What is Coronary Artery Bypass Grafting (CABG)?

What is Coronary Artery Bypass Grafting (CABG)?

CABG is a surgical procedure that creates new pathways around blocked coronary arteries using grafts—most commonly the left internal mammary artery (LIMA) and saphenous vein grafts—to restore blood flow to the heart muscle. 1

The Procedure Explained

CABG involves taking a blood vessel from another part of the body (typically the LIMA from the chest wall or a segment of vein from the leg) and grafting it to the coronary arteries to bypass significant blockages. 2 The procedure was first introduced in the mid-1960s and rapidly evolved as the standard treatment for patients with extensive coronary artery disease. 3, 1

Primary Surgical Approaches

Conventional On-Pump CABG is the traditional approach using cardiopulmonary bypass (CPB) with cardioplegic arrest, performed through a median sternotomy that provides access to all coronary territories. 1, 4

Off-Pump CABG is performed on a beating heart without cardiopulmonary bypass and currently accounts for approximately 20% of CABG procedures in Western countries (though the majority in Asia). 1 This technique may reduce morbidity related to CPB, particularly stroke risk (30% relative risk reduction), and is particularly beneficial in high-risk patients. 3, 1

Minimally Invasive CABG (MICS-CABG) is performed via sternotomy-sparing approaches, most commonly through a left minithoracotomy for single-vessel CABG (LIMA to LAD). 5 This approach is associated with reduced blood transfusion rates, surgical site infections, shorter ICU and hospital stays, and faster return to full activity. 5

Which Vessels Are Targeted

The three main coronary arteries targeted in CABG are: 4

• Left Anterior Descending (LAD): The most critical target vessel, supplying the anterior wall and apex of the left ventricle. 4
• Left Circumflex (LCx): The second most important vessel, supplying the lateral wall and sometimes part of the posterior wall. 4
• Right Coronary Artery (RCA): Supplies the right ventricle and inferior wall of the left ventricle. 4

The LIMA to LAD bypass is considered a Class I recommendation (highest level) and should be given primary consideration in every patient undergoing CABG, with long-term patency exceeding 90% at 10 years. 1, 4, 6

When CABG Is Indicated

CABG is recommended for: 1

• Left main coronary artery stenosis >50%
• Three-vessel coronary disease (especially with left ventricular ejection fraction <0.50)
• Two-vessel disease with significant proximal LAD stenosis and either EF <0.50 or demonstrable ischemia
• Complex multivessel disease (SYNTAX score >22) where CABG shows significantly better survival than PCI

For patients with diabetes and multivessel disease, CABG is mandatory over PCI, with substantially amplified mortality benefit. 6

CABG vs. PCI: The Evidence

Recent long-term results from the SYNTAX, ASCERT, and FREEDOM trials showed significantly better survival rates after CABG than after PCI. 3, 1 CABG remains the standard of care for most elective patients with diabetes and/or complex left main or three-vessel disease. 3

Critical Perioperative Management

All patients undergoing CABG should: 2

• Receive aspirin preoperatively and within 6 hours post-surgery to prevent graft thrombosis
• Continue aspirin indefinitely
• Receive beta blockers preoperatively to reduce postsurgical atrial fibrillation
• Be started or continued on high-intensity statin therapy
• Be enrolled in cardiac rehabilitation programs
• Be screened and treated for depression if necessary

Important Caveats

Avoid CABG within 3-7 days of acute MI unless there is ongoing ischemia with hemodynamic compromise, as surgical mortality is elevated during this window. 6 However, emergency CABG is indicated for life-threatening ventricular arrhythmias or cardiogenic shock within 18 hours of onset. 6

Off-pump CABG carries a risk of reduced graft patency compared to on-pump procedures, with some studies showing 27% higher risk of graft occlusion at 1 year. 3 This must be weighed against the reduced stroke risk.

Saphenous vein grafts have declining patency over time (25-50% at 10-15 years), with high early failure rates (10-26% between 12-18 months) especially when used for distal targets and severely diseased small vessels. 4