CABG: Coronary Artery Bypass Grafting

Introduction to CABG

• CABG is a surgical procedure that uses grafts to bypass blocked coronary arteries.
• It improves blood flow to ischemic myocardium.
• CABG becomes necessary when severe coronary artery disease (CAD) leads to angina, myocardial infarction (MI), or heart failure.
• Alternatives to CABG include Percutaneous Coronary Intervention (PCI) and medical management.

Basics of Coronary Circulation & Atherosclerosis

• Key coronary arteries: RCA, LCA (LAD, LCX).
• Atherosclerosis pathophysiology involves lipid deposition, plaque formation, and occlusion, leading to ischemia.
• Blockage consequences include stable angina, acute coronary syndrome (ACS), and infarction.

Indications & Patient Selection for CABG

• CABG is indicated for patients with left main coronary artery disease (>50% stenosis), triple vessel disease, failed PCI, or severe angina despite medical therapy.
• Preoperative assessment includes angiography, echocardiography, and stress testing.

Types of CABG

• On-Pump CABG utilizes a Cardiopulmonary Bypass (CPB) Machine.
• In on-pump CABG the heart is arrested with cardioplegia for a bloodless, motionless surgical field.
• Off-Pump CABG (OPCABG) is performed on a beating heart, without CPB.
• OPCABG carries a lower risk of CPB-related complications like stroke and inflammation.
• Minimally Invasive Direct Coronary Artery Bypass (MIDCAB) involves small incisions and no CPB, limited to specific cases.
• Hybrid CABG combines surgical and percutaneous intervention (PCI + CABG).

Cardiopulmonary Bypass (CPB) Machine: Principles & Components

• The CPB machine temporarily takes over heart and lung function during surgery.
• The venous cannula drains deoxygenated blood.
• The oxygenator enriches blood with oxygen.
• A pump (roller or centrifugal) circulates blood.
• The arterial cannula returns oxygenated blood to the body.
• A heat exchanger maintains body temperature.

Cardioplegia: Protecting the Heart During CABG

• Cardioplegia prevents myocardial ischemia by stopping the heart.
• Types of cardioplegia include crystalloid (St. Thomas Solution) and blood cardioplegia (Del Nido, Buckberg Solution).
• Administration can be antegrade or retrograde.
• Strategies address reperfusion injury and myocardial protection.

Surgical Steps of CABG

• The procedure involves anesthesia and a median sternotomy.
• Heparinization and CPB initiation are necessary for on-pump CABG.
• The graft harvesting options are the saphenous vein (leg), internal mammary artery (IMA), or radial artery.
• Graft anastomosis connects the graft proximally to the aorta and distally to the blocked artery.
• Weaning from CPB and reversal of heparin follow.
• Chest closure and postoperative monitoring are the final steps.

Postoperative Care & Complications

• ICU monitoring focuses on hemodynamics, oxygenation, and bleeding.
• Common complications include graft occlusion and arrhythmias (AF).
• Other complications include stroke, renal dysfunction, and wound infections.
• Long-term lifestyle modifications and medications are crucial.

Case 1: CABG in a Patient with Left Main Coronary Artery Disease

• The patient is a 62-year-old male, hypertensive, and diabetic, experiencing exertional chest pain (angina) for 6 months.
• ECG shows ST depressions in leads V4-V6.
• Coronary angiography reveals 90% stenosis in the left main coronary artery (LAD + LCX involvement).
• EF is 50%.
• CABG is preferred over PCI due to the high mortality risk with PCI in left main disease, stemming from potential large myocardial infarction.
• CABG ensures complete revascularization and better long-term survival.
• On-pump CABG is preferred due to extensive disease.
• The surgical plan: Internal mammary artery (IMA) graft to LAD, saphenous vein graft (SVG) to LCX.
• Postoperative care involves ICU monitoring for arrhythmias and bleeding, antiplatelet therapy (Aspirin + Clopidogrel), and long-term lifestyle modifications (diet, exercise, smoking cessation).

Case 2: CABG vs. Off-Pump Surgery in an Elderly Patient

• The patient is a 75-year-old female with a history of chronic kidney disease (CKD) and COPD.
• Presents with unstable angina.
• Angiography demonstrates triple vessel disease, with no left main involvement.
• EF is 40%.
• Off-pump CABG (OPCABG) is preferred to avoid CPB-related complications.
• Grafting plan: LIMA to LAD, SVG to RCA and LCX.
• Perioperative risks include acute kidney injury from contrast-induced nephropathy.
• Strict fluid management and monitoring of renal function are necessary.

Case 3: Emergency CABG Post-Myocardial Infarction

• The patient is a 58-year-old male with acute STEMI, experiencing ongoing chest pain for 4 hours.
• ECG shows ST elevations in leads II, III, aVF.
• Emergency angiography shows complete occlusion of the RCA and 80% stenosis of LAD and LCX.
• Thrombolysis is contraindicated due to recent stroke.
• CABG is safer than PCI due to multivessel disease + recent stroke.
• Initial steps for Immediate stabilization include IV heparin, beta-blockers (if hemodynamically stable), dual antiplatelet therapy.
• The surgical plan encompasses urgent CABG with CPB support. LIMA to LAD, SVG to RCA and LCX.
• Postoperative care includes ICU monitoring for low cardiac output syndrome, arrhythmias, and bleeding.
• Strict BP control prevents anastomotic site rupture.