The heart is a muscle with four chambers. Its right side pumps blood to the lungs, where it takes up oxygen. Its left side pumps oxygen-rich blood through the aorta to the body. Valves help blood move in the right direction. Each heartbeat supports that circuit, but the heart muscle itself also needs a continuous supply of oxygen and nutrients.

The coronary arteries branch from the aorta and run over the surface of the heart, supplying the muscle beneath. Fatty material can build up in their walls, a process called atherosclerosis, narrowing the channel for blood. A narrowing can leave the heart short of blood during exertion and cause angina. A clot forming at a damaged plaque can abruptly block an artery and cause a heart attack.

A bypass creates another route for blood to reach heart muscle beyond a narrowing. It does not replace the heart or clean out all the original artery disease. The number and location of affected arteries, the quality of the vessels and how well the heart pumps all help the team decide what treatment might help.

CABG may be discussed when coronary disease causes symptoms such as angina or breathlessness despite treatment, when angioplasty is unsuitable, or when the pattern of disease carries a high risk of heart attack. For some people, surgery is considered to improve outlook as well as symptoms. The intended benefit should be explained in relation to your own disease, rather than assumed to be the same for everyone.

In a planned assessment, a coronary angiogram shows where the arteries are narrowed and helps guide the choice of treatment. Depending on the situation, other tests can assess heart function or how much the blood supply is affected. Ask the team to show you the relevant vessels and explain why each proposed treatment is or is not suitable.

A bypass can also be urgent or an emergency, including after severe symptoms or a heart attack. Treatment depends on the immediate problem. For an eligible person with an acute STEMI heart attack, NICE recommends rapid coronary angiography with primary angioplasty if indicated when it can be delivered within the guideline time window. There may be less time for a long elective discussion, but the team should explain the plan as circumstances allow.

For stable angina, NICE recommends medicines initially: anti-anginal drugs reduce episodes, while other medicines help lower the risk of future cardiovascular events. A beta blocker or calcium channel blocker may be offered for symptoms; the regimen depends on other conditions, side effects and preferences. GTN may be prescribed for attacks. Medication and risk-factor management remain important even when a procedure is performed.

Angioplasty, also called PCI, uses a catheter usually inserted through the wrist or groin. A balloon opens a narrowed section and a small mesh stent is often left in place. CABG is major surgery that routes blood around the narrowing using a graft. PCI generally involves a shorter recovery, but may not be suitable for every pattern of disease; either procedure can later need further treatment.

NICE recommends considering revascularisation, meaning PCI or CABG, when stable-angina symptoms are not adequately controlled with optimal medicines. A multidisciplinary team can weigh the number and complexity of narrowings, other health conditions and individual preferences. CABG may offer a survival advantage for some people with multivessel disease, including certain people with diabetes or complex three-vessel disease. Even if symptoms are controlled, some patterns such as left main or proximal three-vessel disease can warrant discussing surgery for prognosis.

Evidence in context: the FREEDOM trial randomly assigned 1,900 adults with diabetes and multivessel disease to CABG or PCI with drug-eluting stents. At five years the combined outcome of death, nonfatal heart attack or nonfatal stroke was lower after CABG, while stroke was more frequent after CABG. The study excluded left-main narrowing and mainly used older stent types. Its group results do not predict your individual benefit or risk; ask how current evidence applies to you.

A graft is a healthy blood vessel used to make a detour. The surgeon may use an artery from the chest or arm, or a vein from the leg. An artery from the chest can remain attached to its original blood supply, with its other end connected beyond a coronary narrowing. The team chooses vessels for your anatomy and operation.

A double or triple bypass describes how many bypasses are made, not a replacement of two or three hearts or a measure of how well the operation will work. You may have wounds where vessels were taken as well as on the chest. Grafts can narrow or fail over time and disease may progress in other vessels, so follow-up and treatment of coronary disease still matter.

Pre-operative assessment covers your health, previous tests, medicines and home circumstances; further blood tests or other checks may be needed. Give the team a full list of prescriptions, over-the-counter products, vitamins and herbal supplements, and tell them about allergies and other conditions. Follow your hospital’s individual instructions on medicines and fasting. Do not stop antiplatelets, anticoagulants or other prescribed medicines on your own.

Arrange transport home and help for the first days after discharge, and discuss time off work and any caring responsibilities. If you develop a cough, cold or fever before surgery, tell the surgical team. Ask what will happen if the operation is postponed, what symptoms mean you should seek help while waiting, and who to call.

CABG is performed under general anaesthetic, so you are asleep. Most often the surgeon opens the chest through the breastbone to reach the heart and prepares the graft vessels. Usually a heart-lung machine keeps blood circulating while the heart is operated on. Some bypasses are done on a beating heart without that machine; selected people may be offered a less invasive approach through smaller cuts.

The surgeon connects the grafts to carry blood beyond the narrowed sections. Once grafting is complete, the team restores the heart’s pumping and disconnects the heart-lung machine if used. When the breastbone has been divided, it is usually secured with metal wires that remain in place, and the skin is closed. The operation usually takes three to six hours, though your circumstances may differ.

Afterwards you usually go to intensive care or a specialist recovery area. Equipment monitors your heart and lungs; a breathing tube and ventilator may be needed initially, and chest drains remove fluid. These are removed as you recover. Staff provide pain relief and help you begin moving safely.

The aim is to improve blood flow to heart muscle. In stable angina, bypass may relieve symptoms and improve daily activity; in selected patterns of disease it may also improve survival. Improvement is not guaranteed, and the size of the benefit depends on your diagnosis, symptoms and other health conditions. Ask what benefit matters most in your case and what might happen without surgery.

Complications include wound infection, bleeding that may require transfusion or another operation, irregular heart rhythm, kidney problems, heart attack and stroke. Some people experience memory problems that usually improve over months. Serious complications can be life-threatening. Risks vary with the urgency of surgery, existing health and the planned procedure; your team can explain your personal risk and how they plan to reduce it.

Most people spend about a week in hospital, usually moving from intensive care to a ward after one or two days. Nurses and physiotherapists help you start getting out of bed and moving, often from the day after surgery. Before discharge, make sure you understand wound care, pain relief, prescribed medicines, follow-up and whom to contact if symptoms change.

Chest, back or shoulder discomfort and tiredness in the first weeks are common, and appetite may be reduced at first. Follow your team’s wound-care instructions and gradually resume activity as advised. NHS England says most usual activities can often resume after about six weeks and full recovery usually takes two to three months. These are guides, not a deadline: complications and other health conditions can change the timetable.

NHS England advises no heavy lifting for three months. Ask about a plan for walking, stairs, work, sex and lifting in your own situation. Cardiac rehabilitation combines exercise and education and can support physical and emotional recovery. Ask how to access it, including home or remote options. Anxiety, low mood or worries about returning to normal life deserve support too.

For Great Britain, GOV.UK says car and motorcycle drivers should stop driving for at least one month after bypass and restart only when a doctor says it is safe. Bus, coach and lorry drivers must notify DVLA and stop for at least three months, returning only when medically cleared. Rules and licensing arrangements can differ in Northern Ireland; check with your clinical team and the relevant licensing authority, and ask your insurer before driving again.

A graft treats the blood-flow problem but does not cure coronary heart disease. Continue medicines as prescribed and discuss any side effects rather than stopping them yourself. Treatment can include antiplatelet medicine and a statin; other drugs depend on your heart and other conditions. Your discharge list should explain any changes from your previous medicines.

Stopping smoking, a balanced diet, gradual activity and management of blood pressure, cholesterol and diabetes where relevant can help protect heart health. Cardiac rehabilitation and your GP can support a plan that fits your life. New or returning symptoms should be assessed: a past bypass does not make chest pain safe to ignore. Use the urgent guidance at the start of this guide.