coronary artery bypass grafting (CABG)

Introduction

Vein or artery grafted surgically to permit blood to travel from the aorta to a branch of the coronary artery at a point past an obstruction.

Indications

• recurrent myocardial ischemia (unstable angina) secondary to coronary artery disease
  • not anatomically appropriate for PTCA (PCI)
• coronary artery disease with mechanical complications that require surgical repair
  • mitral regurgitation
  • ventricular septal rupture
• myocardial infarction
  • urgent CABG for failed PCI or thrombolytic therapy after STEMI, includes patients with diabetes mellitus
  • with impaired left ventricular function
  • 2 or more coronary vessels with > 50% stenosis
  • viable left ventricular myocardium with abnormal wall motion
• stable angina
  • with normal left ventricular function
  • significant left main coronary artery disease
  • proximal left anterior descending artery disease & proximal left circumflex artery disease
    • >= 70% stenosis
  • 3-vessel disease or severe 2-vessel disease
• coronary artery disease in patients with diabetes mellitus
• CABG is recommended for patients with
  • left main disease
  • triple vessel disease & reduced systolic function
  • multivessel disease with involvement of the proximal left anterior descending artery in the presence of diabetes

CABG improves survival in patients with:

• left main coronary artery disease (appears controversial)
  • either PCI or CABG reasonable for left main coronary artery disease
• three vessel disease &
  • moderate left ventricular dysfunction, or
  • myocardial ischemia at low workloads
• multivessel disease with involvement of proximal left anterior descending artery (LAD)

CABG improves quality-of-life for up to 36 months in patients with ischemic left ventricular dysfunction

Contraindications

• Caution: (Risk factors)
  • age
  • female sex
  • poor left ventricular function
  • left main coronary artery disease
  • unstable angina
  • diabetes mellitus
• CABG does NOT prevent myocardial infarction
• CABG does NOT reduce incidence of ventricular arrhythmias

Advantages

• CABG is indicated for patients with diabetes mellitus who would otherwise be eligible for PTCA (better 5 year survival, 80% vs 65%)
• CABG is superior to PTCA (PCI) for patients > 65 years of age

Benefit/risk

• number needed to treat (NNT)
  • 25 to prevent 1 death within 10 years
  • 10-14 to prevent 1 non-fatal MI within 10 years
• number needed to harm
  • 83 to cause 1 death
  • 100 to cause 1 non-fatal stroke
  • 43 to cause 1 case of renal failure
  • 3-5 to cause 1 case of cognitive impairment
  • 14 cases of extended life support
  • 28 patients need reoperation

Laboratory

• elevation of markers of myocardial infarction after bypass associated with increased mortality at 1 year
  • serum creatine kinase MB
  • serum troponin I

Procedure

• saphenous vein graft*
• radial artery graft*
• internal thoracic artery graft
• bilateral & single internal thoracic artery graft grafts with no difference in mortality in patients with multivessel disease

* compared saphenous vein graft, radial artery graft for CABG associated with lower rate of adverse cardiac events (RR=0.67) & a lower rate of occlusion at 5 years (RR=0.44)

Radiology

• myocardial perfusion imaging to assess myocardial viability have not uniformly shown which patients will benefit from CABG

Complications

• cognitive impairment
  • short term (53% at hospital discharge)
  • long-term (24% at 6 months, 42% at 5 years)
  • use of cardiopulmonary bypass pump a factor
    • no difference on or off bypass pump, 50% at 5 years
  • strongest predictor of postoperative cognitive decline is preoperative cognitive impairment
  • risk of cognitive impairment after CABG, PCI or cardiac valve replacement is uncertain
• delirium after CABG is associated with increassed mortality
• pulmonary complications common
  • pneumonia, atelectasis, pleural effusion, ventilator dependence
  • inspiratory muscle training daily for 2 weeks prior to CABG reduces pulmonary complications
• harvesting of veins for coronary artery bypass grafting
  • wound infection
  • postoperative pain
  • vein graft failure
  • subclavian steal (internal mammary artery)
• endoscopic harvesting with higher rate of composite of death, MI, & revascularization (3 year hazard ratio, 1.22) than open harvesting
• bilateral vs single internal thoracic artery grafting associated with early excess of sternal wound complications
• accelerated idioventricular rhythm (ventricular tachycardia) is common following coronary reperfusion & does not require intervention when it occurs within the 1st 24 hours
• new-onset post-operative atrial fibrillation
  • anticoagulation indicated
  • long-term risk of thromboembolic stroke
    • < preoperative atrial fibrillation (RR=0.67)
    • ~ same as no post-CABG atrial fibrillation (RR=1.11)
    • 15 year RR=0.55 vs no anticoagulation
• infection
  • invasive infection with Mycobacterium chimaera due to contamination of heater-cooler devices*
• graft aneurysm

* LivaNova's Stockert 3T heater-cooler devices used to help regulate blood temperature during bypass surgert in 60% of bypass surgeries in the U.S.

Management

• discontinuation of aspirin prior to CABG (4 days) neither beneficial or harmful
• aspirin administration during 1st 48 hours after CABG reduces in hospital mortality
• tight glycemic control (serum glucose 90-120 mg/dL) increases the incidence of hypoglycemic events & does not result in any significant improvement in clinical outcomes relative to moderate glycemic control (serum glucose 120-180 mg/dL)
• cardiac stress testing (stress echocardiography) after CABG may be appropriate
• preoperative beta-blocker is not associated with improved outcomes in patients without recent myocardial infarction
• statin use (equivalent of >= 20 mg atorvastatin) within 24 hours before CABG associated with reduced 30-day mortality (1.7% vs 3.8% for no statin use within 72 hours)
• routine electrocardiogram, cardiac stress testing or angiography (invasive or CT angiography) in asymptomatic patients after successful CABG not indicated
• aspirin (81 mg) + clopidogrel, ticagrelor or prasugrel indicated for 12 months after CABG in patients with MI or acute coronary syndrome
• aspirin or clopidogrel after CABG in patients with stable chronic angina pectoris
• ticagrelor alone superior to aspirin alone, but non-inferior to ticagrelor + aspirin, in patients undergoing elective CABG with saphenous vein graft (1 year graft patency)
• delay non-cardiac surgery for at least 30 days after CABG
• aspirin + ticagrelor associated with reduced risk for venous graft failure (RR=0.5); same for aspirin + clopidogrel (RR=0.6)

Notes

• CABG provides relief from angina
• closure rate on saphenous vein grafts are 20% at 1 year
• CABG superior to PCI for severe coronary artery disease
• off-pump vs on pump CABG
  • better outcomes & graft patency for on pump CABG
  • no significant advantage of off-pump vs on pump CABG
  • overall mortality 50% lower for on-pump versus off-pump CABG

More general terms

• cardiac surgery (heart surgery)
• arterial bypass graft; bypass surgery
• coronary artery revascularization

More specific terms

• minimally invasive direct coronary artery bypass (MIDCAB)

Additional terms

• Bypass Angioplasty Revascularization Investivation (BARI)
• coronary stent/coronary stenting
• percutaneous coronary intervention (PCI)
• percutaneous coronary intervention (PCI)/coronary stent vs CABG

Patient information

coronary artery bypass grafting (CABG) patient information