blockage. Blood now flows through this new route, “bypassing” the clogged section entirely. If multiple arteries are blocked, the surgeon creates multiple grafts in the same operation, which is where terms like “double bypass,” “triple bypass,” or “quadruple bypass” come from.
When Bypass Surgery Is Recommended
Not every blocked artery requires bypass surgery. Doctors typically recommend it for the most serious patterns of blockage, where the survival benefit is clearest. According to American Heart Association and American College of Cardiology guidelines, the strongest reasons include a blockage greater than 50% in the left main coronary artery (the vessel that feeds the largest portion of the heart), blockages of 70% or more in two major branches simultaneously, or disease affecting all three major coronary arteries.
Other situations that call for bypass include two-vessel disease combined with a weakened heart, chest pain that persists despite maximum medication, or ongoing loss of blood flow that hasn’t responded to less invasive treatments like stents. For patients with complex, widespread disease, bypass surgery has been shown to reduce the risk of future heart attacks more effectively than stenting, and in some cases it provides a clear survival advantage. A large trial called SYNTAX found that patients with triple-vessel disease who received stents had a 40% higher mortality rate on extended follow-up compared with those who had bypass surgery.
Where the Graft Vessels Come From
The blood vessel used for the bypass, called a graft or conduit, can come from several places in your body. The most common sources are an artery running along the inside of the chest wall (the internal mammary artery), a vein from the leg (the saphenous vein), or an artery from the forearm (the radial artery).
The left internal mammary artery is the preferred choice, especially for bypassing the most critical vessel on the heart. It has the best long-term track record: more than 90% of these grafts remain open after 10 years. Radial artery grafts from the forearm stay open about 79% of the time at 10 years, while leg vein grafts have a patency rate around 74% over the same period. Current guidelines recommend using an artery graft over a vein graft whenever possible because arteries hold up better over time and are associated with fewer complications down the road. When multiple grafts are needed, surgeons often use a combination of arterial and vein grafts.
On-Pump vs. Off-Pump Surgery
There are two main approaches. In traditional “on-pump” bypass, the surgeon temporarily stops the heart and connects the patient to a heart-lung machine that circulates blood and delivers oxygen while the heart is still. This gives the surgeon a motionless field to work on and tends to allow more complete grafting, especially when many vessels need to be bypassed.
In “off-pump” or “beating heart” bypass, the surgeon operates on the heart while it’s still pumping, using a stabilizing device to hold the small area being grafted steady. This approach avoids the heart-lung machine, which reduces the overall length of surgery. Off-pump bypass is associated with lower rates of certain complications, particularly inflammation and tiny blood clots reaching the brain. However, it’s technically more demanding and isn’t suitable for every patient. Your surgical team will choose the approach based on how many grafts you need and your overall health.
What Recovery Looks Like
After surgery, you’ll spend a day or two in the intensive care unit before moving to a regular hospital room. Most people stay in the hospital for about a week total. Full recovery takes 6 to 12 weeks, though patients who have minimally invasive bypass need less time.
During those first weeks at home, common side effects include chest pain around the incision, muscle tightness in the shoulders and upper back, fatigue, trouble sleeping, mood swings, and swelling where vessels were harvested. These typically resolve within four to six weeks. You’ll gradually increase your activity level, often starting with short walks and building from there. Many hospitals refer patients to a cardiac rehabilitation program, which provides supervised exercise and guidance on diet and lifestyle changes.
Long-Term Outlook
Bypass surgery relieves chest pain for most patients and restores blood flow to the heart muscle, which improves heart function and energy levels. One long-term study tracking patients for an average of nearly 12 years after surgery found that about 68% were still alive, though this included patients who already had significant heart disease and weakened hearts before their operations.
The longevity of your results depends heavily on the type of graft used and how well you manage risk factors afterward. Arterial grafts from the chest wall last the longest. Vein grafts from the leg can gradually narrow over the years, and some patients eventually need additional procedures. Controlling blood pressure, cholesterol, and blood sugar, staying physically active, and not smoking all help keep grafts open longer and slow the progression of new blockages elsewhere in the arteries.
Bypass for Blocked Leg Arteries
Bypass surgery isn’t limited to the heart. People with peripheral artery disease, where fatty deposits block arteries in the legs, can develop pain while walking, sores that won’t heal, or in severe cases, tissue death. When medications and less invasive treatments fail, a vascular surgeon can perform a peripheral artery bypass. The concept is the same: a graft vessel is sewn in above and below the blockage to restore blood flow. The surgeon makes incisions of about 4 to 8 inches above and below the blocked section, and the graft is typically a vein taken from elsewhere in the body. Recovery is generally shorter than for heart bypass, since the chest isn’t opened.