Coronary Artery Bypass Grafting

Coronary artery bypass grafting is surgical revascularisation using conduits that bypass obstructive coronary lesions. It remains the most common cardiac operation in adults, and gives durable survival benefit in selected patients with complex or multivessel disease.

Indications

• Left main stenosis of 50% or more, especially with high SYNTAX score.
• Three vessel disease, particularly in diabetes or with ejection fraction of 35% or less.
• Two vessel disease with proximal LAD involvement.
• Multivessel disease with diabetes: survival is better with surgery than with PCI.
• Failed or unsuitable PCI, ongoing ischaemia with complex anatomy, and mechanical complications of infarction requiring surgery.
• Concomitant procedure at the time of valve or aortic surgery in significant coronary disease.

Conduits and patency

• Left internal mammary artery to the LAD: the gold standard, with 90 to 95% patency at 10 years and a clear survival benefit.
• Right internal mammary artery and radial artery: arterial grafts with better long-term patency than vein (radial about 85 to 90% at 5 to 10 years), used for targets with more than 70% stenosis. Radial artery is avoided when the Allen test or Doppler indicates poor ulnar collateral flow, and after transradial catheterisation. Total arterial revascularisation is considered in younger patients.
• Great saphenous vein: the commonest conduit. Failure occurs in 10 to 15% in the first year, about 20 to 30% by 5 years and up to 50% by 10 years from intimal hyperplasia and later atherosclerosis. No-touch harvesting and endoscopic harvesting improve patency and reduce wound complications.

Techniques

• On-pump surgery: median sternotomy, cardiopulmonary bypass and cardioplegic arrest, giving a still field.
• Off-pump (OPCAB): beating heart with stabilisers. It reduces stroke and transfusion in some series, but may have lower graft patency and incomplete revascularisation, so it depends on surgeon experience. It is useful with severe aortic atheroma.
• Minimally invasive: minimally invasive direct coronary bypass (left anterior thoracotomy) for isolated LAD disease, robotic-assisted procedures, and hybrid revascularisation (LIMA to LAD plus PCI to other vessels).

Outcomes

• Operative mortality for isolated first-time bypass is 1 to 3%. It is higher in emergency surgery, reduced ejection fraction, renal failure and advanced age.
• Risk is quantified with the EuroSCORE II or the Society of Thoracic Surgeons score.
• Predictors of poor outcome: age over 75 years, diabetes, chronic kidney disease, chronic obstructive pulmonary disease, previous cardiac surgery, peripheral arterial disease, and recent infarction.

Patients are assessed for appropriateness through symptoms, anatomy and comorbidity.

Preoperative considerations

• Angina class, heart failure symptoms, prior stroke, carotid bruits and peripheral pulses.
• Frailty, cognitive function, nutritional status, and dental health.
• Smoking, diabetes, renal function, and chronic lung disease.

Clinical features after surgery

• Sternal wound: pain, erythema, discharge or instability. Deep sternal infection occurs in 1 to 3%, with higher risk in diabetes, obesity, bilateral internal mammary artery use, and prolonged operation.
• Postoperative atrial fibrillation: 20 to 40%, peaking on days 2 to 3.
• Pericardial effusion and tamponade: low cardiac output, hypotension, raised venous pressure, and falling chest drain output despite instability.
• Neurological: stroke in 1 to 2%, and delirium in up to 30%, with postoperative cognitive decline.
• Renal: acute kidney injury in 15 to 30%, dialysis in 1 to 3%.
• Respiratory: atelectasis, pleural effusion, phrenic nerve injury and pneumonia.
• Vasoplegia: low systemic vascular resistance and high cardiac output, with hypotension.
• Bleeding: requiring re-exploration in 2 to 4%.
• Postpericardiotomy syndrome: fever, pleuritic pain and pericardial rub weeks after surgery.
• Graft failure: recurrent angina, ECG changes or new regional wall motion abnormality.
• Harvest-site problems: leg wound infection and neuralgia, saphenous nerve injury, and radial harvest numbness.

Red flags: persistent hypotension with rising filling pressures, drain output over 200 mL/hour for 2 to 4 hours, new ST elevation, fever with sternal click, and new focal neurological deficit.

Preoperative evaluation

• Coronary angiography, with left ventricular function assessment by echocardiography, and viability assessment (cardiac MRI or dobutamine echo) when ejection fraction is low.
• Carotid duplex in patients over 70, with a history of stroke or TIA, left main disease or peripheral arterial disease.
• Laboratory tests: CBC, creatinine and eGFR, coagulation screen, HbA1c, liver tests, albumin, group and cross-match, and screening swabs for MRSA.
• Pulmonary function tests in chronic lung disease, and pregnancy test where applicable.
• Vein mapping or Allen test and radial artery Doppler when arterial conduits are planned.
• Chest CT or epiaortic ultrasound for ascending aortic atheroma when off-pump or no-touch aortic techniques are considered.

Postoperative evaluation

• ECG, chest radiograph, arterial blood gases, lactate, troponin (a rise above 10 times the upper limit within 48 hours, with new Q waves, angiographic graft occlusion, or new regional wall motion abnormality, defines perioperative infarction), creatinine, haemoglobin and electrolytes.
• Echocardiography for hypotension, new murmurs, effusion or tamponade.
• Urgent angiography for suspected graft failure with ischaemia, ventricular arrhythmia, or new ventricular dysfunction.
• Blood cultures, sternal CT and wound cultures for suspected sternal infection.

Preoperative

• Continue aspirin 75 to 100 mg daily, beta blockers, statins and ACE inhibitors may be withheld on the morning of surgery per local practice.
• Stop clopidogrel 5 days, ticagrelor 3 to 5 days and prasugrel 7 days before elective surgery. Urgent surgery proceeds with higher bleeding risk.
• Stop SGLT2 inhibitors 3 to 4 days beforehand. Hold metformin and DOACs (24 to 48 hours, longer in renal impairment). Warfarin is stopped 5 days beforehand.
• Optimise glucose (HbA1c under 8% ideally), treat anaemia, stop smoking for at least 4 weeks, and decolonise MRSA (mupirocin 2% nasal ointment twice daily for 5 days with chlorhexidine washes).
• Prophylactic antibiotics: cefazolin 2 g IV (3 g if over 120 kg) within 60 minutes before incision, repeated every 4 hours or at 1500 mL blood loss. Cefuroxime 1.5 g is an alternative. Add vancomycin 15 mg/kg for MRSA risk. Continue for 24 to 48 hours at most.

Intraoperative

• Heparin 300 to 400 units/kg to ACT of 480 seconds or more for cardiopulmonary bypass, reversed with protamine at about 1 mg per 100 units of heparin.
• Tranexamic acid 10 to 30 mg/kg bolus then 1 to 16 mg/kg/h reduces bleeding. Higher doses may cause seizures.
• Cardioplegia, temperature management, and glucose control with insulin infusion to 140 to 180 mg/dL.

Early postoperative care

• ICU monitoring, lung-protective ventilation, early extubation within 6 hours, and analgesia with paracetamol 1 g every 6 hours, NSAID avoidance, low-dose opioids and regional blocks.
• Aspirin 75 to 100 mg within 6 hours of surgery and continued lifelong. This improves vein graft patency.
• Dual antiplatelet therapy (aspirin plus clopidogrel 75 mg or ticagrelor 90 mg twice daily) for 12 months after bypass for acute coronary syndrome, and it can be considered for off-pump surgery and elective cases.
• Resume beta blockers early (metoprolol 25 to 50 mg twice daily), and statins immediately.
• Transfusion threshold haemoglobin 7.5 g/dL. Maintain mean arterial pressure at 65 to 80 mmHg.
• Chest drains removed when output is below 100 mL over 8 hours.
• Thromboprophylaxis with enoxaparin 40 mg daily from day 1 to 2, plus compression devices. Stress ulcer prophylaxis with a proton pump inhibitor.

Complications

• Postoperative atrial fibrillation: beta blockers reduce incidence. Prophylactic amiodarone (loading 5 to 10 mg/kg/day orally pre-operatively, or 150 mg IV bolus then infusion) is used in high-risk patients. Correct potassium to 4.5 mmol/L or above and magnesium to 2 mmol/L or above. Rate control with metoprolol or diltiazem. Amiodarone 150 mg IV over 10 minutes, then 1 mg/min for 6 hours, then 0.5 mg/min for 18 hours. Synchronised cardioversion if unstable. Start anticoagulation if AF lasts more than 48 hours (apixaban 5 mg twice daily for at least 4 weeks and often 3 months).
• Tamponade: emergency re-sternotomy.
• Vasoplegia: norepinephrine 0.05 to 0.5 micrograms/kg/min, vasopressin 0.01 to 0.04 units/min, and methylene blue 1.5 to 2 mg/kg IV over 20 to 60 minutes in refractory cases.
• Low cardiac output: inotropes (dobutamine 2 to 10 micrograms/kg/min, milrinone 0.25 to 0.5 micrograms/kg/min), intra-aortic balloon pump or mechanical support.
• Bleeding: correction of coagulopathy with protamine, platelets, fresh frozen plasma or fibrinogen concentrate, prothrombin complex concentrate, and re-exploration if surgical.
• Acute kidney injury: avoid nephrotoxins, optimise perfusion, and start renal replacement for standard indications.
• Sternal wound infection: debridement, vacuum-assisted closure, culture-directed antibiotics (vancomycin 15 to 20 mg/kg every 8 to 12 hours until cultures return) for 4 to 6 weeks for mediastinitis, with flap reconstruction.
• Postpericardiotomy syndrome: colchicine 0.5 mg twice daily (once daily if under 70 kg) for 1 to 3 months with ibuprofen 600 mg every 8 hours for 2 weeks and a proton pump inhibitor.
• Perioperative infarction or graft failure: urgent angiography, PCI of the native vessel or graft, or re-do surgery.
• Stroke: emergency imaging and neurology review. Thrombolysis is contraindicated within 14 days of major surgery.
• Delirium: non-pharmacological measures, avoid benzodiazepines, and use low-dose haloperidol 0.5 to 1 mg only for distressing agitation.

Rehabilitation and long-term care

• Sternal precautions for 6 to 8 weeks (no lifting over 4.5 kg, no pushing or pulling), splinting the chest during cough, and avoiding driving for 4 to 6 weeks.
• Cardiac rehabilitation beginning within 2 to 4 weeks, which lowers mortality and readmission.
• Long-term medical therapy as in chronic coronary disease: aspirin, high-intensity statin with LDL target under 55 mg/dL, ACE inhibitor, beta blocker for infarction or reduced ejection fraction, and risk factor control.
• Follow-up at 6 weeks and 3 months, and then annually, with stress testing or CT angiography for recurrent symptoms.
• Recurrent angina: medical therapy first, with PCI of failing grafts or native vessels, or re-do surgery.