Purpose of Heart Bypass Surgery

Heart bypass surgery (also called bypass surgery, coronary artery bypass graft, or coronary artery bypass graft CABG) is performed as a surgical intervention to address blockages in the native coronary arteries. When bypass surgery is required, these arteries have become blocked or partially blocked due to disease. Usually, a blockage (or partial blockage) is caused by coronary artery disease (CAD).

Heart bypass surgery involves taking healthy arteries from somewhere in the body (usually from the leg, arm, or chest area), then connecting this graft artery, thereby making a new passageway for blood (and oxygen) to flow. The overall goal of the procedure is to bypass the blockage in the existing, diseased coronary artery.

Diagnoses Related to Heart Bypass Surgery

There are several conditions that are treated by performing heart bypass surgery, these include angina and coronary artery disease.


Angina is a condition that is caused by decreased blood flow to the heart. It is characterized by chest pain or chest pressure, often described as “crushing or squeezing” pain.

Angina is usually brought on by physical exertion, however, there is a type of angina, called unstable angina, which often occurs when a person is at rest. Unstable angina is associated with a risk of myocardial infarction (heart attack).

The New York Heart Association identified several stages of angina, including:

  • Class I: Symptoms occur during unusually strenuous activity
  • Class II: Mild shortness of breath and/or chest pain and slight limitation during ordinary activity
  • Class III: Symptoms during physical exertion, marked limitation during activities such as walking short distances, comfortable only at rest
  • Class IV: Symptoms occur while one is at rest, severe limitation in activities, usually involves people who are on bedrest

Unstable angina is an emergency situation that could indicate a person is having a heart attack. It’s important to seek immediate medical care (such as calling 911) if you have symptoms of unstable angina.

Symptoms of a heart attack include:

  • Chest pain, pressure, or an unusual feeling in the chest, back, neck, jaw, or upper abdomen, or on one or both shoulders/arms.
  • Shortness of breath
  • Sweating
  • Nausea or vomiting
  • Lightheadedness
  • Sudden weakness
  • A fast or irregular heartbeat

Coronary Artery Disease

Coronary artery disease is a condition that is caused by atherosclerosis (historically called hardening of the arteries) that can, over time, constrict or occlude the blood flow through the blood vessels. When atherosclerosis occurs in the blood vessels that supply blood and oxygen to the heart muscle, this is called coronary artery disease.

The underlying cause of atherosclerosis is plaque, a fatty, waxy substance (comprised partially of cholesterol calcium, and other substances found in the blood.) which forms deposits in the artery wall.

To decide whether heart bypass surgery is the best option for a person, the physician must assess the condition of your heart and blood vessels (including the coronary arteries), by evaluating your cardiovascular system.

Signs and symptoms (such as shortness of breath, chest pain, lightheadedness, and fatigue) will be evaluated, and you will be asked about the severity, length, and frequency of these symptoms, during a history and physical examination. In addition, various tests will be performed to find out if you meet the medical criteria for having bypass surgery.

The tests include those that measure the extent of the blockage/s in your arteries as well as evaluating any heart damage that has occurred. In addition to tests that help the healthcare provider decide if you are a candidate for bypass surgery, other tests will be performed to ensure that you are healthy enough to undergo the surgery.

Coronary Artery Disease Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

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Less Invasive Treatment

Heart bypass surgery is usually an elective procedure aimed at decreasing the risk of a myocardial infarction (heart attack) and decreasing the intensity and incidence of pain (such as angina). But this does not mean a person can simply choose to have heart bypass surgery, you must first qualify by having the specific pre-established criteria (explained below).

There are, however, instances where an emergency heart bypass surgery is performed (such as after a person has a heart attack).

For those who have limited success from lifestyle changes, medication and less invasive treatment modalities, a heart bypass is a feasible option. One such treatment is angioplasty, involving the insertion of a very small balloon that is inflated to help widen the lumen (opening) of the artery.

Less invasive types of treatment (other than bypass surgery) may involve:

  • Diet: Losing weight, eating a low fat, heart-healthy diet
  • Lifestyle changes: Like quitting smoking and exercising regularly
  • Medication: Such as nitroglycerin tablets, sprays, and patches to improve blood flow and decrease pain such as in angina, or statins or other medications that lower blood cholesterol levels to help slow the progression of CAD


Medical criteria are specific indicators (including signs and symptoms, lab tests, and other factors, such as the frequency or severity of symptoms) in which a type of treatment or surgery is recommended. Conditions that meet the criteria for having heart bypass surgery include:

  • Disabling angina that does not respond to maximum noninvasive treatment (such as medication) when surgery can be performed with acceptable risk
  • Disease that is present in more than one coronary artery, in addition to a malfunctioning left ventricle (the heart’s primary pumping chamber)
  • Severe stenosis (narrowing) of the left main coronary artery (the artery that supplies most of the blood to the left ventricle of the heart)
  • Stenosis of 70% of two coronary arteries (called the LAD and the proximal left circumflex arteries)
  • An extreme form of coronary artery disease involving three of the major coronary arteries (called three-vessel disease).
  • Blockage of a coronary artery that cannot be successfully treated with a less invasive procedure called an angioplasty
  • Unsuccessful results from a previous angioplasty or stent placement (a small wire mesh tube to hold the artery open)
  • Recurrence of narrowing of the artery, after a previous angioplasty or stent placement
  • Myocardial infarction (heart attack) that is not responding well to other types of treatment (this would usually require an emergency heart bypass procedure).

Tests and Labs

Tests done days or weeks before surgery to ensure a person is stable enough to have heart bypass surgery, or to establish criteria for getting bypass surgery include:

  • Complete blood count (CBC): Done before surgery to diagnose anemia, those with severe anemia will require treatment before surgery can be performed. In some instances, a blood transfusion is given during surgery to people with severe anemia.
  • Coagulation tests: These blood tests are performed to ensure that a person’s blood clots normally, aimed at avoiding any problems with excessive bleeding during or after surgery.
  • Miscellaneous blood tests: These are performed to check to see if the liver and kidneys are working properly before surgery.
  • Chest X-ray: A radiographic image is taken to evaluate factors such as the size and shape of the heart and aorta, as well as the appearance of the lungs.
  • Cardiac catheterization: An imaging procedure (when angiography, a procedure that involves injecting dye into the blood vessels so they can be viewed) that involves allowing the healthcare provider to view your coronary arteries to evaluate the location and severity of the blockages.
  • A resting electrocardiogram (ECG): This test measures the electrical activity of the heart, performed to help your surgeon evaluate how well your heart is functioning, may help diagnose CAD.
  • Stress electrocardiography: An imaging test that is performed while a person engages in physical exercise, designed to help detect ischemia (death of tissue from lack of oxygen) in the myocardium (heart muscle), may help to diagnose angina.

Other tests that help evaluate the severity of coronary artery disease and determine if bypass surgery is best for you include:

  • Nuclear imaging: A dose of radioactive tracer material is given orally (by mouth) and a scan detects this radiation from various parts of the body to produce images.
  • Ultrasound tests: This includes an echocardiogram, which uses high-frequency sound waves to create images of the heart and its pumping action.
  • Computed tomography (CT) scan: This involves taking a series of images at different angles inside the chest.
  • Magnetic resonance imaging (MRI): This scan uses radio waves and magnetic fields to create a series of detailed images of the internal structures of the chest.

A Word From Verywell

It’s important to understand that while a heart bypass procedure can improve your symptoms—such as pain from angina or shortness of breath—and lends itself to lowering the risk of future cardiovascular events (such as a heart attack or stroke), it is not considered a cure for coronary artery disease.

For some people, heart bypass surgery may even lower the risk of dying from heart disease. But, once you’ve had your heart bypass procedure, the real work of recovery has just begun.

Next, you must begin to implement major changes in diet and lifestyle. These changes often include eating a heart-healthy diet, exercising regularly, managing stress on a daily basis, and quitting smoking and/or drinking.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Sherry Christiansen
Sherry Christiansen is a medical writer with a healthcare background. She has worked in the hospital setting and collaborated on Alzheimer's research.