What is Coronary Artery Bypass Grafting (CABG)?

Coronary Artery Bypass Grafting (CABG)

Coronary artery bypass grafting (CABG) is a surgical procedure that improves blood flow to the heart by using blood vessels from other parts of the body to bypass blocked coronary arteries, and remains the standard of care for patients with extensive coronary artery disease. 1

Definition and Overview

• CABG was first introduced in the mid-1960s and evolved rapidly as the standard treatment for patients with extensive coronary artery disease 1
• The procedure involves creating new pathways around significant coronary artery blockages using grafts, most commonly the left internal mammary artery (LIMA) and saphenous vein grafts 2
• Despite the broader use of percutaneous coronary intervention (PCI), CABG continues to be the preferred revascularization strategy for patients with multivessel disease 2

Indications for CABG

Class I Indications (Strong Recommendations)

• Significant left main coronary artery stenosis (>50% diameter) 1
• Left main equivalent disease: significant (≥70%) stenosis of both the proximal left anterior descending (LAD) and proximal left circumflex arteries 1
• Three-vessel coronary disease (survival benefit is greater when left ventricular ejection fraction is <0.50) 1
• Two-vessel disease with significant proximal LAD stenosis and either ejection fraction <0.50 or demonstrable ischemia on noninvasive testing 1
• Unstable angina/non-ST-elevation MI with significant left main coronary artery stenosis or ongoing ischemia not responsive to maximal medical therapy 1

Class IIa Indications (Reasonable to Perform)

• Proximal LAD stenosis with one- or two-vessel disease (becomes Class I if extensive ischemia is documented) 1
• Poor left ventricular function with significant viable noncontracting, revascularizable myocardium 1
• Life-threatening ventricular arrhythmias in the presence of ≥50% left main stenosis and/or triple-vessel disease 1

CABG vs. PCI

• Recent long-term results from the SYNTAX, ASCERT, and FREEDOM trials showed significantly better survival rates after CABG than after PCI 1
• CABG is generally preferred over PCI for patients with:
  • Complex 3-vessel coronary artery disease (SYNTAX score >22) 3
  • Multivessel disease with diabetes mellitus 3
  • Significant left main coronary artery disease in suitable surgical candidates 3

Types of CABG Procedures

Conventional On-Pump CABG

• Traditional approach using cardiopulmonary bypass (CPB) and cardioplegic arrest 1
• Allows for a motionless and bloodless surgical field 4

Off-Pump CABG

• Performed on a beating heart without cardiopulmonary bypass 1, 4
• May reduce morbidity related to CPB, particularly beneficial in high-risk patients 1
• Currently accounts for approximately 20% of CABG procedures in Western countries and the majority in Asia 1
• May reduce the incidence of renal failure, need for intra-aortic balloon pump, and reoperation for bleeding in emergency cases 1

Clampless/Anaortic CABG

• Avoids manipulation of the aorta, which may reduce the risk of stroke 1
• Studies show significantly lower stroke rates with this technique compared to conventional CABG 1
• A meta-analysis of 11,398 patients showed that absence of aortic manipulation was associated with a significant reduction of neurological complications (OR = 0.46) 1

Minimally Invasive CABG

• Includes procedures such as minimally invasive direct coronary artery bypass (MIDCAB) and totally endoscopic coronary artery bypass (TECAB) 1
• MIDCAB is primarily used for isolated LAD stenosis 1
• Hybrid procedures combine MIDCAB (LIMA to LAD) with stenting of other vessels 1
• Benefits include shorter hospital stay, quicker return to work, and higher patient satisfaction 1

Graft Selection

• The left internal mammary artery (LIMA) should be given primary consideration for revascularization of the LAD artery in every patient undergoing CABG 1
• The use of arterial grafts (particularly the LIMA) has significantly improved long-term outcomes 2, 5
• Saphenous vein grafts (SVG) remain the most commonly used conduits despite limitations in long-term patency due to intimal hyperplasia 2
• "No-Touch" harvesting techniques, specific storage solutions, pressure-controlled graft flushing, and external stenting are methods aimed at improving SVG patency 2

Outcomes and Prognosis

• CABG has demonstrated excellent long-term survival rates, with 5-year and 10-year survival of 88.3% and 76.6%, respectively, in minimally invasive procedures 1
• The emphasis in choosing CABG over medical therapy should be preservation of myocardium at risk of infarction as well as relief of angina 6
• Long-term results have improved with better saphenous vein graft preparation, increased use of mammary artery grafts, complete revascularization, use of antiplatelet agents, and control of spasm 6

Complications and Management

• Early postoperative ischemia (<30 days) is typically due to graft occlusion or stenosis 7
• Late postoperative ischemia (>3 years) is most often due to saphenous vein graft lesions 7
• For failed grafts, treatment options include:
  • Percutaneous coronary intervention (PCI) for patent LIMA to LAD with other graft failures 7
  • Repeat CABG for multiple diseased grafts, reduced left ventricular function, or when arterial conduits are available 7

Future Directions

• Increasing adoption of total arterial revascularization to improve long-term outcomes 2
• Continued refinement of minimally invasive and hybrid approaches 1
• Development of better techniques to preserve vein graft patency 2

CABG remains a vital procedure in cardiac surgery with ongoing evolution in techniques and approaches aimed at improving both short-term and long-term outcomes for patients with coronary artery disease.