Coronary artery bypass grafting

Coronary artery bypass grafting (or CABG) is a cardiac revascularization technique used to treat patients with significant, symptomatic stenosis of the coronary artery (or its branches). The stenosed segment is bypassed using an arterial (e.g., internal thoracic artery) or venous (e.g., great saphenous vein) autograft, re-establishing blood flow to the ischemic areas of the myocardium. This may be performed either with the help of a heart-lung bypass machine (traditional CABG, performed via a thoracotomy), or on a beating heart (off-pump CABG, and minimally invasive direct CABG). In addition to general surgical risks, the main complications associated with bypass grafting are bypass occlusion and postpericardiotomy syndrome. The procedure provides more effective symptom relief than medical management and is superior to PCI in multivessel coronary disease.

Indication for CABG is established after careful consideration of the clinical features, coronary catheterization findings, cardiac function, and the patient's general condition.

• High-grade left main stem coronary artery stenosis
• Significant stenosis (> 70%) of the proximal left anterior descending artery, with 2-vessel or 3-vessel disease
• Symptomatic 2-vessel or 3-vessel disease
• Disabling angina despite maximal medical therapy
• Poor left ventricular function with myocardium that can return to function on revascularization
• Postinfarct angina
• Indications for emergency CABG
  • Non-ST segment elevation myocardial infarction with ongoing ischemia that is unresponsive to medical therapy/PCI
  • STEMI with inadequate response to all nonsurgical therapy
  • Significant ongoing ischemia, traumatic complications, or threatened occlusion in STEMI, after a failed PCI or previous CABG

There are no absolute contraindications for CABG. Relative contraindications include:

• Asymptomatic patients with a low risk of myocardial infarction or death
• Comorbidities (e.g., COPD, pulmonary hypertension, systemic diseases)
• Advanced age ^[1]

We list the most important contraindications. The selection is not exhaustive.

• Overview of steps
  • Thoracotomy via a midline sternotomy → cardiopulmonary bypass; (heart-lung machine) → cardioplegic arrest of the heart → anastomosis of the bypass vessels distal to the coronary artery stenosis using autologous vessels
• Types of grafts
  • Arterial graft
    • Internal thoracic artery (internal mammary artery)
      • Good accessibility, close proximity to the heart
      • Left thoracic artery is suitable for bridging stenoses in the left anterior descending artery due to their close spatial proximity.
    • Radial artery: performance modified Allen test before CABG
  • Venous graft (aortocoronary saphenous vein bypass, or ACVB)
    • Great saphenous vein (first choice in vein bypass grafts because of good surgical access to the long, superficial leg vein with suitable vessel cross-section)
    • Small saphenous vein
• Types of CABG
  • Traditional CABG
  • Off-pump coronary artery bypass (OPCAB) surgery
  • Minimally invasive direct, or totally endoscopic CABG
• Alternate procedure: percutaneous coronary intervention (PCI)
  • Advantages: decreased periprocedural morbidity, decreased cost, decreased hospital stay
  • Disadvantages: higher rate of patients requiring reintervention
  • CABG is proven to be a superior long-term form of revascularization in high-risk multivessel disease (diabetics or low LV function), certain cases of severe two-vessel CAD, and in all patients with three-vessel CAD.
  • PCI is preferred in cases with symptomatic low-risk obstruction (single vessel, mild double vessel obstruction).

Postoperative long-term treatment with antiplatelet drugs (e.g., 100 mg aspirin 1-0-0) is required to reduce the risk of subsequent myocardial ischemia.

Cardiac complications

• Myocardial dysfunction
• Postpericardiotomy syndrome: autoimmune febrile pericarditis or pleuritis that may occur 1–6 weeks following cardiac surgery
  • Features
    • Fever, malaise
    • Chest pain, with or without associated dyspnea
    • Tachycardia
    • Pericardial friction rub
  • Treatment
    • Anti-inflammatory drugs: nonsteroidal anti-inflammatory drugs (NSAIDs) or prednisone
    • Pericardial drainage
    • Surgery: formation of a pericardial window through thoracotomy or by means of a balloon catheter
• Postoperative cardiac tamponade with cardiogenic shock
• Bypass occlusion
• Arrhythmias

Mediastinal complications

• Postoperative acute mediastinitis
• Mediastinal hemorrhage
  • Features: excessive blood (> 100–200 mL per hour) in chest tube drainage; decreased cardiac output, hemoglobin, blood pressure, or urine output; chest x-ray shows mediastinal widening
  • Treatment: raising the airway pressure for artificial ventilation; surgical exploration of the mediastinum

Other

• Complications resulting from sternotomy (e.g., wound infection, sternal dehiscence, sternal osteomyelitis)
• Postoperative renal failure
• Neurologic deficits and coma

References:^[2]

We list the most important complications. The selection is not exhaustive.

• Prognosis following CABG depends on a variety of factors, such as anatomical location and severity of the stenoses, presence of comorbidities, patient age, and preoperative levels of activity.
• Successful grafts typically last 8–15 years and provide an improved chance of survival (decreased 5-year mortality, especially in patients with triple vessel disease).
• Further progression of arteriosclerosis may still occur after CABG.