Coronary artery bypass grafting (CABG) is a surgical procedure used to improve blood flow to the heart when one or more coronary arteries are significantly narrowed or blocked. Instead of removing the blockage, the surgeon creates a new pathway for blood to reach the heart muscle beyond the diseased section.
The new pathway is made using a healthy blood vessel, or graft, taken from another part of the body. Depending on the patient's coronary anatomy, more than one graft may be needed. If you are looking for a broader overview of the procedure, you can also explore our guide to Coronary Artery Bypass Grafting (CABG).
What happens before CABG surgery?
CABG begins with careful preparation. Before surgery, the cardiac team reviews the patient's coronary angiogram and other investigations to understand where the arteries are narrowed and which areas of the heart require improved blood flow.
The assessment may include:
- Coronary angiography
- Electrocardiography (ECG)
- Echocardiography
- Blood tests
- Assessment of kidney and lung function
- Evaluation of overall surgical risk
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
Step 1: General anaesthesia
CABG is normally performed under general anaesthesia, meaning you are completely asleep during the operation. An anaesthesia team monitors your heart rhythm, blood pressure, oxygen levels and other vital functions throughout the surgery.
Several intravenous lines and monitoring devices may be placed before or after you are asleep. A breathing tube is inserted into the airway, and a ventilator supports breathing during the operation.
Step 2: Preparing the blood vessels for the grafts
Before the bypasses can be created, the surgeon needs suitable blood vessels to use as grafts. Common sources include:
- Internal mammary artery: an artery located inside the chest
- Radial artery: an artery from the forearm
- Saphenous vein: a vein from the leg
The choice depends on the patient's coronary anatomy, the number of bypasses needed, the condition of the potential graft vessels and other medical factors.
Step 3: Reaching the heart
In conventional CABG, the surgeon makes an incision along the centre of the chest and divides the breastbone, or sternum, to reach the heart. This is known as a median sternotomy.
Once the chest is opened, the surgeon can directly access the heart and coronary arteries. Not every patient requires the conventional approach. Selected patients may be suitable for minimally invasive CABG, in which smaller incisions are used. This depends on the location of the coronary blockage, the number of vessels requiring bypass and the patient's individual anatomy.
Step 4: Choosing how the heart will be supported during surgery
CABG can be performed using either an on-pump or off-pump technique.
On-pump CABG
In conventional on-pump surgery, a heart-lung machine, also called a cardiopulmonary bypass machine, temporarily takes over the functions of the heart and lungs.
The machine keeps oxygen-rich blood circulating throughout the body while the surgeon operates on the heart. The heart can be temporarily stopped so that the surgeon can create the bypass connections on a relatively still surface.
Once the grafts have been completed and the team is satisfied with the results, the heart is allowed to resume its normal activity and the patient is gradually disconnected from the heart-lung machine.
Off-pump CABG
In off-pump CABG, the heart continues beating during the operation. Special stabilising equipment is used to reduce movement in the small area where the surgeon is connecting the graft.
This approach avoids the use of the heart-lung machine. It may be considered in selected patients, particularly when avoiding manipulation of a heavily calcified aorta or reducing certain procedural risks is important.
Step 5: Creating the bypasses
This is the central part of CABG surgery. The surgeon connects the graft so that blood can travel around the blocked or severely narrowed section of the coronary artery.
For a vein or free arterial graft, one end is generally connected to a source of blood flow, such as the aorta, while the other end is connected to the coronary artery beyond the blockage.
With an internal mammary artery graft, the artery can remain connected to its natural blood supply at one end and is connected to the coronary artery at the other end. Once the connection is complete, blood has a new route to reach the heart muscle.
Step 6: Creating more than one bypass when needed
A patient may have significant disease in several coronary arteries. In that situation, the surgeon can create multiple grafts during the same operation. This is where terms such as double bypass, triple bypass and quadruple bypass come from.
These terms describe the number of coronary targets that are bypassed, not necessarily the number of different graft types used. For example, a patient undergoing triple bypass surgery could receive an internal mammary artery graft, a radial artery graft and a saphenous vein graft.
Step 7: Checking the bypasses
After the grafts have been connected, the surgical team checks that blood can flow properly through the new pathways.
The team also evaluates the heart's function and looks for any immediate surgical problems that need to be addressed before closing the chest. Once the surgeon is satisfied with the bypasses and the patient's condition is stable, the operation moves to the closure stage.
Step 8: Bringing the heart back to its normal function
For patients who undergo on-pump CABG, the heart-lung machine is gradually withdrawn once the heart is functioning adequately. The patient's heart resumes its normal pumping function, and the surgical team confirms that circulation and vital signs are stable.
For off-pump CABG, this step involving separation from the heart-lung machine is not required because the heart has continued beating throughout the operation.
Step 9: Closing the chest
After the bypasses are completed, the surgeon closes the breastbone using strong surgical wires. These wires normally remain in place permanently and provide support while the breastbone heals.
The skin incision is then closed with appropriate surgical techniques. Small drainage tubes may be left temporarily in the chest to remove blood or other fluid that can collect after surgery.
How long does CABG surgery take?
A conventional CABG operation commonly takes around 3 to 6 hours, although the actual duration can be shorter or longer depending on the complexity of the operation.
The number of bypasses, the patient's anatomy, the type of grafts required and whether additional procedures are performed can all affect the operating time. Therefore, the length of the operation should not be interpreted on its own as an indication of whether surgery has gone well.
What happens immediately after CABG?
After surgery, the patient is usually transferred to an intensive care unit (ICU) or specialised cardiac critical-care area. During the early recovery period, the medical team closely monitors:
- Heart rhythm
- Blood pressure
- Oxygen levels
- Heart and lung function
- Bleeding and chest drainage
- Kidney function
A breathing tube may remain in place initially while the patient recovers from anaesthesia. It is usually removed once the patient is awake enough and able to breathe adequately without ventilator support.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
When does the patient leave intensive care?
The timing varies according to the patient's condition and how smoothly recovery progresses. Once the patient's heart, lungs and other vital functions are stable, they are generally transferred from intensive care to a cardiac or surgical ward.
During this period, the focus gradually shifts from close monitoring to mobilisation, breathing exercises, pain control, wound care and preparation for discharge.
What happens during the first few days after surgery?
The first days after CABG are focused on helping the body recover from major surgery while preventing complications. The care team may encourage the patient to:
- Sit up and gradually begin walking
- Perform breathing exercises
- Cough carefully to clear the lungs
- Eat and drink as tolerated
- Take prescribed medicines
- Participate in early cardiac rehabilitation activities
How long does recovery take?
Hospital recovery after CABG varies, but many patients remain in hospital for approximately a week, depending on their condition and the type of surgery performed. Recovery continues after discharge.
The breastbone and other tissues need time to heal, and energy levels may take several weeks to improve. Full recovery can take several weeks to a few months, depending on age, overall health, the complexity of surgery and whether complications occurred.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
What happens to the original blocked artery?
CABG does not normally remove the plaque from the original coronary artery. Instead, the graft creates a new route for blood to travel around the diseased section.
This is why long-term treatment remains important after surgery. CABG improves blood flow but does not eliminate the underlying coronary artery disease that caused the blockage.
Can CABG be performed without opening the breastbone?
In selected patients, yes. Minimally invasive and off-pump approaches can be used in certain circumstances, depending on the number and location of coronary arteries that require bypassing and the patient's anatomy.
However, these approaches are not appropriate for everyone. Conventional CABG through a median sternotomy remains the standard approach for many patients, particularly when several coronary arteries require bypassing.
The Bottom Line
CABG is performed by creating new pathways for blood to reach the heart muscle beyond blocked or severely narrowed coronary arteries. The operation involves harvesting suitable blood vessels, accessing the heart, connecting the grafts to the coronary arteries and carefully checking the new blood-flow pathways.
Most conventional procedures involve opening the breastbone and temporarily using a heart-lung machine, although off-pump and minimally invasive approaches may be appropriate for selected patients.
After the bypasses are completed, the chest is closed and the patient is moved to intensive cardiac monitoring before beginning the recovery process.
Although the operation itself may take several hours, CABG is more than the time spent in the operating room. Careful planning before surgery, close monitoring afterward and gradual rehabilitation are all important parts of successful recovery.
