Coronary artery bypass surgery, also known as coronary artery bypass graft surgery, and colloquially heart bypass or bypass surgery, is a surgical procedure to restore normal blood flow to an obstructed coronary artery. A normal coronary artery transports blood to and from the heart muscle itself, not through the main circulatory system.
There are two main approaches. In one, the left internal thoracic artery (internal mammary artery) is diverted to the left anterior descending branch of the left coronary artery. In the other, a great saphenous vein is removed from a leg; one end is attached to the aorta or one of its major branches, and the other end is attached to the obstructed artery immediately after the obstruction to restore blood flow.
CABG is often indicated when coronary arteries have a 50 to 99 percent obstruction. The obstruction being bypassed is typically due to arteriosclerosis, atherosclerosis, or both. Arteriosclerosis is characterized by thickening, loss of elasticity, and calcification of the arterial wall, most often resulting in a generalized narrowing in the affected coronary artery. Atherosclerosis is characterized by yellowish plaques of cholesterol, lipids, and cellular debris deposited into the inner layer of the wall of a large or medium-sized coronary artery, most often resulting in a partial obstruction in the affected artery. Either condition can limit blood flow if it causes a cross-sectional narrowing of at least 50 percent.
CABG is the most common type of open-heart surgery. Doctors called cardiothoracic surgeons do this surgery.
However, CABG isn't the only treatment for CHD. Other treatment options include lifestyle changes, medicines, and a procedure called percutaneous coronary intervention(PCI), also known as coronary angioplasty.
PCI is a nonsurgical procedure that opens blocked or narrow coronary arteries. During PCI, a stent might be placed in a coronary artery to help keep it open. A stent is a small mesh tube that supports the inner artery wall.
CABG or PCI may be options if you have severe blockages in your large coronary arteries, especially if your heart's pumping action has already grown weak.
CABG also may be an option if you have blockages in the heart that can't be treated with PCI. In this situation, CABG may work better than other types of treatment.
The goals of CABG may include:
• Improving your quality of life and reducing angina and other CHD symptoms
• Allowing you to resume a more active lifestyle
• Improving the pumping action of your heart if it has been damaged by a heart attack
• Lowering the risk of a heart attack (in some patients, such as those who have diabetes)
• Improving your chance of survival
There are several types of coronary artery bypass grafting (CABG). Your doctor will recommend the best option for you based on your needs.
Traditional Coronary Artery Bypass Grafting
Traditional CABG is used when at least one major artery needs to be bypassed. During the surgery, the chest bone is opened to access the heart.
Medicines are given to stop the heart; a heart-lung bypass machine keeps blood and oxygen moving throughout the body during surgery. This allows the surgeon to operate on a still heart.
After surgery, blood flow to the heart is restored. Usually, the heart starts beating again on its own. Sometimes mild electric shocks are used to restart the heart.
Off-Pump Coronary Artery Bypass Grafting
This type of CABG is similar to traditional CABG because the chest bone is opened to access the heart. However, the heart isn't stopped, and a heart-lung bypass machine isn't used. Off-pump CABG sometimes is called beating heart bypass grafting.
Minimally Invasive Direct Coronary Artery Bypass Grafting
This type of surgery differs from traditional CABG because the chest bone isn't opened to reach the heart. Instead, several small cuts are made on the left side of the chest between the ribs. This type of surgery mainly is used to bypass blood vessels at the front of the heart.
Minimally invasive bypass grafting is a fairly new procedure. It isn't right for everyone, especially if more than one or two coronary arteries need to be bypassed.
Who Needs Coronary Artery Bypass Grafting?
Coronary artery bypass grafting (CABG) is used to treat people who have severe coronary heart disease (CHD) that could lead to a heart attack. CABG also might be used during or after a heart attack to treat blocked arteries.
Your doctor may recommend CABG if other treatments, such as lifestyle changes or medicines, haven't worked. He or she also may recommend CABG if you have severe blockages in your large coronary (heart) arteries, especially if your heart's pumping action has already grown weak.
CABG also might be a treatment option if you have blockages in your coronary arteries that can't be treated with percutaneous coronary intervention (PCI), also known as coronary angioplasty.
Your doctor will decide whether you're a candidate for CABG based on factors such as:
• The presence and severity of CHD symptoms
• The severity and location of blockages in your coronary arteries
• Your response to other treatments
• Your quality of life
• Any other medical problems you have
Physical Exam and Diagnostic Tests
To find out whether you're a candidate for CABG, your doctor will give you a physical exam. He or she will check your heart, lungs, and pulse.
Your doctor also may ask you about any symptoms you have, such as chest pain or shortness of breath. He or she will want to know how often and for how long your symptoms occur, as well as how severe they are.
Your doctor will recommend tests to find out which arteries are clogged, how much they're clogged, and whether you have any heart damage.
An EKG is a simple test that detects and records your heart's electrical activity. The test shows how fast the heart is beating and its rhythm (steady or irregular). An EKG also records the strength and timing of electrical signals as they pass through each part of the heart.
An EKG can show signs of heart damage due to CHD and signs of a previous or current heart attack.
Echocardiography (echo) uses sound waves to create a moving picture of your heart. The test shows the size and shape of your heart and how well your heart chambers and valves are working.
Echo also can show areas of poor blood flow to the heart, areas of heart muscle that aren't contracting normally, and previous injury to the heart muscle caused by poor blood flow.
There are several types of echo, including stress echo. This test is done both before and after a stress test. A stress echo usually is done to find out whether you have decreased blood flow to your heart, a sign of CHD.
Some heart problems are easier to diagnose when your heart is working hard and beating fast.
During stress testing, you exercise to make your heart work hard and beat fast while heart tests are done. If you can't exercise, you may be given medicine to raise your heart rate.
The heart tests done during stress testing may include nuclear heart scanning, echo, and positron emission tomography (PET) scanning of the heart.
Coronary Angiography and Cardiac Catheterization
Coronary angiography is a test that uses dye and special x rays to show the insides of your coronary arteries.
To get the dye into your coronary arteries, your doctor will use a procedure called cardiac catheterization
A thin, flexible tube called a catheter is put into a blood vessel in your arm, groin (upper thigh), or neck. The tube is threaded into your coronary arteries, and the dye is released into your bloodstream.
Special x rays are taken while the dye is flowing through the coronary arteries. The dye lets your doctor study blood flow through the heart and blood vessels. This helps your doctor find blockages that can cause a heart attack.
When deciding whether you're a candidate for CABG, your doctor also will consider your:
• History and past treatment of heart disease, including surgeries, procedures, and medicines
• History of other diseases and conditions
• Age and general health
• Family history of CHD, heart attack, or other heart diseases
Your doctor may recommend medicines and other medical procedures before CABG. For example, he or she may prescribe medicines to lower your cholesterol and blood pressure and improve blood flow through your coronary arteries.
PCI also might be tried. During this procedure, a thin, flexible tube with a balloon at its tip is threaded through a blood vessel to the narrow or blocked coronary artery.
Once in place, the balloon is inflated, pushing the plaque against the artery wall. This creates a wider path for blood to flow to the heart.
Sometimes a stent is placed in the artery during PCI. A stent is a small mesh tube that supports the inner artery wall.
What To Expect Before Coronary Artery Bypass Grafting
Tests may be done to prepare you for coronary artery bypass grafting (CABG). For example, you may have blood tests, an EKG (electrocardiogram),echocardiography, a chest x ray, cardiac catheterization, and coronary angiography.
Your doctor will give you specific instructions about how to prepare for surgery. He or she will advise you about what to eat or drink, what medicines to take, and what activities to stop (such as smoking). You'll likely be admitted to the hospital on the same day as the surgery.
If tests for coronary heart disease show that you have severe blockages in your coronary (heart) arteries, your doctor may admit you to the hospital right away. You may have CABG that day or the day after.
What To Expect During Coronary Artery Bypass Grafting
Coronary artery bypass grafting (CABG) requires a team of experts. A cardiothoracic surgeon does the surgery with support from an anesthesiologist, perfusionist (heart-lung bypass machine specialist), other surgeons, and nurses.
There are several types of CABG. They range from traditional surgery in which the chest is opened to reach the heart, to nontraditional surgery in which small incisions (cuts) are made to bypass the blocked or narrowed artery.
As with any type of surgery, coronary artery bypass grafting (CABG) has risks. The risks of CABG include:
• Wound infection and bleeding
• Reactions to anesthesia
• Stroke, heart attack, or even death
Some patients have a fever associated with chest pain, irritability, and decreased appetite. This is due to inflammation involving the lung and heart sac.
This complication sometimes occurs after surgeries that involve cutting through the pericardium (the outer covering of the heart). The problem usually is mild, but some patients may develop fluid buildup around the heart that requires treatment.
Memory loss and other issues, such as problems concentrating or thinking clearly, might occur in some people.
These problems are more likely to affect older patients and women. These issues often improve within 6–12 months of surgery.
In general, the risk of complications is higher if CABG is done in an emergency situation (for example, during a heart attack). The risk also is higher if you have other diseases or conditions, such as diabetes, kidney disease, lung disease, or peripheral arterial disease (P.A.D.).