Coronary Artery Bypass Grafting 

Updated: Oct 30, 2017
Author: Rohit Shahani, MD, MS, MCh; Chief Editor: Karlheinz Peter, MD, PhD 

Overview

Practice Essentials

Coronary artery bypass grafting (CABG) is performed for patients with coronary artery disease (CAD) to improve quality of life and reduce cardiac-related mortality.

Indications

Class I indications for CABG from the American College of Cardiology (ACC) and the American Heart Association (AHA) are as follows[1, 2] :

  • Over 50% left main coronary artery stenosis

  • Over 70% stenosis of the proximal left anterior descending (LAD) and proximal circumflex arteries

  • Three-vessel disease in asymptomatic patients or those with mild or stable angina

  • Three-vessel disease with proximal LAD stenosis in patients with poor left ventricular (LV) function

  • One- or two-Vessel disease and a large area of viable myocardium in high-risk area in patients with stable angina

  • Over 70% proximal LAD stenosis with either an ejection fraction (EF) below 50% or demonstrable ischemia on noninvasive testing

Other indications for CABG include the following:

  • Disabling angina (class I)

  • Ongoing ischemia in the setting of a non–ST segment elevation myocardial infarction (MI) that is unresponsive to medical therapy (class I)

  • Poor LV function but with viable, nonfunctioning myocardium above the anatomic defect that can be revascularized

CABG may be performed as an emergency procedure in the context of an ST-segment elevation MI (STEMI) in cases where it has not been possible to perform percutaneous coronary intervention (PCI) or where PCI has failed and there is persistent pain and ischemia threatening a significant area of myocardium despite medical therapy.

Contraindications

CABG is not considered appropriate in asymptomatic patients who are at a low risk of MI or death. Patients who will experience little benefit from coronary revascularization are also excluded.

Although advanced age is not a contraindication, CABG should be carefully considered in the elderly, especially those older than 85 years. These patients are also more likely to experience perioperative complications after CABG. A multidisciplinary heart team approach that emphasizes shared decision making in patients with complex CAD is essential to offer the patient the best chance of a successful revascularization strategy.

Preprocedural evaluation

Before performing CABG, clinicians should carefully examine the patient’s medical history for factors that might predispose to complications, such as the following:

  • Recent MI

  • Previous cardiac surgery or chest radiation

  • Conditions predisposing to bleeding

  • Renal dysfunction

  • Cerebrovascular disease including carotid bruits and transient ischemic attack (TIA)

  • Electrolyte disturbances that might predispose the patient to dysrhythmias

  • Infection, including urinary tract infection and dental abscesses

  • Respiratory function, including the presence of chronic obstructive pulmonary disease (COPD) or infection[3]

Routine preoperative investigations include the following[3] :

  • Full blood count (abnormalities corrected)

  • Clotting screen

  • Creatinine and electrolyte levels (abnormalities corrected and discussed with the anesthetist)

  • Liver function tests

  • Screening for methicillin-resistant Staphylococcus aureus (MRSA)

  • Chest radiography

  • Electrocardiography (ECG)

  • Echocardiography or ventriculography (to assess LV function)

  • Coronary angiography (to define the extent and location of CAD)

Assessment of Risk

Risk models to predict 30-day mortality following isolated CABG is an active area of research. Risk models such as the Euroscore system,[4] and the Society of Thoracic Surgeons (STS) 2008 Cardiac Surgery Risk Model,[5]  are the most commonly used predictors in cardiac surgery. Shared variables in these two impressive models include age, previous MI, peripheral vascular disease (PVD), renal failure, hemodynamic state and EF. In the STS model, 78% of the variance is explained by eight of the most important variables, which include age, surgical acuity, reoperative status, creatinine level, dialysis, shock, chronic lung disease, and EF.

Premedication

The aims of premedication are to minimize myocardial oxygen demands by reducing heart rate and systemic arterial pressure and to improve myocardial blood flow with vasodilators. Drugs that should be continued up to the time of surgery are as follows:

  • Beta-blockers, calcium channel blockers, and nitrates

  • Aspirin

Administered agents are as follows:

  • Temazepam immediately preoperatively

  • Midazolam, a small intravenous (IV) dose in the operating room before arterial line insertion

Each patient should be cross-matched with 2 units of blood (for simple cases) or 6 units of blood, fresh frozen plasma, and platelets (for complex cases).[3, 6, 7] Tranexamic acid (1-g bolus before surgical incision followed by an infusion of 400 mg/hr during surgery) may be considered to reduce the amount of postoperative mediastinal bleeding and the quantity of blood products used (ie, red blood cell and fresh frozen plasma)[8]

Anesthesia

Cardiac surgery is most commonly performed under deep general endotracheal anesthesia.

Rarely used adjuncts make use of the following two forms of neuraxial blockade:

  • Intrathecal opioid infusion

  • Thoracic epidural anesthesia (generally a low-dose local anesthetic/opioid infusion)

Monitoring

In addition to the standard anesthetic monitoring (ECG, pulse oximetry, nasopharyngeal temperature, urine output, gas analysis), specific monitoring requirements for cardiac surgery include the following:

  • Invasive blood pressure

  • Central venous access

  • Transesophageal echocardiography (TEE)

  • Neurologic monitoring

  • Monitoring of bilateral cerebral saturations

  • Pulmonary artery pressure monitoring with a Swan-Ganz catheter

Technique

Sites from which the conduit can be harvested include the following:

  • Saphenous vein

  • Left internal thoracic (mammary) artery (LITA)

  • Radial artery

  • Right internal thoracic (mammary) artery (RITA)

  • Right gastroepiploic artery

  • Inferior epigastric artery

  • Short saphenous vein

  • Cephalic vein and upper extremity vein

The usual incision used for CABG is a midline sternotomy (see the image below), although an anterior thoracotomy for bypass of the LAD or lateral thoracotomy for marginal vessels may be used when an off-pump procedure is being performed. Cardiopulmonary bypass, cardioplegic arrest, and placement of the graft follows.

Illustration of a median sternotomy. Illustration of a median sternotomy.

Alternative approaches to CABG include the following:

  • Off-pump CABG

  • Minimally invasive direct CABG (MIDCAB)

  • Totally endoscopic CABG

  • Hybrid technique (bypass plus stenting)

  • Robotic-assisted CABG

Background

Coronary artery bypass grafting (CABG) is performed for patients with coronary artery disease (CAD) to improve quality of life and reduce cardiac-related mortality. CAD is the leading cause of mortality in the United States[9] and the developed world,[10] and 16.5 million US adults (age ≥20 years) are affected by this disease annually.[9]  It alone accounts for 530,989 deaths each year in the United States, and the long-term manifestations of CAD with left ventricular dysfunction and heart failure are projected to affect over 8 million people aged at least 18 years by 2030.[9]

CABG was introduced in the 1960s with the aim of offering symptomatic relief, improved quality of life, and increased life expectancy to patients with CAD.[11, 12] By the 1970s, CABG was found to increase survival rates in patients with multivessel disease and left main disease when compared with medical therapy.[13]

The new paradigm for treatment of CAD calls for a heart team approach that involves the cardiologist and the cardiac surgeon evaluating the coronary angiogram together and offering the best possible option to the patient to achieve coronary revascularization, whether it be placement of a percutaneous coronary stent or CABG. At present, the typical patient for CABG is older, is more likely to have undergone previous percutaneous coronary intervention (PCI), and has significantly more comorbidities. Despite these adverse risk factors, CABG continues to be one of the most important surgical procedures in the history of modern medicine and probably has prolonged more lives and provided more significant symptomatic relief than any other major operation in medicine. New less-invasive options, advancement in anesthetic and intensive care unit (ICU) management, and technological advances are pushing the boundaries of this procedure to new heights.

Historical information

Alexis Carrel received the Nobel prize in physiology and medicine for his work in 1912. His understanding of the association between angina pectoris and coronary artery stenosis allowed him to anastomose a carotid artery segment to the left coronary artery from the descending thoracic aorta in canine model.[14]

In the late 1940s, the famous Canadian surgeon Arthur Vineberg implanted the left internal thoracic (mammary) artery, directly into the myocardium of the anterior left ventricle in patients with severe angina pectoralis.[15, 16, 17] Surprisingly, this procedure produced significant symptomatic relief in a few patients.[18]

In 1962, Sabiston, at Duke University, performed the first planned saphenous vein bypass operation for coronary revascularization.[19]  In 1964, Kolessov used the left internal thoracic (mammary) artery to bypass the left anterior descending artery without cardiopulmonary bypass,[20] and, in 1973, Carpentier introduced the use of radial artery grafts as conduits for CABG.[21, 22]

In the 1970s and early 1980s, CABG flourished as the sole therapy for CAD.  With the advent, introduction, and widespread adoption of percutaneous coronary artery stenting in the 1980s and 1990s there was a decline in the number of CABG operations performed. However, several multicenter studies comparing CABG with current stent therapy have clearly demonstrated the superiority of CABG, especially when certain patient characteristics such as diabetes, multivessel CAD and ischemic cardiomyopathy are taken into account.

Indications

Coronary artery bypass grafting (CABG) is performed for both symptomatic and prognostic reasons. Indications for CABG have been classified by the American College of Cardiology (ACC) and the American Heart Association (AHA) according to the level of evidence supporting the usefulness and efficacy of the procedure[1, 2] :

  • Class I: Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective

  • Class II: Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness or efficacy of a procedure or treatment

  • Class IIa: Weight of evidence or opinion is in favor of usefulness or efficacy

  • Class IIb: Usefulness or efficacy is less well established by evidence or opinion

  • Class III: Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful or effective, and in some cases it may be harmful

Indications for CABG as detailed by the ACC and the AHA are listed in Table 1 below.

Table 1. ACC/AHA Indications for Coronary Artery Bypass Grafting [1, 2] (Open Table in a new window)

Indication

Asymptomatic or Mild Angina

Stable Angina

Unstable Angina/ NSTEMI

Poor Left Ventricular Function

Left main stenosis >50%

Class I

Class I

Class I

Class I

Stenosis of proximal LAD and proximal circumflex artery >70%

Class I

Class I

Class I

Class I

3-Vessel disease

Class I

Class I

 

Class I, with proximal LAD stenosis

2-Vessel disease

 

Class I if there is a large area of viable myocardium in a high-risk area;

Class IIa if there is a moderate viable area and ischemia

Class IIb

 

With >70% proximal LAD stenosis

Class IIa

Class I with either an ejection fraction < 50% or demonstrable ischemia on noninvasive testing

Class IIa

Class I

Involving proximal LAD

Class IIb

 

 

 

1-Vessel disease

 

Class I if there is a large area of viable myocardium in a high-risk area;

Class IIa, if there is a viable moderate area and ischemia

Class IIb

 

With >70% proximal LAD stenosis

Class IIa

Class IIa

Class IIa

 

Involving proximal LAD

Class IIb

 

 

 

ACC = American College of Cardiology; AHA = American Heart Association; LAD = left anterior descending (artery); NSTEMI = non–ST-segment elevation myocardial infarction.

 

Alexander and Smith in the New England Journal of Medicine noted the following indications for CABG are associated with a survival benefit over medical therapy, with or without percutaneous coronary intervention (PCI) include[23] :

  • Acute ST-segment elevation myocardial infarction (STEMI)

  • CAD other than acute STEMI

  • Coronary anatomy not amenable to PCI

  • Mechanical complications, such as ventricular septal defect, rupture of the free ventricular wall, or papillary-muscle rupture with severe mitral regurgitation

  • Left main disease of 50% stenosis or greater, and intermediate or high complexity for PCI (Synergy Between PCI with TAXUS and Cardiac Surgery [SYNTAX] score ≥33)

  • Three-vessel disease of 70% stenosis or greater, involving the LAD and intermediate or high complexity for PCI (SYNTAX score ≥23)

Other indications for CABG include the following:

  • Disabling angina (Class I)

  • Ongoing ischemia in the setting of a non-ST segment elevation myocardial infarction (NSTEMI) that is unresponsive to medical therapy (Class I)

  • Poor left ventricular function but with viable, nonfunctioning myocardium above the anatomic defect that can be revascularized

  • Clinically significant CAD of 70% stenosis or greater, in 1 or more vessel(s), and refractory angina despite medical therapy and PCI[23]

  • Clinically significant CAD of 70% stenosis or greater, in 1 or more vessel(s), in survivors of sudden cardiac arrest presumed to be related to ischemic ventricular arrhythmia[23]

  • Clinically significant CAD of 50% stenosis or greater, in 1 or more vessel(s), in patients undergoing cardiac surgery for other indications (eg, valve replacement or aortic surgery)[23]

CABG may be performed as an emergency procedure in the context of a STEMI in cases where it has not been possible to perform PCI or where this procedure has failed and there is persistent pain and ischemia threatening a significant area of the myocardium despite medical therapy.

Other indications for CABG in the setting of STEMI are ventricular septal defect related to MI, papillary muscle rupture, free wall rupture, ventricular pseudoaneurysm, life-threatening ventricular arrhythmias, and cardiogenic shock.

Factors that increase the survival benefit of CABG include the following[23] :

  • Left ventricular ejection fraction of 45% or less

  • Diabetes mellitus

  • Ischemic mitral regurgitation

  • PCI failure, with or without acute MI (AMI)

Indications for CABG when PCI is noninferior to CABG and when PCI or CABG is preferred over medical therapy include the following[23] :

  • Left main disease of 50% stenosis or greater, and low-to-intermediate complexity for PCI (SYNTAX score ≤32)

  • Three-vessel disease of 70% stenosis or greater, and low complexity for PCI (SYNTAX score ≤22)

  • Two-vessel disease of 70% stenosis or greater, involving the LAD and low complexity for PCI (SYNTAX score ≤22)

Factors that increase the benefit of PCI over CABG include the following[23] :

  • Elevated mortality risk with CABG
  • Elevated stroke risk
  • Extreme frailty
  • Prior CABG
  • Acute STEMI at presentation

 

Table 2 below shows the recommendations for treatment of patients with acute heart failure in the setting of AMI.

Table 2. Treatment Recommendations for Patients with Acute Heart Failure in Setting of Acute Myocardial Infarction (Open Table in a new window)

 

Class of Recommendation

Level of Evidence

Patients with NSTE-ACS or STEMI and unstable hemodynamics should immediately be transferred for invasive evaluation and target vessel revascularization

Class I

A

Immediate reperfusion is indicated in acute heart failure with ongoing ischemia

Class I

B

Echocardiography should be performed to assess LV function and to exclude mechanical complications

Class I

C

Emergency angiography and revascularization of all critically narrowed arteries by PCI/CABG as appropriate is indicated in patients in cardiogenic shock

Class I

B

IABP insertion is recommended in patients with hemodynamic instability (particularly those in cardiogenic shock and with mechanical complications)

Class I

C

Surgery for mechanical complications of AMI should be performed as soon as possible with persistent hemodynamic deterioration despite IABP

Class I

B

Emergency surgery after failure of PCI or fibrinolysis is indicated only in patients with persistent hemodynamic instability or life-threatening ventricular arrhythmia due to extensive ischemia (left main or severe 3-vessel disease)

Class I

C

If the patient continues to deteriorate without adequate cardiac output to prevent end-organ failure, temporary mechanical assistance (surgical implantation of LVAD/BiVAD) should be considered

Class IIa

C

Routine use of percutaneous centrifugal pumps is not recommended

Class III

B

AMI = acute myocardial infarction; BiVAD = biventricular assist device; CABG = coronary artery bypass grafting; IABP = intra-aortic balloon pump; LV = left ventricle; LVAD = left ventricular assist device; NSTE-ACS = non–ST-segment elevation acute coronary syndrome; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction.

 

Special recommendations in patients with comorbidities are presented in the tables below.

Table 3. Specific Treatment Recommendations for Coronary Artery Disease in Patients with Mild to Moderate Chronic Kidney Disease (Open Table in a new window)

 

Recommendation

Level of Evidence

CABG should be considered, rather than PCI, when the extent of CAD justifies a surgical approach, the patient’s risk profile is acceptable, and the life expectancy is reasonable

Class IIa

B

Off-pump CABG may be considered rather than on-pump CABG

Class IIb

B

For PCI, disease-eluting stents may be considered, rather than bare metal stents

Class IIb

C

CABG = coronary artery bypass grafting; CAD = coronary artery disease; PCI = percutaneous coronary intervention.

  Table 4. Specific Treatment Recommendations for Coronary Artery Disease in Diabetic Patients (Open Table in a new window)

 

Recommendation

Level of Evidence

In patients presenting with STEMI, primary PCI is preferred over fibrinolysis if it can be performed within recommended time limits

Class I

A

In stable patients with extensive CAD, revascularization is indicated to improve MACCE-free survival

Class I

A

Use of drug-eluting stents is recommended to reduce restenosis and repeat target vessel revascularization

Class I

A

In patients on metformin, renal function should be carefully monitored after coronary angiography/PCI

Class I

C

CABG should be considered, rather than PCI, when the extent of CAD justifies a surgical approach (especially multivessel disease) and the patient’s risk profile is acceptable

Class IIa

B

In patients with known renal failure undergoing PCI, metformin may be stopped 48 hours before the procedure

Class IIb

C

Systematic use of glucose insulin potassium in diabetic patients undergoing revascularization is not indicated

Class III

B

CABG = coronary artery bypass grafting; CAD = coronary artery disease; MACCE = major adverse cardiac and cerebral event; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction.

  Table 5. Recommendations for Combining Valve Surgery and Coronary Artery Bypass Grafting (Open Table in a new window)

 

Recommendation

Level of Evidence

In combination with valve surgery:

CABG is recommended in patients with a primary indication for aortic/mitral valve surgery and coronary artery stenosis = 70%

Class I

C

CABG should be considered in patients with a primary indication for aortic/mitral valve surgery and coronary artery stenosis of 50-70%

Class IIa

C

In combination with CABG:

Mitral valve surgery is indicated in patients with a primary indication for CABG and severe ischemic mitral regurgitation and an EF >30%*

Class I

C

Mitral valve surgery should be considered in patients with a primary indication for CABG and moderate ischemic mitral regurgitation, provided that valve repair is feasible and performed by experienced operators

Class IIa

C

Aortic valve surgery should be considered in patients with a primary indication for CABG and moderate aortic stenosis (mean gradient 30-50 mm Hg, Doppler velocity of 3-4 m/sec, or heavily calcified aortic valve even with Doppler velocity of 2.5-3 m/sec)

Class IIa

C

* Definition of severe mitral regurgitation is at http://www.escardio.org/guidelines.

CABG = coronary artery bypass grafting; EF = ejection fraction.

  Table 6. Carotid Revascularization in Patients Scheduled for Coronary Artery Bypass Grafting (Open Table in a new window)

 

Recommendation

Level of Evidence

CEA or CAS should be performed only by teams with demonstrated 30-day combined death-stroke rates of < 3% in patients without previous neurologic symptoms and < 6% in patients with previous neurologic symptoms

Class I

A

Indication for carotid revascularization should be individualized after discussion by a multidisciplinary team, including a neurologist

Class I

C

Timing of procedures (synchronous or staged) should be dictated by local expertise and clinical presentation, with the most symptomatic territory targeted first

Class I

C

In patients with previous TIA/nondisabling stroke:

Carotid revascularization is recommended for 70-99% carotid stenosis

Class I

C

Carotid revascularization may be considered for 50-69% carotid stenosis in men with symptoms of < 6 months

Class IIb

C

Carotid revascularization is not recommended if carotid stenosis is < 50% in men and < 70% in women

Class III

C

In patients with no previous TIA/stroke:

Carotid revascularization may be considered in men with bilateral 70-99% carotid stenosis or 70-99% carotid stenosis and contralateral occlusion

Class IIb

C

Carotid revascularization is not recommended in women or patients with a life expectancy < 5 years

Class III

C

CAS = carotid artery stenting; CEA = carotid endarterectomy; TIA = transient ischemic attack.

  Table 7. Management of Patients with Associated Coronary and Peripheral Arterial Disease (Open Table in a new window)

 

Recommendation

Level of Evidence

In patients with unstable CAD, vascular surgery is postponed and CAD treated first, except when vascular surgery cannot be delayed because of a life-threatening condition

Class I

B

Beta-blockers and statins are indicated preoperatively and should be continued postoperatively in patients with known CAD who are scheduled for high-risk vascular surgery

Class I

B

The choice between CABG and PCI should be individualized and assessed by the heart team taking into account the patterns of CAD, PAD, comorbidity, and clinical presentation

Class I

C

Prophylactic myocardial revascularization before high-risk vascular surgery may be considered in stable patients if they have persistent signs of extensive ischemic or high cardiac risk

Class IIb

B

CABG = coronary artery bypass grafting; CAD = coronary artery disease; PAD = peripheral arterial disease; PCI = percutaneous coronary intervention.

  Table 8. Management of Patients with Renal Artery Stenosis (Open Table in a new window)

 

Recommendation

Level of Evidence

Functional assessment of renal artery stenosis severity using pressure gradient measurements may be useful in selecting hypertensive patients who may benefit from renal artery stenting

Class IIb

B

Routine renal artery stenting to prevent deterioration of renal function is not recommended

Class III

B

  Table 9. Recommendations for Patients with Chronic Heart Failure and Systolic Left Ventricular Dysfunction (Ejection Fraction = 35%), Presenting Predominantly with Angina Symptoms (Open Table in a new window)

 

Recommendation

Level of Evidence

CABG is recommended for the following:

  • Significant left main stenosis

  • Left main equivalent (proximal stenosis of both left anterior descending and left circumflex)

  • Proximal left anterior descending stenosis with 2- or 3-vessel disease

Class I

B

CABG with surgical ventricular reconstruction may be considered in patients with LVESV index = 60 mL/m2 and scarred left anterior descending territory

Class IIb

B

PCI may be considered in the presence of viable myocardium if the anatomy is suitable

Class IIb

C

CABG = coronary artery bypass grafting; LVESV = left ventricular end-systolic volume; PCI = percutaneous coronary intervention.

  Table 10. Recommendations for Patients with Chronic Heart Failure and Systolic Left Ventricular Dysfunction (Ejection Fraction = 35%), Presenting Predominantly with Heart Failure Symptoms (No or Mild Angina: Canadian Cardiovascular Society 1-2) (Open Table in a new window)

 

Recommendation

Level of Evidence

LV aneurysmectomy during CABG is indicated in patients with a large LV aneurysm

Class I

C

CABG should be considered in the presence of viable myocardium, irrespective of the LVESV

Class IIa

B

CABG with SVR may be considered in patients with scarred LAD territory

Class IIb

B

PCI may be considered in the presence of viable myocardium if the anatomy is suitable

Class IIb

C

Revascularization in the absence of evidence of myocardial viability is not recommended

Class III

B

CABG = coronary artery bypass grafting; LAD = left anterior descending (artery); LV = left ventricle; LVESV = left ventricular end-systolic volume; PCI = percutaneous coronary intervention; SVR = surgical ventricular reconstruction.

Contraindications

Coronary artery bypass grafting (CABG) carries a risk of morbidity and mortality and is therefore not considered appropriate in asymptomatic patients who are at a low risk of myocardial infarction or death. Patients who will experience little benefit from coronary revascularization are also excluded.

CABG is performed in elderly patients for symptomatic relief. Although advanced age is not a contraindication, CABG should be carefully considered in the elderly, especially those older than 85 years. These patients are also more likely to experience perioperative complications after CABG. A multidisciplinary heart team approach that emphasizes shared decision making in patients with complex coronary artery disease is essential to offer the patient the best chance of a successful revascularization strategy.

Technical Considerations

Best practices

Either arteries or veins may be used as conduits for coronary artery bypass grafting (CABG). The survival benefits of grafting the left internal thoracic (mammary) artery to the left anterior descending coronary artery was established many years ago in a landmark paper from the Cleveland Clinic.[24]  This remains true; in fact, bilateral internal thoracic (mammary) artery grafting, if possible, confers a significant long-term survival benefit. Robust evidence suggests that the use off an additional arterial graft rather than a vein graft is associated with further improvement in late outcomes.[25] The greater saphenous vein and, very rarely, the short saphenous vein are the most commonly used vein grafts, whereas the internal thoracic (mammary) artery is the most commonly used artery graft. The radial artery graft was reintroduced into clinical practice in the 1990s and continues to show high patency rates of 80% or higher at 10 years follow-up, especially if the target vessel stenosis was greater than 90%.[26]

The disadvantage of saphenous vein grafts is their declining patency with time: 10-20% are occluded 1 year after surgery because of technical errors, thrombosis, and intimal hyperplasia.[1] Another 1-2% of vein grafts occlude every year from 1-5 years after surgery, and 4-5% occlude every year from 6-10 years after surgery. Vein graft occlusion that occurs 1 or more years after CABG is due to vein graft atherosclerosis with developing neointimal hyperplasia.. At 10 years after surgery, only 50-60% of saphenous vein grafts are patent, and only half of these are free of angiographic atherosclerosis.[1] As part of appropriate secondary prevention, patients should receive life-long antiplatelet therapy, most commonly with daily low-dose (81 mg) aspirin.

Unlike saphenous vein grafts, internal thoracic (mammary) artery grafts exhibit stable patency over time.[1] At 10 years, more than 90% of internal thoracic (mammary) artery grafts are patent. The left internal thoracic (mammary) artery should be the conduit used when the left anterior coronary artery is bypassed.

Technical recommendations for CABG are presented in Table 11 below.

Table 11. Technical Recommendations for Coronary Artery Bypass Grafting (Open Table in a new window)

 

Recommendation

Level of Evidence

Procedures should be performed in a hospital structure and by a team specialized in cardiac surgery, using written protocols

Class I

B

Arterial grafting to the LAD system is indicated

Class I

A

Complete revascularization with arterial grafting to a non-LAD coronary system is indicated in patients with a reasonable life expectancy

Class I

A

Minimization of aortic manipulation is recommended

Class I

C

Graft evaluation is recommended before departure from the operating theater

Class I

C

LAD = left anterior descending (artery).

Procedure planning

The formation of a multidisciplinary heart team enables a balanced decision-making process (see Table 12 below).[27, 28] Clinicians should approach the informed consent process as an opportunity to enhance objective decision-making rather than solely as a legal requirement. It is vital to be aware that factors such as sex, race, availability, technical skills, local results, referral patterns, and patient preference may affect the decision-making process independent of clinical findings.[27]

Table 12. Multidisciplinary Decision Pathways, Patient Informed Consent, and Timing of Intervention [27] (Open Table in a new window)

 

 

Acute Coronary Syndrome 

 

Stable Multivessel Disease

Stable with Indication for Ad Hoc PCI

 

Shock

STEMI

NSTE-ACS

Other ACS

Multidisciplinary decision making

Not mandatory

Not mandatory

Not required for culprit lesion but required for nonculprit vessel(s)

Required

Required

According to predefined protocols

Informed consent

Oral witnessed informed consent or family consent if possible without delay

Oral witnessed informed consent may be sufficient unless written consent is legally required

Written informed consent* (if time permits)

Written informed consent*

Written informed consent*

Written informed consent*

Time to revascularization

Emergency: No delay

Emergency: No delay

Urgency: Within 24 h if possible and no later than 72 h

Urgency: Time constraints apply

Elective: No time constraints

Elective: No time constraints

Procedure

Proceed with intervention on basis of best evidence/ availability

Proceed with intervention on basis of best evidence/availability

Proceed with intervention on basis of best evidence/ availability; nonculprit lesions treated according to institutional protocol

Proceed with intervention on basis of best evidence/ availability; nonculprit lesions treated according to institutional protocol

Plan most appropriate intervention, allowing enough time from diagnostic catheterization to intervention

Proceed with intervention according to institutional protocol defined by local heart team

* May not apply to countries that legally do not ask for written informed consent, although European Society of Cardiology and European Association for Cardiothoracic Surgery strongly advocate documentation of patient consent for all revascularization procedures.

ACS = acute coronary syndrome; NSTE-ACS = non–ST-segment elevation acute coronary syndrome; PCI = percutaneous coronary intervention; STEMI = ST-segment elevation myocardial infarction.

Additional input from general practitioners, anesthesiologists, geriatricians, and intensivists may be needed.

Hospitals without a surgical cardiac unit or with interventional cardiologists working in an ambulatory setting should refer to standard evidence-based protocols devised in collaboration with expert interventional cardiologists and cardiac surgeons or should seek the opinions of these physicians for complex cases. Consensus on the best revascularization treatment should be documented. Standard protocols that are in accordance with current guidelines may be used to obviate individual case review of each diagnostic angiogram.

Ad hoc PCI is a therapeutic interventional procedure that is performed directly after the diagnostic procedure rather than during a different session.[27] Although it is convenient and often cost-effective, ad hoc PCI is not desirable for all cases; some patients may be in categories for which CABG is the most suitable choice. The anatomic criteria and clinical factors that determine whether a patient can or cannot be treated by means of ad-hoc PCI should be defined by institutional protocols designed by the heart team.[27]

Complication prevention

Cerebrovascular complications are a major cause of morbidity after CABG. The main causes of these complications are hypoperfusion or embolic events. Accordingly, it is important to maintain adequate mean arterial pressures as a prophylactic measure against hypoperfusion, although there is little that can be done to protect the patient from embolic events.

Outcomes

In patients with multivessel coronary disease, coronary artery bypass grafting (CABG), as compared with percutaneous coronary intervention (PCI), leads to a reduction in long-term mortality and myocardial infarctions (MIs) as well as reductions in repeat revascularizations, regardless of whether patients are diabetic are not, according to a meta-analysis of six randomized clinical trials comprising 6055 patients from the era of arterial grafting and stenting.[29]

In a meta-analysis of eight randomized studies that included a total of 3612 adult patients with diabetes and multivessel coronary artery disease (CAD), treatment with CABG significantly reduced the risk of all-cause mortality by 33% at 5 years, as compared with PCI. This relative risk reduction did not differ significantly when patients who underwent CABG were compared with subgroups of patients who received either bare metal stents or drug-eluting stents.[30, 31]

In a study of 3723 patients with multivessel coronary disease that compared whether the effect on survival from PCI (n = 1097) compared with CABG (n = 5626) is related to the age of the patient, Benedetto et al found that CABG resulted in a significant reduction in late-phase mortality across all age groups compared to PCI.[32] At a mean follow-up of 5.5 ± 3.2 years, there were 301 deaths overall (PCI: 208; CABG: 93). Overall survival for the PCI group was 95% at 1 year, 84% at 5 years, and 75% at 8 years compared to 95% at 1 year, 92.4% at 5 years, and 90% at 8 years for the CABG group.[32]

In a retrospective (1997-2013), nationwide, population-based Swedish study that evaluated long-term survival, major adverse cardiovascular events, and factors associated with elevated risk in 4086 young adults (≤50 years) undergoing CABG, Dalen et al found better outcomes in younger adults than their older counterparts.[33] At a median follow-up of 10.9 years, 490 (12%) patients died, with 96% survival at 5 years, 90% at 10 years, and 82% at 15 years. The survival of patients aged 51 to 70 years and those older than 70 years who underwent CABG during the same period was significantly worse. The primary risk factors for all-cause mortality were chronic kidney disease, reduced left ventricular ejection fraction, peripheral vascular disease, or chronic obstructive pulmonary disease.[33]

Results of the Surgical Treatment for Ischemic Heart Failure (STICH) Extension Study (STICHES), which evaluated the long-term, 10-year outcomes of CABG in 1212 patients with ischemic cardiomyopathy and an ejection fraction of 35% or less, concluded that the rates of death from any cause, death from cardiovascular causes, and death from any cause or hospitalization for cardiovascular causes were significantly lower in patients who underwent CABG and received medical therapy than among those who received medical therapy alone.[34]

In single-center retrospective analysis (2003-2013) of 763 elderly patients (age ≥75 years) with multivessel disease who underwent PCI or CABG within 30 days of the index catherization, CABG was associated with the best overall clinical outcomes.[35] However, only 20% of the patients (n = 150) underwent CABG. The best treatment strategy for this population remains to be determined.[35]

Similarly, results from analysis of 2007-2014 data from the National Cardiovascular Data Registry Acute Coronary Treatment and Intervention Outcomes Network Registry-Get With The Guidelines that evaluated trends in CABG utilization and in-hospital outcomes showed that CABG was used infrequently in 15,145 patients with ST-segment elevation myocardial infarction (STEMI) during the index hospitalization, with CABG rates declining over time.[36]  In addition, there was a wide hospital-level variation in CABG rates in STEMI, and CABG was generally performed within 1-3 days following angiography. In-hospital mortality rates were similar for patients who underwent CABG and those who did not.[36]

In a meta-analysis of comparison of 5-year outcomes of PCI with drug-eluting stents versus CABG in 6637 patients with unprotected left main CAD from nine studies over a 14-year period (2003-2016), PCI with drug-eluting stents was associated with equivalent cardiac and all-cause mortality but lower rates of stroke and higher rates of repeat revascularization.[37] A trend favoring CABG over PCI for major adverse cardiac and cerebrovascular events did not reach statistical significance.

With regard to quality of life following CABG compared with PCI for multivessel CAD, both interventions provide improvements in the frequency of angina.[38] However, at 1 month postprocedure, PCI patients appear to recover faster and have improved short-term health status compared to patients who undergo CABG, whereas at 6 months and longer postprocedure, CABG patients appear to have greater angina relief and improved quality of life relative to those who undergo PCI.[38]

Future Directions

Despite a steady increase in the proportion of older and higher risk patients being referred for surgery, major perioperative morbidity and mortality continues to be low, and long-term outcomes are excellent. With an operation that has stood the test of time, future advances in percutaneous coronary interventions (PCIs), molecular therapeutics, and novel surgical approaches must be rigorously compared to the gold standard of coronary artery bypass grafting (CABG).

Current mortality risk prediction models for CABG do not have a standardized approach to defining outcome and predictor variables, and they include problematic issues such as inadequate sample sizes, inappropriate handling of missing data, as well as suboptimal statistical techniques.[39] Future risk modelling will need to improve upon these factors to refine the quality of mortality risk prediction.

The surgical robot allows surgeons to remotely manipulate fully articulating videoscopic instruments by way of "master-slave" servos and microprocessor control. The improved video resolution is an advantage, but the added expense and time required as well as difficulty with learning this technique, in addition to the limited applications in CABG surgery, has limited the role of robotic-assisted CABG.

A relatively recent development is hybrid surgical and percutaneous revascularization. In this approach, patients undergo not only minimally invasive CABG, most often with the use of the left internal thoracic (mammary) artery graft to the left anterior descending coronary artery, but also undergo PCI of lesions in the circumflex and right coronary arteries. This strategy provides the benefits of CABG with a lower morbidity and could emerge as the new standard for patients with multivessel coronary artery disease (CAD).[40, 41]

CABG does not prevent the progression of native CAD, however, both disease progression and vein graft failure can be ameliorated by aggressive secondary prevention with medical therapy.[42] The American Heart Association recommends life-long antiplatelet therapy.[43]  Daily intake of low-dose (81 mg) aspirin may be preferable to minimize the risk of bleeding. Beta blockers should be used in patients with recent myocardial infarction, left ventricular systolic dysfunction, or in patients with non-revascularized CAD. All patients, regardless of their lipid values should receive life-long high-intensity statin therapy. Diet, exercise, and smoking cessation are well known adjuncts to promote improved cardiovascular health.[43]

 

Periprocedural Care

Preprocedural Evaluation

Before performing coronary artery bypass grafting (CABG), clinicians should carefully examine the patient’s medical history for factors that might predispose to complications, such as the following:

  • Recent myocardial infarction (MI)

  • Previous cardiac surgery or chest radiation

  • Conditions predisposing to bleeding

  • Renal dysfunction

  • Cerebrovascular disease including carotid bruits and transient ischemic attack (TIA)

  • Electrolyte disturbances that might predispose the patient to dysrhythmias

  • Infection including urinary tract infection, skin infections, and dental abscesses

  • Respiratory function including the presence of chronic obstructive pulmonary disease or infection[3]

The Euroscore is one of several scoring systems used to predict CABG mortality. Results can be rendered logistically or as a simple score, which can be calculated by using the Euroscore interactive calculator.[4]

Routine preoperative investigations include the following[3] :

  • Full blood count (abnormalities corrected)

  • Clotting screen

  • Creatinine and electrolyte levels (abnormalities corrected and discussed with the anesthetist)

  • Liver function tests

  • Screening for methicillin-resistant Staphylococcus aureus

  • Chest radiography

  • Electrocardiography (ECG)

  • Echocardiography or ventriculography (to assess left ventricular [LV] function)

  • Coronary angiography (to define the extent and location of coronary artery disease [CAD])

A raised white blood cell (WBC) count should prompt a careful examination for any cause of infection. If possible, CABG should be postponed until infection has been excluded or treated. If the patient’s demographic characteristics (eg, age or smoking) indicate an increased risk of cancer, a gastrointestinal or urinary tract malignancy should be excluded.

The initial CABGs in the 1960s were performed “off pump” (OPCABG) because of the lack of cardiopulmonary bypass technology.[44] With the subsequent development of safe and effective cardiopulmonary bypass, most CABGs are now performed “on pump” (ONCABG). However, the off-pump approach has been reintroduced, with varying degrees of popularity, in an effort to reduce the complications associated with cardiopulmonary bypass. The surgical experience of the operating surgeons performing the OPCABG is critical to the outcome of the procedure. In a Cochrane review that analyzed 86 randomized trials involving 10,716 patients, Moller and colleagues reported that OPCABG resulted in increased all-cause mortality compared to ONCABG (3.7% vs 3.1%; P = 0.04), but there were no significant differences in MI, stroke, renal insufficiency, or coronary artery reintervention between the two techniques other than that OPCABG resulted in fever distal anastomoses.[45]

Elderly patients who have major comorbid conditions (eg, previous stroke or TIA; peripheral vascular disease [PVD]; bleeding disorders; or current respiratory, liver, or renal disease) may benefit from an off-pump approach. The off-pump approach may also be preferred in patients with a heavily calcified or atheromatous aorta, where cannulation is associated with a high risk of stroke.[46]

Assessment of Risk

Risk models to predict 30-day mortality following isolated CABG is an active area of research. Risk models such as the Euroscore system,[4] and the Society of Thoracic Surgeons (STS) Cardiac Surgery Risk Model,[5]  are the most commonly used predictors in cardiac surgery. Shared variables in these two impressive models include age, previous MI, PVD, renal failure, hemodynamic state, and ejection fraction (EF). In the STS model, 78% of the variance is explained by eight of the most important variables, which include age, surgical acuity, reoperative status, creatinine level, dialysis, shock, chronic lung disease, and EF.

Patient Preparation

Premedication

The aims of premedication are to minimize myocardial oxygen demands by reducing heart rate and systemic arterial pressure and to improve myocardial blood flow with vasodilators.

Before the advent of coronary artery bypass grafting (CABG), the majority of patients with coronary artery disease (CAD) received beta-adrenoceptor blocking drugs and calcium channel antagonists or nitrates. These drugs were continued until the point of surgery because sudden withdrawal of the medications could cause tachycardia, rebound hypertension, and a loss of coronary vasodilatation.

Administration of temazepam immediately before CABG can decrease the risk of tachycardia and hypertension resulting from anxiety regarding the procedure. In the operating room, intravenous (IV) administration of a small dose of midazolam before arterial line insertion can also reduce anxiety, tachycardia, and hypertension.

In patients referred for CABG, aspirin should be continued up to the time of surgery, especially in those who present with an acute coronary syndrome (ACS). In patients receiving a thienopyridine (eg, clopidogrel or prasugrel) in whom elective CABG is planned, the drug should be withheld if possible for either 5 days (for clopidogrel) or 7 days (for prasugrel) before the procedure.

Each patient should be cross-matched with 2 units of blood (for simple cases) or 6 units of blood, fresh frozen plasma, and platelets (for complex cases).[3, 6, 7] Tranexamic acid (1-g bolus before surgical incision followed by an infusion of 400 mg/hr during surgery) may be considered to reduce the amount of postoperative mediastinal bleeding and the quantity of blood products used (ie, red blood cell and fresh frozen plasma)[8]

Antidepressant treatment for 2-3 weeks before undergoing CABG and continued for 6 months afterward may foster a faster postoperative mental health recovery and have a beneficial effect on postoperative pain.[47, 48]

Anesthesia

After standard monitoring equipment is attached and peripheral venous access is achieved but before the arterial line is inserted, the midazolam dose is administered. Before placement of the arterial line, ensure that a radial artery graft will not be used for CABG.

During induction and tracheal intubation, it is important to maintain a steady heart rate and blood pressure. Thus, patients should be preoxygenated. Induction of anesthesia is accomplished with high doses of an opioid (usually fentanyl or remifentanil) to minimize the dose of propofol, etomidate, or thiopental, and thereby maximize cardiovascular stability. Although etomidate usually does not cause changes in blood pressure, it may induce hypotension in cardiac patients.

A number of agents may be used for muscle relaxation. However, they each have their own associated complications, as follows:

  • Pancuronium increases myocardial oxygen demand

  • Vecuronium may cause bradycardia in association with opioids

  • Rocuronium can cause tachycardia

  • Atracurium (which is not considered suitable for operations of long duration) can cause hypotension secondary to histamine release

The trachea should be intubated orally because nasal intubation may cause significant bleeding once heparin is administered. A double-lumen endotracheal tube is required if CABG is being performed via a left thoracotomy.

Central venous access should be obtained, as it is not uncommon for the patient to become hypotensive. To ensure that there is sufficient diastolic pressure to maintain coronary perfusion, hypotension should be treated with IV fluids or with an alpha agonist if left ventricular function is depressed.

Typically, maintenance of anesthesia is accomplished with an opioid infusion (fentanyl, alfentanil, sufentanil, or remifentanil) combined with either a propofol infusion (total IV anesthesia) or a volatile agent. Volatile agents are generally carried in an air-oxygen mixture because the use of nitrous oxide as a carrier is controversial. Isoflurane may have a myocardial protective effect and is therefore especially useful in off-pump surgery.

Positioning

For a standard sternotomy, the anterior thorax is exposed with the patient in a supine position. A roll is placed in the interscapular region to improve access to the sternum by extending the neck and elevating the sternal notch. Usually the sterile field extends from the chin to the toes to include the sternotomy incision as well as access to the saphenous veins for harvesting as a conduit. If the radial artery is being used as a conduit, the appropriate arm is also prepped into the sterile field.

Monitoring and Follow-up

In addition to the standard anesthetic monitoring (electrocardiography [ECG], pulse oximetry, nasopharyngeal temperature, urine output, and gas analysis), there are a number of specific monitoring requirements for cardiac surgery, including the following:

  • Invasive blood pressure

  • Central venous access

  • Transesophageal echocardiography (TEE)

  • Neurologic monitoring

  • Pulmonary artery pressure monitoring with a Swan-Ganz catheter

  • Cerebral oxygen saturation monitors bilaterally

Accurate and rapidly updated blood pressure measurements are required during cardiac anesthesia. Generally, the radial artery of the nondominant hand is cannulated, although the right radial artery should be used if the patient requires additional aortic surgery or insertion of an intra-aortic balloon pump (IABP). Care should be taken to ensure that radial grafts will not be used for bypass conduits in the procedure.

Central venous access is required for administering vasoactive drugs, inserting a transverse pacing wire (if indicated), monitoring central venous pressure, and passing a pulmonary artery catheter.

TEE is often useful during coronary artery bypass grafting (CABG) to assess left ventricular (LV) function, determine the presence of mitral valve insufficiency, and evaluate the patient who is difficult to wean from cardiopulmonary bypass. TEE is now almost universally accepted as a standard of care for major intraoperative monitoring.

Neurologic monitoring is regularly used in CABG, but no monitoring device enables accurate and easy identification of potential neurologic damage (a complication in 1-3% of patients). Available monitors include electroencephalography (EEG), transcranial Doppler ultrasonography, jugular venous bulb oxygen saturation, and near-infrared spectroscopy for monitoring cerebral oxygen saturation.

After CABG, transport the patient to a dedicated cardiac surgery intensive care unit (SICU). If the patient’s condition is uncomplicated, basic management and progress assessment include the following:

  • During the first 6-12 hours after CABG, there is usually a decline in myocardial function secondary to a number of factors, including myocardial edema and ischemia-reperfusion injury. If this occurs, the patient may require increased inotropic support or pacing. However, most patients can be weaned from inotropic support within 24 hours after the operation, and the temporary epicardial pacing wires can be removed at around 3 days.

  • In the early postoperative period, a continuous infusion of nitroglycerin should be administered if a radial graft has been used, because such grafts are prone to spasm in the period immediately following the operation, resulting in myocardial ischemia.

  • Although many patients can be extubated in the first 6 hours following CABG, the majority are not extubated until postoperative day 1.

  • The patient’s temperature should be carefully regulated. Some patients may have peripheral vasodilation and hypotension secondary to an elevated body temperature arising from difficulties in central thermoregulation. This hypotension is associated with a worse neurologic outcome.

  • There is usually a 1 mL/kg/h diuresis immediately after CABG as a consequence of the amount of fluid administered intraoperatively. The urinary catheter can be removed once the patient is mobile. Oral furosemide can be used postoperatively, if needed. If LV function is preserved and the patient’s weight has returned to baseline, diuretic therapy can usually be discontinued late in the first postoperative week.

  • Drainage from the mediastinum should gradually decrease over the first 6 hours after CABG. The mediastinal drains often can be removed on postoperative day 1 when there has been no drainage for 3 consecutive hours. After their removal, a chest radiograph should be taken.

  • Ideally, patients should be sitting in a chair on postoperative day 1 and should be mobilized as soon as possible.

Also note the following:

  • In the first 6 hours after CABG, many patients require increased insulin. Lactulose and senna can be used as a laxative from day 1. Patients are encouraged to drink fluids and ingest an advancing diet after extubation and confirmation of normal mental status. Shortly thereafter, insulin sliding scales can be stopped and normal antihyperglycemic drugs started.

  • A prophylactic dose of 75 mg of aspirin once daily by mouth should be commenced in the first 6 hours after the procedure. Statins should be started on postoperative day 1. Low-molecular-weight heparin and antiembolism stockings should be used for prophylaxis of deep vein thrombosis; the stockings have the added benefit of reducing edema in the saphenous donor leg.[49]

  • In the absence of epidural analgesia, patient-controlled analgesia should be used for pain relief once the patient has been extubated. It is usually required for only 2-3 days postoperatively, by which time orally administered analgesia typically provides sufficient pain relief.

 

Technique

Approach Considerations

The goal of coronary artery bypass grafting (CABG) is complete revascularization of the area of the myocardium that is perfused by coronary arteries with a luminal stenosis of more than 50%. Several methods may be used for this purpose. A durable conduit is vital for successful CABG. There are a number of sites from which the conduit can be harvested, including the following:

  • Saphenous vein

  • Radial artery

  • Left internal thoracic (mammary) artery (LITA)

  • Right internal thoracic (mammary) artery (RITA)

  • Right gastroepiploic artery

  • Inferior epigastric artery

Harvesting of the Conduit

Saphenous vein

The great (long) saphenous vein (GSV) is located 2 cm anterior to the medial malleolus, traverses the tibia, and ascends posteriorly up the tibial border before emptying into the femoral vein. It receives numerous tributaries, notably at the knee, and contains 10-20 valves. Key associated structures are the saphenous nerve, femoral cutaneous nerve, and saphenous branch of the genicular artery. The small (short) saphenous vein (SSV) is located 1 cm posterior to the lateral malleolus, runs centrally up the posterior calf, and drains into the popliteal vein.

As coronary artery bypass grafting (CABG) conduits, the saphenous veins have an 80-90% early patency rate, which decreases to 50% at 10 years. The saphenous vein is generally acceptable as a conduit in the absence of other vascular pathologies in the leg (varicosities in the vein, venous insufficiency, previous deep vein thrombosis [DVT], or small lumen diameter) or overlying infection.

The GSV can be procured either via an open harvest technique (see the image below), starting from either the ankle or groin and using a vein stripper, or via an endoscopic technique. Likewise, the SSV vein can be harvested either with an open procedure or endoscopically.

Published experience comparing open vein harvest (OVH) with endoscopic vein harvest (EVH) suggests decreased wound-related complications, improved patient satisfaction, shorter hospital stay, and reduced postoperative pain at the harvest site following EVH.[50]  Vein trauma is minimized by constant visualization, proper countertraction, and careful hemostasis.The available evidence predominantly confirms that EVH is no worse than OVH at short- and mid-term follow-up.

Illustration of the open saphenous vein harvest te Illustration of the open saphenous vein harvest technique.

 

The legs and groin should be shaved, prepared, and draped in the operating room. Care should be taken to avoid getting skin preparation solution on the diathermy plate; this can result in diathermy burns. Once the anesthetist is ready for surgery to start and the surgeon has confirmed the number of lengths (25 cm) of vein required, the vein harvest can begin.

Internal thoracic (mammary) artery

The left internal thoracic (mammary) artery (LITA) and the right internal thoracic (mammary) artery (RITA) arise from their respective subclavian arteries. The internal thoracic (mammary) artery can be harvested either by itself or as a pedicle (see the figure below).

Illustration of an internal thoracic (mammary) art Illustration of an internal thoracic (mammary) artery (IMA) harvest as a pedicle.

 

Whereas the LITA is most commonly harvested as a pedicle, the RITA is generally skeletonized, because an RITA pedicle may interfere with sternal wound healing. The LITA is useful in left anterior descending (LAD) artery anastomosis and has a good patency rate in this setting (98% at 1 year and 90% at 10 years). The RITA has a good patency rate when anastomosed to the LAD (96% at 1 year and 90% at 5 years) but a reduced rate when grafted to the circumflex or the right coronary artery (75% at 1 year).

Coronary Artery Bypass

The usual incision for coronary artery bypass grafting (CABG) is a midline sternotomy (see the image below), although an anterior thoracotomy for bypass of the left anterior descending (LAD) artery or a lateral thoracotomy for marginal vessels may be used when an off-pump procedure is being performed.

Illustration of a median sternotomy. Illustration of a median sternotomy.

 

CABG with cardiopulmonary bypass and cardioplegic arrest is demonstrated in the video below.

This video demonstrates coronary artery bypass grafting with cardiopulmonary bypass and cardioplegic arrest. Video courtesy of Dale K Mueller, MD.

Cardiopulmonary bypass

The first step in cardiopulmonary bypass is to cannulate the aorta and right atrium. The aortic area selected for cannulation must be soft and nonatherosclerotic. To insert the aortic cannula, unfractionated heparin is given, and the systolic blood pressure is lowered to below 100 mm Hg. At this point, two purse-string sutures are placed into the aorta, and the aortic adventitia within the diameter of the purse-string sutures is divided. An aortotomy is performed with a scalpel, the cannula is placed, and the purse-string sutures are tightened around it.

The aortic cannula is then secured to a rubber tourniquet with a heavy silk tie. Once in place, the cannula is de-aired and connected to the arterial pump tubing, where its position in the aorta can be confirmed by watching the pattern of tube filling. The venous cannula is inserted into the right atrial appendage in a similar fashion, with the end of the cannula positioned in the inferior vena cava. Adequate anticoagulation is confirmed by assessing the activated clotting time; once this is done, cardiopulmonary bypass can be commenced.

The aorta is cross-clamped distal to the cannula, and cold cardioplegia solution is infused via the aortic cannula (some centers also cool the patient). Retrograde cardioplegia may also be administered via the coronary sinus, especially in the patient who is undergoing repeat CABGs and has few or no patent grafts for adequate perfusion with antegrade cardioplegia. Compared with crystalloid cardioplegia, blood cardioplegia is associated with a lower incidence of intraoperative mortality, postoperative myocardial infarction, shock, and conduction defects.

Placement of graft

After the initiation of cardiopulmonary bypass, the distal coronary bypass targets are identified. As a rule, anastomoses to the right coronary artery and the marginal branches of the circumflex artery are completed first.

The circumflex argery is accessed by retracting the heart laterally, whereas the posterior descending artery and posterolateral circulation are accessed by retracting the heart cephalically. The left internal thoracic (mammary) artery (LITA) is then usually anastomosed to the LAD if possible. In rare circumstances (eg, CABG performed for acute anterior myocardial infarction), a saphenous vein graft may be placed to the LAD artery for expediency.

To accomplish the bypass, an incision is made in the distal coronary artery, and the conduit ostium is sutured around the full circumference of the anastomosis (see the image below). The conduit is then infused with cold cardioplegia solution, and the end is tied with a polypropylene suture. A very fine monofilament suture, commonly 7-0 or 8-0, is used to complete the distal coronary anastomosis. Most often, it is an end-to-side anastomosis as shown in the picture below. Often ,we can construct a side-to-side anastomosis when a sequential anastomosis was performed with the same conduit.

Illustration of the distal anastomotic technique. Illustration of the distal anastomotic technique.

 

When all the distal anastomoses are completed, rewarming of the heart is initiated, the aortic cross-clamp is removed, and a partially occluding clamp is placed on the ascending aorta where the grafts are to be anastomosed. Holes are punched in the ascending aorta, secured by the partially occluded clamp, and the proximal ends of the anastomoses are sutured into place in the aorta (see the image below). Before the cross-clamp is finally removed, air is evacuated from the grafts and ascending aorta. The patient is then weaned off the bypass.

Illustration of the proximal anastomotic technique Illustration of the proximal anastomotic technique.

 

When normal rhythm is resumed, the patient is once again mechanically ventilated and electrolyte abnormalities (commonly hypomagnesemia and hypokalemia) are corrected. If the patient is bradycardic or experiences temporary heart block, temporary pacing is performed using wires placed to the right atrium and right ventricle. When cardiopulmonary bypass has been successfully stopped, protamine is given to reverse the heparin.[51]

Alternative Approaches to Coronary Artery Bypass Grafting

Off-pump CABG

The key to off-pump coronary artery bypass grafting (OPCABG) is the maintenance of blood pressure, heart rate, and normothermia (with the use of warming blankets). Preload must be optimized during manipulation of the heart to minimize hemodynamic instability. A number of techniques can be used to prevent hypotension, including prophylactic intravenous (IV) fluid infusion, use of the Trendelenburg and reverse Trendelenburg positions, and low-dose alpha-agonist infusion.[52]

A systematic review did not demonstrate any significant benefit of (OPCABG) compared with on-pump CABG (ONCABG) regarding mortality, stroke, or myocardial infarction.[53]

Totally endoscopic CABG

Endoscopic surgical techniques with robotic assistance were developed to enable the performance of surgery in difficult spaces; they are widely used across most surgical disciplines. The specific application of these techniques to the treatment of coronary artery disease (CAD) is known as totally endoscopic CABG. Totally endoscopic CABG, which aims to decrease postoperative morbidity, duration of hospital stay, and overall cost, allows surgeons to perform endoscopic surgery on both the beating and arrested heart.[54]

The first step in totally endoscopic CABG is to deflate the lung. Next, three small incisions are made at the intercostal spaces, through which one robotic arm with an attached endoscope and two arms carrying surgical accessories are passed. These arms are controlled by the operator from a unit located away from the operating table. Grafts are then harvested from suitable sites, and an anastomosis is completed across the affected coronary artery.[55]

Hybrid technique

Advances in surgical techniques and introduction of drug-eluting stents have provided a platform for a hybrid combined strategy that involves grafting the left anterior descending artery with the left internal thoracic (mammary) artery and then stenting the other coronary territories with drug-eluting stents instead of bypassing them with saphenous vein grafts.

Although preliminary data indicate that such a hybrid strategy may be a reasonable alternative for some patients with multivessel coronary artery disease, the real clinical utility of this approach will not be known until results of randomized clinical trials are available.

Complications

A number of complications are associated with coronary artery bypass grafting (CABG), both in the short term and in the long term; they are associated with anesthesia, cardiopulmonary bypass, sternotomy, and the operation itself. These complications may include the following:

  • Myocardial dysfunction

  • Cerebrovascular complications

  • Acute renal failure

  • Cardiac tamponade

  • Respiratory tract infections

  • Aortic dissection

In the initial postoperative period, there is a decline in myocardial function secondary to myocardial edema and ischemia-reperfusion injury. Additional factors (eg, incomplete revascularization and postoperative graft failure) may exacerbate the dysfunction. Patients may exhibit a low-output syndrome, with 4-9% requiring the use of inotropes or intra-aortic balloon pulsation. Additionally, segmental transmural myocardial infarction occurs in 1-5% of patients, and postoperative arrhythmias occur in approximately 30% of patients after CABG.[56]

Adverse neurologic outcomes are a major concern in cardiac surgery, with 3.1% for major (type I) events (eg, major neurologic deficits and coma) occurring in 3.1% of cases, and 3% for less-debilitating (type II) events (deterioration of intellectual function or memory). Both types of events result in a significant increase in mortality: 21% for type I events and 10% for type II.[57] Despite the increased mortality associated with type II events, the majority of survivors return to normal activity in the following 3-12 months.[58]

Postoperative renal failure is a significant cause of mortality after CABG. There is a 4% incidence of renal failure; 20% of these patients require dialysis, and the mortality is 50%.

 

Medication

Medication Summary

The aims of premedication are to minimize myocardial oxygen demands by reducing the heart rate and systemic arterial pressure and to improve myocardial blood flow with vasodilators.

The 2017 European Association for Cardio-Thoracic Surgery (EACTS) guidelines on perioperative medication in adult cardiac surgery[59] can be found at https://academic.oup.com/ejcts/article-lookup/doi/10.1093/ejcts/ezx314.

Anxiolytics, Benzodiazepines

Class Summary

Administration of temazepam immediately before CABG can decrease the risk of tachycardia and hypertension resulting from anxiety regarding the operation. In the operating room, intravenous (IV) administration of a small dose of midazolam before arterial line insertion can also reduce anxiety, tachycardia, and hypertension.

Temazepam (Restoril)

Temazepam depresses all levels of the CNS (eg, limbic and reticular formation), possibly by increasing the activity of GABA.

Midazolam

Midazolam is a short-acting benzodiazepine with a rapid onset of action.

Opioid Analgesics

Class Summary

Induction of anesthesia is accomplished by using high doses of opioid (usually fentanyl or remifentanil) to minimize the dose of propofol, etomidate, or thiopental and thereby maximize cardiovascular stability.

Fentanyl citrate (Duragesic, Abstral, Actiq, Fentora, Onsolis)

Fentanyl citrate is a synthetic opioid that has 75-200 times more potency and a much shorter half-life than morphine sulfate. It has fewer hypotensive effects than morphine and is safer in patients with hyperactive airway disease because of minimal or no associated histamine release. By itself, fentanyl citrate causes little cardiovascular compromise, although the addition of benzodiazepines or other sedatives may result in decreased cardiac output and blood pressure.

Fentanyl citrate is highly lipophilic and protein-bound. Prolonged exposure to it leads to accumulation of the drug in fat and delays the weaning process. Consider continuous infusion because of the medication's short half-life.

Remifentanil (Ultiva)

Remifentanil binds mu-opioid receptors at various sites within the CNS.

Anesthetic Agents

Class Summary

After standard monitoring equipment is attached and peripheral venous access achieved but before the arterial line is inserted, the midazolam dose is administered. Before placement of the arterial line, it should be ensured that a radial artery graft will not be used for CABG.

Propofol (Diprivan)

Propofol is a phenolic compound unrelated to other types of anticonvulsants. It has general anesthetic properties when administered intravenously. Propofol IV produces rapid hypnosis, usually within 40 seconds. The effects are reversed within 30 minutes, following the discontinuation of infusion. Propofol has also been shown to have anticonvulsant properties.

Etomidate (Amidate)

Amidate is a nonbarbiturate imidazole compound with sedative properties. It is short-acting and has a rapid onset of action; the duration of action is dose dependent (15-30 minutes). Its most useful feature as an induction agent is that it produces deep sedation while causing minimal cardiovascular effects.

The major application of amidate is induction for endotracheal intubation, particularly in patients with, or at risk for, hemodynamic compromise. Amidate has been shown to depress adrenal cortical function; however, this effect is not significant clinically during short-term administration. Since the drug is mixed in propylene glycol, continuous infusion is not recommended.

Thiopental

Thiopental is a short-acting barbiturate sedative-hypnotic with rapid onset and a duration of action of 5-20 minutes. Like methohexital, it is most commonly used as an induction agent for intubation. To use thiopental as a sedative, titrate in dosage increments of 25 mg (adjust to lower dose in children).

Isoflurane (Forane, Terrell)

Isoflurane is an inhalation anesthetic. It may have a myocardial protective effect and therefore is especially useful in off-pump surgery. Isofluranse potentiates the effects of muscle relaxants. Small doses of muscle relaxants can achieve complete paralysis when administered concomitantly with isoflurane.

Neuromuscular Blockers, Nondepolarizing

Class Summary

Nondepolarizing neuromuscular blockers are used in combination with a sedative as part of the rapid-sequence intubation process.

Pancuronium

Vecuronium may increase myocardial oxygen demand. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Vecuronium

Vecuronium may cause bradycardia in association with opioids. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Rocuronium (Zemuron)

Rocuronium may cause tachycardia. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Atracurium

Atracurium is not considered suitable for operations of long duration. It can cause hypotension secondary to histamine release. It is used to facilitate endotracheal intubation and provide neuromuscular relaxation during intubation and mechanical ventilation. It is given as an adjunct to a sedative or hypnotic agent.

Anticoagulants, Hematologic

Class Summary

Anticoagulants prevent recurrent or ongoing thromboembolic occlusion of the vertebrobasilar circulation.

Heparin

Heparin augments the activity of antithrombin III and prevents conversion of fibrinogen to fibrin. It does not actively lyse but is able to inhibit further thrombogenesis. It prevents the recurrence of a clot after spontaneous fibrinolysis.

 

Questions & Answers

Overview

Why is coronary artery bypass grafting (CABG) performed?

What are the American College of Cardiology (ACC) and the American Heart Association (AHA) class I indications for coronary artery bypass grafting (CABG)?

What are indications for coronary artery bypass grafting (CABG)?

What are contraindications for coronary artery bypass grafting (CABG)?

Which factors might predispose a patient to complications from coronary artery bypass grafting (CABG)?

What is included in preoperative evaluation for coronary artery bypass grafting (CABG)?

Which risk models are used to predict mortality from coronary artery bypass grafting (CABG)?

Which medications may be administered prior to coronary artery bypass grafting (CABG)?

What is the role of anesthesia in coronary artery bypass grafting (CABG)?

How are patients monitored during coronary artery bypass grafting (CABG)?

Where is the conduit harvested from for coronary artery bypass grafting (CABG)?

What are the surgical approaches used for coronary artery bypass grafting (CABG)?

What is the role coronary artery bypass grafting (CABG) in the treatment of coronary artery disease (CAD)?

How was coronary artery bypass grafting (CABG) developed as a treatment for coronary artery disease (CAD)?

What are the American College of Cardiology (ACC) and the American Heart Association (AHA) indications for coronary artery bypass grafting (CABG)?

Which indications for coronary artery bypass grafting (CABG) are associated with a survival benefit over medical therapy?

What are indications for coronary artery bypass grafting (CABG)?

Which factors increase the survival benefit of coronary artery bypass grafting (CABG)?

When is coronary artery bypass grafting (CABG) preferred over medical therapy?

Which factors increase the benefit of percutaneous coronary intervention (PCI) over coronary artery bypass grafting (CABG)?

When is coronary artery bypass grafting (CABG) recommended in patients with comorbidities?

What are contraindications for coronary artery bypass grafting (CABG)?

What are best practices in the performance of coronary artery bypass grafting (CABG)?

What are the technical recommendation for performance of coronary artery bypass grafting (CABG)?

What is the role of a multidisciplinary heart team in procedure planning for coronary artery bypass grafting (CABG)?

How are cerebrovascular complications of coronary artery bypass grafting (CABG) prevented?

What is the efficacy of coronary artery bypass grafting (CABG)?

What research is needed for future advances in coronary artery bypass grafting (CABG)?

Periprocedural Care

Which factors might predispose a patient to complications from coronary artery bypass grafting (CABG)?

What is included in the routine preoperative evaluation for coronary artery bypass grafting (CABG)?

What is the difference between "off pump" and "on pump" coronary artery bypass grafting (CABG)?

Which risk models are used to predict mortality from coronary artery bypass grafting (CABG)?

What is the role of premedication in coronary artery bypass grafting (CABG)?

How is anesthesia initially administered in coronary artery bypass grafting (CABG)?

Which agents are used for muscle relaxation in coronary artery bypass grafting (CABG)?

What procedures should be performed prior to coronary artery bypass grafting (CABG)?

How is anesthesia maintained during coronary artery bypass grafting (CABG)?

What is the patient positioning for coronary artery bypass grafting (CABG)?

How are patients monitored during coronary artery bypass grafting (CABG)?

What is included in surgery intensive care unit (SICU) management following coronary artery bypass grafting (CABG)?

Technique

What are harvesting sites for the conduit in coronary artery bypass grafting (CABG)?

How is a saphenous vein harvested for coronary artery bypass grafting (CABG)?

How are internal thoracic (mammary) arteries harvested for coronary artery bypass grafting (CABG)?

What is the usual incision used for coronary artery bypass grafting (CABG)?

What is the technique for coronary artery bypass grafting (CABG) with cardiopulmonary bypass and cardioplegic arrest?

What is the technique for cardiopulmonary bypass in coronary artery bypass grafting (CABG)?

What is the technique for placement of graft in coronary artery bypass grafting (CABG)?

What are benefits of off-pump coronary artery bypass grafting (CABG) compared to on-pump coronary artery bypass grafting (CABG)?

What is totally endoscopic coronary artery bypass grafting (CABG)?

What is the hybrid technique in coronary artery bypass grafting (CABG)?

What are complications of coronary artery bypass grafting (CABG)?

What are complications of coronary artery bypass grafting (CABG)?

Medications

What are role of premedication in coronary artery bypass grafting (CABG)?

Which medications in the drug class Anticoagulants, Hematologic are used in the treatment of Coronary Artery Bypass Grafting?

Which medications in the drug class Neuromuscular Blockers, Nondepolarizing are used in the treatment of Coronary Artery Bypass Grafting?

Which medications in the drug class Anesthetic Agents are used in the treatment of Coronary Artery Bypass Grafting?

Which medications in the drug class Opioid Analgesics are used in the treatment of Coronary Artery Bypass Grafting?

Which medications in the drug class Anxiolytics, Benzodiazepines are used in the treatment of Coronary Artery Bypass Grafting?