Coronary artery bypass grafting (CABG) is a major heart operation that can improve blood flow to the heart and, for appropriately selected patients, reduce symptoms and important cardiovascular risks. Like any major surgery, however, CABG carries potential risks and complications.
Some complications are relatively common and temporary, while others are less common but can be serious. The level of risk is not the same for everyone.
It depends on factors such as age, overall health, heart function, kidney and lung health, diabetes, the urgency and complexity of surgery, and whether other procedures are being performed at the same time. If you want to understand the procedure itself, you can also read our guide to Coronary Artery Bypass Grafting (CABG).
Is CABG surgery risky?
Yes. CABG is a major surgical procedure, so complications are possible. However, the presence of surgical risk does not mean that CABG is unsafe or inappropriate.
CABG is recommended when the expected benefits of restoring blood flow outweigh the risks of the operation for that particular patient. Before surgery, the cardiac team evaluates the patient's individual risk rather than relying only on average figures.
For some people, particularly those with complex coronary artery disease, the risk of leaving the underlying heart disease untreated may be greater than the risk associated with surgery.
What are the main risks of CABG?
The possible complications can affect different parts of the body because CABG involves the heart, blood vessels, chest and other organ systems. The main risks include:
- Bleeding
- Heart rhythm disturbances
- Wound or other infections
- Kidney problems
- Breathing or lung complications
- Heart attack
- Stroke
- Blood clots
- Temporary memory or concentration problems
- Problems involving the bypass grafts
- Rarely, severe complications that can be life-threatening
1. Bleeding after CABG
Bleeding is one of the complications doctors monitor closely after bypass surgery. Because CABG involves major blood vessels and surgery around the heart, some bleeding is expected after the operation. Chest drainage tubes are commonly used to remove blood and fluid that collect after surgery.
In some patients, bleeding can become excessive. This may require a blood transfusion and, occasionally, another procedure or surgery to identify and control the source. The surgical and intensive-care teams monitor drainage and blood counts closely during the early recovery period.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
2. Irregular heart rhythm
Changes in heart rhythm, particularly atrial fibrillation, are common after CABG. Atrial fibrillation causes the heart to beat irregularly and sometimes rapidly. It often develops during the first few days after heart surgery.
In many patients, this rhythm problem is temporary and settles as recovery progresses. Medicines may be used to control the heart rate or rhythm, and additional treatment may be considered when necessary.
Although postoperative atrial fibrillation is often temporary, it is important because abnormal rhythms can affect recovery and, in some circumstances, increase the risk of complications such as stroke.
3. Infection
Infection can develop at the chest incision or at another site where a blood vessel was removed for use as a graft. Signs that may suggest a wound infection include increasing redness, swelling, pain, warmth, discharge or fever.
Most wound infections can be treated, particularly when recognised early. More serious infections require more intensive treatment. Good wound care and following postoperative instructions are important parts of reducing infection risk.
4. Kidney problems
The kidneys can be affected by major surgery, changes in blood flow and other factors during and after CABG. Some patients experience a temporary decline in kidney function that improves during recovery.
In more serious cases, kidney injury can become severe enough to require dialysis. The risk is higher in people who already have kidney disease before surgery. This is one reason kidney function is assessed before CABG and monitored closely afterward.
5. Breathing and lung complications
Because CABG involves major chest surgery and general anaesthesia, temporary breathing problems can occur. Patients may have difficulty taking deep breaths, clearing mucus from the lungs or maintaining normal lung function immediately after surgery.
Breathing exercises, early mobilisation and physiotherapy are commonly used to support recovery. People with pre-existing lung disease or other factors affecting breathing may have a higher risk of postoperative respiratory complications.
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
6. Heart attack
A heart attack can rarely occur during or shortly after CABG. Heart muscle can be affected by changes in blood flow or other complications related to the operation. Postoperative heart problems require immediate assessment and treatment.
The risk is influenced by factors such as the patient's underlying coronary disease, heart function and whether the operation is planned or performed urgently.
Because some changes in heart-related blood tests can occur after major surgery, doctors use the overall clinical picture and appropriate investigations when assessing possible postoperative heart injury.
7. Stroke
Stroke is an uncommon but potentially serious complication of CABG. A stroke can occur when blood flow to part of the brain is interrupted, including when a blood clot or other material travels to the brain.
Risk is influenced by factors such as age, previous stroke or transient ischemic attack, blood-vessel disease, high blood pressure, diabetes, kidney disease and other cardiovascular conditions.
Stroke risk is one of the reasons the surgical team carefully evaluates a patient's medical history and vascular risk before surgery.
8. Temporary memory and concentration problems
Some patients notice changes in memory, concentration or mental clarity after CABG. These changes may be particularly noticeable during the early recovery period and can be related to the stress of major surgery, anaesthesia, sleep disruption, medications and other factors.
For many people, these problems improve gradually over the following weeks or months. However, significant or persistent cognitive changes should be discussed with the medical team rather than assumed to be a normal part of recovery.
9. Blood clots
Major surgery and periods of reduced mobility can increase the risk of blood clots. Blood clots can develop in the veins of the legs and, in serious cases, travel to the lungs. Hospitals use measures such as early mobilisation, appropriate medicines and other preventive strategies according to the patient's individual risk.
10. Problems with the bypass graft
The bypass itself can develop problems over time. A graft can become narrowed or blocked, particularly as coronary artery disease continues to progress. The likelihood varies according to the type of graft and other patient-specific factors.
This is an important point to understand: CABG improves blood flow, but it does not cure the underlying process that causes coronary artery disease.
Long-term prevention therefore remains important after surgery. Current guidance emphasises measures such as appropriate antiplatelet therapy, cholesterol reduction, risk-factor management and cardiac rehabilitation to help protect grafts and reduce future cardiovascular events.
11. Chest and wound-related problems
The breastbone and chest tissues need time to heal after conventional CABG. Patients may experience pain, tightness, numbness or sensitivity around the incision during recovery. These symptoms often improve gradually.
More significant problems, such as wound infection or abnormal healing of the breastbone, require medical assessment. Following instructions about lifting, movement and wound care helps protect the healing chest.
12. Complications related to the areas used for graft harvesting
CABG may involve taking a blood vessel from the chest, arm or leg. The area used to obtain the graft therefore has its own recovery process.
Possible problems can include pain, swelling, numbness, bruising, infection or delayed wound healing at the harvesting site. These issues are usually managed as part of the overall postoperative recovery, although more significant complications may require additional treatment.
13. Fluid retention and swelling
Swelling, particularly in the legs, can occur after CABG. It may be related to changes in fluid balance, reduced mobility or the site from which a vein was harvested.
It often improves as mobility increases and the body restores its normal fluid balance. However, new or rapidly increasing swelling, especially when accompanied by pain or breathing difficulty, should be assessed promptly.
Which patients have a higher risk of CABG complications?
*AI-generated image - for illustration only. Clinical accuracy is not guaranteed.
The risk of complications is not determined by age alone. Several factors can influence how safely a person can undergo CABG and how quickly they recover. Risk may be higher in patients with:
- Advanced age or frailty
- Reduced heart-pumping function
- Diabetes
- Chronic kidney disease
- Significant lung disease
- Previous stroke or other vascular disease
- Severe or extensive coronary artery disease
- Smoking history
- Other serious medical conditions
- A need for emergency rather than planned surgery
- Additional cardiac procedures performed during the same operation
Is emergency CABG riskier than planned CABG?
Emergency surgery can carry a different risk profile from a planned operation. A patient requiring urgent CABG may already have experienced a heart attack, unstable coronary disease or another serious cardiovascular problem. There may also be less time to optimise other medical conditions before surgery.
As a result, the overall risk can be higher in emergency situations than in carefully planned surgery. However, emergency CABG may still be the safest or necessary treatment when the underlying heart condition itself poses an immediate threat.
Can CABG complications be prevented?
Not every complication can be prevented, but careful preparation and postoperative management can reduce risk and help identify problems early. Before surgery, the medical team may assess:
- Heart function
- Kidney function
- Lung function
- Blood sugar control
- Blood pressure
- Blood cholesterol
- Smoking status
- Previous stroke or vascular disease
- Current medicines
After surgery, early mobilisation, breathing exercises, appropriate medicines, wound care and cardiac rehabilitation all form part of safe recovery. Long-term prevention is equally important because coronary artery disease can continue to progress even after successful bypass surgery.
What symptoms should you watch for after CABG?
Some discomfort and tiredness are expected during recovery, but certain changes should not be ignored. Contact your medical team if you develop symptoms such as:
- Increasing redness, swelling, pain or discharge from a surgical wound
- Fever or chills
- New or worsening heart palpitations
- Increasing shortness of breath
- Unusual or worsening swelling
- Bleeding from a surgical wound
- A significant deterioration in your general condition
Sudden severe chest pain, severe breathing difficulty, or signs of stroke such as facial drooping, difficulty speaking or sudden weakness require emergency medical attention.
Do the benefits of CABG outweigh the risks?
This is ultimately an individual medical decision. CABG is generally recommended only when the cardiac team believes that revascularisation offers meaningful benefit compared with the risks of surgery and the risks of leaving the coronary disease untreated.
For patients with appropriate patterns of coronary disease, CABG can improve blood flow, relieve angina and provide important long-term benefits. The potential benefit has to be considered alongside the patient's individual operative risk.
This is why the decision should not be based on the question, “Is CABG risky?” alone. The more useful question is: “What are the expected benefits and risks of CABG for this particular patient?”
The Bottom Line
CABG is a major operation, so it carries real risks, but serious complications are not inevitable. Many patients recover without major problems, while the cardiac team monitors closely for complications that can occur during or after surgery.
Some postoperative problems, such as irregular heart rhythm, fatigue, pain and temporary changes in kidney function or memory, may improve as recovery progresses. Other complications, including major bleeding, heart attack, stroke, severe infection or serious organ problems, can be more significant and require urgent treatment.
Your personal risk depends on much more than the fact that you are having bypass surgery. Age, heart function, kidney and lung health, diabetes, vascular disease, the complexity of coronary disease and whether surgery is planned or urgent can all influence the outcome.
Finally, the risk assessment should always be viewed alongside the reason CABG has been recommended. In patients for whom bypass surgery is appropriate, the expected benefit of improving blood flow and reducing the consequences of severe coronary disease may outweigh the operative risks. Careful preoperative assessment, experienced surgical care, appropriate postoperative monitoring and long-term secondary prevention all play important roles in achieving the best possible outcome.
