Coronary Artery Bypass Grafting

Updated: Oct 30, 2017
  • Author: Rohit Shahani, MD, MS, MCh; Chief Editor: Karlheinz Peter, MD, PhD  more...
  • Print
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
Next:

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.

Previous
Next:

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.
Previous
Next:

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.

Previous
Next:

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.

Previous
Next:

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]

Previous
Next:

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]

Previous