Coronary artery bypass grafting (CABG) is indicated in patients with (1) chronic stable angina and high-risk vessel disease; (2) unstable angina; (3) post-MI angina; and (4) atypical symptoms and ischemia on noninvasive testing. Anatomical indications for CABG include triple-vessel disease, left main coronary artery stenosis > 50%, severe proximal vessel stenosis > 70%, and left anterior descending or left circumflex artery stenosis in the presence of left ventricular dysfunction.
CABG is not indicated for asymptomatic coronary artery disease (CAD) patients at low risk for myocardial infarction (MI) or death, or for individuals who lack viable myocardium. If the affected coronary artery is too small for grafting or vessel harvesting is estimated to be inadequate, CABG should not be attempted. Advanced age, due to comorbidities and increased functional decline, may place patients at higher risk for perioperative complications.
CABG is performed through a median sternotomy incision. Following incision and cardiac exam, vessel harvesting for grafting commences. Common vessels for grafting include the internal thoracic (mammary) arteries, radial arteries, or saphenous veins. Once vessels have been chosen and removed, the patient undergoes preparation for cardiopulmonary bypass (CPB).
CPB redirects deoxygenated venous blood away from the right atrium (RA), removing carbon dioxide, introducing oxygen, and then returning oxygenated blood to the ascending aorta or less commonly to one of the femoral arteries. CPB permits temporary diversion of blood flow from the heart and lungs to an extracorporeal circuit, thereby providing a functionally similar means of ventilation and perfusion while rendering the heart bloodless for vessel grafting surgery.
For anticoagulation, heparin administered prior to cannulation prevents thrombosis in the patient and in the CPB circuit. After 3 minutes, an activated coagulation time (ACT) measurement ensures appropriate anticoagulation has been achieved.
Once the patient is anticoagulated, the surgical team proceeds with vascular cannulation. Cannulation provides access for the CPB circuit to remove deoxygenated blood from venous circulation and return oxygenated blood to arterial circulation.
Conventionally, arterial cannulation is performed first to provide a conduit for volume resuscitation should it be required. The ascending aorta is the preferred site for arterial cannulation, given ease of access and minimal dissection risk, and additional incision is not required. Alternatively, a femoral, iliac, or axillary artery may be used if aortic cannulation is contraindicated due to severe atherosclerosis.
Venous cannulation is accomplished with a single atrial cannula via drainage holes in the RA only, cavoatrial cannula with drainage holes in the RA and IVC, or with bicaval cannula via drainage holes in the IVC and SVC. Single ...