Abstract
Coronary Artery Bypass Grafting (CABG) is a surgical procedure to treat coronary artery disease by rerouting blood flow around blocked arteries using a healthy vessel from the leg or chest, restoring oxygen supply to the heart and relieving chest pain.
Introduction
Coronary artery disease (CAD) results from atherosclerotic plaque buildup that narrows coronary arteries, reducing blood flow and increasing the risk of myocardial infarction (heart attack). It can affect major vessels such as the left main stem, left anterior descending, circumflex, or right coronary arteries. Symptoms range from no discomfort to angina during exertion or at rest, and may progress to myocardial infarction, arrhythmia, or sudden death if blood flow is not restored. Diagnosis involves clinical assessment and noninvasive tests like ECG, chest X-ray, and echocardiography, while coronary angiography and CT angiography provide detailed visualization of arterial lesions. A >50% diameter loss indicates moderate stenosis, while >66% denotes severe narrowing. Advanced tools such as intravascular ultrasound and fractional flow reserve (FFR < 0.80) further assess plaque composition and stenosis severity.1
Indications and Procedure for Coronary Artery Bypass Surgery
Coronary Artery Bypass Grafting (CABG) restores blood flow to the heart when one or more coronary arteries are blocked or narrowed, preventing heart attack and relieving symptoms like chest pain, fatigue, palpitations, or shortness of breath. Some patients may be asymptomatic until severe blockage develops.2
Types of CABG:
- Traditional CABG: Open-chest surgery using a heart-lung machine.
- Off-pump CABG: Performed on a beating heart without a heart-lung machine.
- Minimally invasive or robotic-assisted CABG: Small chest incisions, sometimes robot-controlled.3
Preparation:
Patients undergo medical evaluation, blood tests, and consent procedures; must fast 8 hours prior, stop certain medications, and quit smoking to enhance recovery. Allergies, drug history, and cardiac devices should be reported.
Procedure:
The anesthesiologist monitors vital signs and provides anesthesia before placing a breathing tube connected to a ventilator. IV and arterial lines are inserted for medication and monitoring, and a urinary catheter is placed. The surgical site is cleaned, graft vessels are taken from the leg or wrist, and an incision is made in the chest. The sternum is then divided to expose the heart for the bypass procedure.4
Preoperative Examination and Strategy
Before CABG, a full preoperative evaluation assesses overall organ function and graft suitability. Routine tests include chest X-ray, blood count, and kidney and liver function tests. Physical exams check leg veins and perform the Allen test to ensure safe graft harvesting. Anticoagulants like aspirin, clopidogrel, ticagrelor, and warfarin are stopped several days prior to reduce bleeding risk, with heparin used once INR <2.0. After reviewing angiograms, surgeons select target vessels for bypass, most often grafting the left internal thoracic artery (LITA) to the left anterior descending (LAD) artery, which supplies a major portion of the myocardium. Conduits may be used for single or multiple grafts via end-to-side or sequential anastomoses, avoiding excessive harvesting to prevent future complications.5
The intubated patient is brought to the operating room, where peripheral and central lines (e.g., IV and internal jugular) are placed for drug delivery and monitoring before the traditional CABG procedure begins.6
Harvesting the Saphenous Vein and Internal Mammary Artery
While the sternum is opened, graft vessels are harvested—typically the saphenous vein from the leg or the left internal thoracic artery (LITA) from the chest. The LITA is mobilized either as a pedicle (with surrounding tissue) or skeletonized (freed of tissue). Before dividing the LITA distally, heparin is administered to prevent clot formation.7
Catheterization and Cardiopulmonary Bypass
After vessel harvesting, the pericardium is opened, and cannulas are inserted into the aorta and right atrium for cardiopulmonary bypass (CPB). Blood is diverted to a CPB machine for oxygenation, cooled to 32–34 °C to reduce metabolic demand, and a clamp is applied to stop the heart using a potassium-rich cardioplegic solution.8
Anastomosis (Grafting)
With the heart still, distal grafts are placed first—typically to the right coronary and circumflex arteries—followed by the LITA-to-LAD graft. Each anastomosis is checked for patency and leaks before completing proximal grafts on the aorta, avoiding excessive manipulation in atherosclerotic vessels.9
Weaning from Cardiopulmonary Bypass and Closure
After grafting, the aorta and conduits are de-aired, and pacing wires may be applied. Once stable function returns, CPB is discontinued, cannulas are removed, and protamine reverses heparin. Bleeding sites are secured, chest tubes inserted, and the sternum closed.10
Off-Pump CABG
Off-pump coronary artery bypass (OPCAB) avoids the heart-lung machine by stabilizing small heart segments at a time. Careful coordination ensures adequate blood flow while minimizing heart manipulation. Techniques like atrial pacing, pericardial stitches, and snares help maintain exposure and prevent distal ischemia. Distal anastomoses, usually LITA to LAD first, are performed with CO₂ insufflation and sometimes a shunt; proximal grafts are then attached to the aorta. The remainder of the procedure parallels on-pump CABG.11
Procedure Completion (Both Methods)
- Sternum closed with wires.
- Chest tubes inserted for drainage.
- Skin sutured; stomach tube inserted if needed.
- Sterile dressing applied.12
Post-Operative Care
Patients are monitored in the ICU; extubation usually occurs within hours. Discharge typically occurs 4 days post-surgery if stable. Early medications include dobutamine to support cardiac output, beta-blockers for arrhythmia prevention, aspirin to protect grafts, ACE inhibitors/ARBs for blood pressure control, and amlodipine if the radial artery was used.
Grafts
CABG uses arterial or venous conduits. Arterial grafts (e.g., ITA, radial artery) offer superior long-term patency due to endothelial protection but carry higher sternal infection risk in obese or diabetic patients. Veins (mostly saphenous) are practical but have lower patency. Aspirin protects all grafts; adding clopidogrel offers no added benefit.
Comparison with PCI
CABG generally provides better outcomes than PCI in complex lesions, left main disease, diabetic patients, symptomatic patients, and those with impaired LV function.13
Complications
Common complications include bleeding (2–5%), low cardiac output (up to 14%), myocardial infarction (2–5%), arrhythmias (20–40%), neurological deficits (~1.5%), infections (sternal or pulmonary), and GI complications. Risk factors include underlying health conditions and procedural factors.14
Follow-Up and Lifestyle
Post-discharge care includes wound care, suture removal, activity restrictions, and reporting fever, infection, swelling, or unusual symptoms. Lifestyle modifications—smoking cessation, healthy diet, weight management, regular exercise, stress control, and adequate sleep—are crucial for long-term outcomes.15
Summary
Key targets in CABG include reducing graft failure, preventing under-revascularization, and managing atrial fibrillation. Practice gaps persist: multi-arterial grafting (<20%), atrial fibrillation surgery (<50% of eligible patients), and non-sternotomy approaches (<5%). Trials like ROMA, MIST, and STICH3C aim to optimize surgical strategies and patient outcomes.
Author of this article
Professor ATM.Khalilur Rahman,
Professor and Head. Department of Cardiac Anesthesia.
National Heart Foundation & Research Institute, Dhaka.
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