Cardiothoracic Surgery: Coronary Artery Bypass Graft (CABG)

Coronary Artery Bypass Graft (CABG)

Indications

Basic Procedure

  • Skin Incision (Manubrium to Xiphoid Process)
  • Median Sternotomy
  • Open the Pericardium
  • Harvest the Conduit
    • Surgeon Harvests the Internal Mammary Artery (IMA)
    • Can Have an Assistant Harvest Other Conduits (Radial Artery or Saphenous Vein)
  • Establish Cardiopulmonary Bypass & Cardioplegia
  • Perform the Distal Anastomoses First
  • Perform the Proximal Anastomoses
  • Wean from Cardiopulmonary Bypass
  • Place Chest Tubes:
    • Posterior Pericardium
    • Anterior Mediastinum
    • Bilateral Pleural Cavities
  • Close Sternotomy

Complications

  • Sternal Wound Infection/Mediastinitis
  • Postoperative Bleeding
  • Arrhythmia
    • Most Common Cause of Delayed Discharge After Cardiac Surgery: Atrial Fibrillation
  • Perioperative Myocardial Infarction
  • Low Cardiac Output Syndrome
  • Stroke
  • Renal Dysfunction
  • Mortality
    • 3% Risk Across North America

Cardiopulmonary Bypass (CPB) & Cardioplegia

Cardiopulmonary Bypass (CPB)

  • Definition: Bypasses Cardiopulmonary Circulation from the Right Atrium to the Ascending Aorta
  • “On-Pump” CABG – Uses Cardiopulmonary Bypass with Cardioplegia
    • Standard Technique
    • Benefits:
      • Stabilizes Anastomotic Site with Better Revascularization
      • Motionless Field for Manipulation
      • Provides Myocardial Protection with Cardioplegia
    • Can Induce a Systemic Inflammatory Response & Coagulopathy
  • “Off-Pump” CABG – Does Not Use Cardiopulmonary Bypass
    • Newer Technique
    • Also Known as “Beating Heart” CABG
    • Benefits:
      • Decreased Morbidity & Mortality (Greatest in High-Risk Patient Populations)
      • Decreased Inflammatory Response & Renal Dysfunction
      • Decreased Risk of Stroke
      • Decreased Coagulopathy
    • Overall Considered to Have Inferior Long-Term Outcomes
    • Generally Only Considered in High-Risk Patient Populations That May Not Tolerate Cardioplegia

Cardioplegia

  • Definition: Intentional Induction of Cardiac Arrest During Cardiopulmonary Bypass
  • Provides Myocardial Protection with Reduced Myocardial Oxygen Demand & Cooling to Reduce the Ischemic Effects
    • Also Creates a Motionless & Bloodless Field During “On-Pump” Cardiac Surgery
  • Routes:
    • Anterograde – Administered Through the Proximal Aorta into the Right & Left Coronary Arteries
      • Generally Preferred
    • Retrograde – Administered Through the Right Atrium into the Coronary Sinus
      • Considered for Severe Aortic Regurgitation, Severely Ischemic Patients, LAD is Complete Occlusion or History of Prior CABG with IMA Graft Providing an External Source of Perfusion
  • Many Various Solutions Available
    • Crystalloid-Based or Blood-Based
    • Potassium Chloride (15-35 mEq/L) to Induce Cardiac Arrest
    • Other Possible Inclusions: Magnesium, Calcium, Bicarbonate

Venting

  • Definition: Cannulation of the Aortic Root, Left Ventricular Apex or Pulmonary Artery
  • Prevents Distention from Returning Blood Flow During Cardioplegia
  • Distention Can Be Detrimental to Subsequent Contractility

Conduit & Anastomoses

Conduit Selection

  • Inferior Mammary Artery (IMA)/Internal Thoracic Artery (ITA)
    • Generally the Preferred Conduit – Best Survival
    • Best Patency Rate (90-95% at 20 Years)
    • Collateralizes to Superior Epigastric Artery
  • Greater Saphenous Vein (GSV)
    • The Most Readily Available Conduit & Most Commonly Used
    • Patency:
      • 1-Year: 95%
      • 5-Years: 81-86%
      • 15-Years: 50%
  • Lesser Saphenous Vein
  • Gastroepiploic Artery
  • Radial Artery

Distal Anastomoses

  • Site: The Most Proximal Disease-Free Portion of the Coronary Artery (Immediately After the Most Distal Diseased Portion)
  • Arteriotomy Performed Longitudinally
  • Use 7-0 or 8-0 Prolene
  • May Consider Coronary Endarterectomy with Patch Angioplasty & Bypass Graft for Severe Diffuse Disease if No Anastomotic Site Can Be Found to an Ischemic but Viable Area

Proximal Anastomoses

  • Site: Ascending Aorta
    • In Select Situations May Consider Brachiocephalic Artery, Axillary Artery of Descending Aorta
  • Use 6-0 Prolene