Coronary Artery Bypass Graft (CABG) — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Coronary artery bypass graft surgery (CABG, commonly called 'bypass surgery') is a major cardiac surgical procedure that creates new pathways — bypass conduits — around blocked or severely narrowed coronary arteries, restoring oxygenated blood supply to ischaemic myocardium. The diseased coronary segments are not removed; instead, a graft vessel is connected upstream of the blockage and downstream to a patent coronary segment, physically bridging the obstruction. The left internal mammary artery (LIMA), harvested from the inner chest wall while preserving its proximal blood supply, is the preferred graft and is virtually always anastomosed to the left anterior descending artery (LAD) — the most critical coronary vessel supplying the anterior heart. Additional bypass targets use the right internal mammary artery (RIMA), radial artery (taken from the forearm under tourniquet), or reversed segments of the long saphenous vein from the leg. The number of bypasses reflects the extent of coronary disease: single, double, triple, or quadruple bypass. Most CABG procedures are performed on cardiopulmonary bypass (heart-lung machine) with cardioplegic cardiac arrest, though off-pump CABG (beating heart surgery) is used at specialist centres. CABG is the most extensively studied cardiac operation, with outcome data spanning more than five decades across hundreds of thousands of patients worldwide.

CABG is preferred over percutaneous coronary intervention (PCI, stenting) for complex coronary anatomy where complete revascularisation by stenting is not feasible or does not achieve equivalent long-term outcomes. The 2021 ACC/AHA joint guidelines and ESC guidelines specify the following as Class I (strong) indications for CABG: left main coronary artery disease with stenosis above 50%; three-vessel coronary disease (left anterior descending, circumflex, and right coronary arteries) with reduced left ventricular ejection fraction (below 35–40%); diabetes mellitus with multivessel coronary disease; and complex coronary anatomy unsuitable for PCI as assessed by the SYNTAX score. CABG is the standard of care for acute myocardial infarction complicated by mechanical complications — ventricular septal defect, papillary muscle rupture — and for patients in cardiogenic shock who fail medical treatment. In stable multivessel disease, the SYNTAX Trial demonstrated CABG superiority over PCI for major adverse cardiac events at 5 years in the intermediate and high SYNTAX score groups, particularly for diabetic patients. Emergency CABG after failed angioplasty or during acute MI is lifesaving but carries higher operative risk.

After intubation and general anaesthesia, the surgeon exposes the heart via median sternotomy — a vertical incision through the sternum. The LIMA is harvested as a pedicled graft from the inner surface of the chest wall using electrocautery and clips. Conduit veins or additional arterial grafts are harvested concurrently by a second surgeon. Cardiopulmonary bypass (CPB) is established by cannulating the ascending aorta and right atrium; the patient's blood is diverted through the heart-lung machine which oxygenates it and maintains circulation. The heart is arrested with cold cardioplegic solution (potassium-rich, which stops electrical and mechanical activity) and kept cold with topical ice slush to minimise ischaemic injury. With the still, bloodless operative field, the surgeon anastomoses the distal ends of each graft to the target coronary arteries beyond the obstruction using fine (7-0 or 8-0) polypropylene sutures under surgical loupes or a microscope. Proximal anastomoses (aorta-to-graft for venous grafts) are fashioned with the aortic cross-clamp partially released. The heart is defibrillated and normal rhythm restored. CPB is weaned as cardiac function returns, cannulae are removed, protamine reverses heparin anticoagulation, and the sternum is closed with stainless steel wires. Total operative time is 3–6 hours depending on the number of grafts and complexity.

CABG provides complete revascularisation of all significant coronary disease in a single procedure, a durable advantage over PCI for multivessel disease. The LIMA-to-LAD graft has an exceptional patency rate: 95% at 10 years and 80–85% at 20 years, far superior to the 50–60% 10-year patency of saphenous vein grafts. This durable patency translates into sustained freedom from recurrent angina, reduced myocardial infarction rates, and, critically, reduced mortality in high-risk patient groups. The STICH trial demonstrated that CABG reduces all-cause mortality by 16% compared with optimal medical therapy alone in patients with ischaemic cardiomyopathy (ejection fraction below 35%). In diabetic patients with multivessel disease, the FREEDOM trial showed CABG reduces 5-year death, myocardial infarction, and stroke by 27% compared with PCI with drug-eluting stents. Freedom from repeat revascularisation is 80–85% at 10 years after CABG versus 60–65% after PCI for complex multivessel disease. Angina is eliminated in more than 90% of patients immediately after surgery, with significant improvements in exercise capacity, quality of life, and ability to engage in normal activities within 6–12 weeks.

Operative mortality for elective CABG at high-volume specialist centres is 1–2% for isolated CABG without additional valve procedures or re-do surgery, rising to 3–5% in emergency CABG and 5–10% for re-do CABG (due to adhesions and scar tissue obscuring anatomy). Stroke occurs in 1–2% of elective cases, primarily from aortic manipulation releasing atheromatous debris; risk increases in older patients, those with heavily calcified aortas, and peripheral vascular disease. Post-operative atrial fibrillation complicates 20–30% of CABG procedures, peaking on post-operative days 2–3, managed with rate control and anticoagulation. Wound complications include sternal wound infection in 1–2% (higher in diabetics and bilateral IMA harvest) and leg wound complications from vein harvest in 3–10%. Post-operative cognitive dysfunction — subtle memory and concentration difficulties — occurs in 20–30% at 1 month and largely resolves by 6 months. Renal impairment requiring temporary or permanent dialysis affects less than 2% of elective cases. Graft failure (thrombosis) is prevented by aspirin therapy commenced within 6 hours of surgery.

The patient is transferred to the cardiac surgical ICU intubated and sedated, typically extubated within 4–8 hours. Chest drains are removed on day 1–2, and the patient is mobilised to a chair on day 1 and walking on day 2–3. ICU transfer to a cardiac surgery ward occurs on day 1–2. Hospital discharge is typically on day 5–7. Sternal healing takes 6–8 weeks: patients must avoid lifting more than 5 kg and driving during this period. The sternum is fully healed and load-bearing at 3 months. Prescribed medications include aspirin 75–100 mg daily indefinitely (or dual antiplatelet therapy in the first year if PCI was also performed), a high-intensity statin (atorvastatin 40–80 mg), beta-blocker, ACE inhibitor, and glycaemic management in diabetics. Cardiac rehabilitation — a supervised 8–12 week exercise and education programme — is strongly recommended and has been shown to reduce 1-year mortality by 20% and re-hospitalisation by 28%. Return to desk work is at 6–8 weeks, driving at 6 weeks, and manual work at 12 weeks. Sexual activity resumes at 6–8 weeks. Follow-up echocardiography is performed at 3–6 months to assess left ventricular recovery.