Coronary Artery Bypass Grafting

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[10] and the developed world,[11] and 16.5 million US adults (age ≥20 years) are affected by this disease annually.[10]  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.[10]

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.[12, 13] By the 1970s, CABG was found to increase survival rates in patients with multivessel disease and left main disease when compared with medical therapy.[14]

The relatively 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. It is recommended that Individuals under consideration for CABG undergo Society of Thoracic Surgeons (STS) risk stratification.[1]  Evaluation of CAD complexity in patients with multivessel CAD using tools such as the SYNTAX (Synergy Between PCI With TAXUS and Cardiac Surgery) score may be useful in guiding revacularization.[1]

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. Newer, 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.[15]

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.[16, 17, 18] Surprisingly, this procedure produced significant symptomatic relief in a few patients.[19]

In 1962, Sabiston, at Duke University, performed the first planned saphenous vein bypass operation for coronary revascularization.[20]  In 1964, Kolessov used the left internal thoracic (mammary) artery to bypass the left anterior descending artery without cardiopulmonary bypass,[21] and, in 1973, Carpentier introduced the use of radial artery grafts as conduits for CABG.[22, 23]

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.

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[2, 3] :

• 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 ^{[2, 3]} (Open Table in a new window)

 

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[24] :

• 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[24]

• 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[24]

• 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)[24]

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[24] :

• 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[24] :

• 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[24] :

• 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)

 

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)

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

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

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

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

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

  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)

  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)

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.

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.[25]  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.[26] 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%.[27]

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.[2] 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.[2] 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.[2] 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)

Procedure planning

The formation of a multidisciplinary heart team enables a balanced decision-making process (see Table 12 below).[28, 29] 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.[28]

Table 12. Multidisciplinary Decision Pathways, Patient Informed Consent, and Timing of Intervention ^[28] (Open Table in a new window)

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.[28] 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.[28]

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.

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.[30]

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.[31, 32]

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.[33] 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.[33]

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.[34] 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.[34]

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.[35]  However, more recent evidence from meta-analyses and the International Study of Comparative Health Effectiveness With Medical and Invasive Approaches (ISCHEMIA) trial found no advantage of CABG over medical therapy in stable ischemic heart disease.[1]

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.[36] However, only 20% of the patients (n = 150) underwent CABG. The best treatment strategy for this population remains to be determined.[36]

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.[37]  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.[37]

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.[38] 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.[39] 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.[39]

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.[40] 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).[41, 42]

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.[43] The American Heart Association recommends life-long antiplatelet therapy.[44]  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.[44]

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[4]

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.[5]

Routine preoperative investigations include the following[4] :

• 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.[45] 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.[46]

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.[47]

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,[5]  and the Society of Thoracic Surgeons (STS) Cardiac Surgery Risk Model,[6]  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.

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).[4, 7, 8] 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)[9]

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.[48, 49]

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.

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.[50]

• 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.

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

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.[51, 52, 53]  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.[54]

 

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).

 

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).

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.

 

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

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.

 

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.

 

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.[55]

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.[56]

A systematic review did not demonstrate any significant benefit of (OPCABG) compared with on-pump CABG (ONCABG) regarding mortality, stroke, or myocardial infarction.[57]

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.[58]

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.[59]

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.

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.[60]

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.[61] Despite the increased mortality associated with type II events, the majority of survivors return to normal activity in the following 3-12 months.[62]

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%.

Issuing Organizations and Classifications

Clinical guidelines on myocardial revascularization have been issued by the following organizations:

• American College of Cardiology (ACC)/American Heart Association (AHA)
• European Society of Cardiology (ESC)/European Association for Cardio-Thoracic Surgery (EACTS)
• Society of Thoracic Surgeons
• ACC/AHA/Society for Cardiovascular Angiography and Interventions (SCAI)

Recommendations have been classified in both ACC/AHA and ESC/EACTS guidelines according to the level of evidence supporting the usefulness and efficacy of the procedure[2, 63] :

• 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 may be harmful

Treatment Strategy Selection

The ACC/AHA,[2] ESC/EACTS,[63] and ACC/AHA/SCAI[1] guidelines give a class I recommendation to the use of a Heart Team approach in determining treatment strategy and selection of appropriate revascularization procedure (ie, percutaneous coronary intervention [PCI] or coronary artery bypass grafting [CABG]). The ACC/AHA guidelines define a Heart Team as “a multidisciplinary team composed of an interventional cardiologist and a cardiac surgeon who jointly 1) review the patient’s medical condition and coronary anatomy, 2) determine that PCI and/or CABG are technically feasible and reasonable, and, 3) discusses revascularization options with the patient before a treatment strategy is selected.”[2]

This approach is similar to the tumor board or “supreme court” approach to complex or high-risk cases, or where there are not enough data (gray areas). For instance, use in patients with unprotected left main or complex coronary artery disease (CAD) is recommended.[2] .

On the other hand, the 2014 ESC/EACTS guidelines revised its recommendation from previous guidelines to include the development and use of standardized, evidence-based, and interdisciplinary protocols for low-risk and common scenarios; however, in such cases, revascularization at the time of diagnostic angiography is recommended against in order to allow for full assessment of the optimal treatment strategy. Multidisciplinary systematic evaluation is still required for complex cases.[63]

The Society of Thoracic Surgeons (STS) and SYNTAX (Synergy between Percutaneous Coronary Intervention with TAXUS and Cardiac Surgery) scores are recommended by both ACC/AHA and ESC/EACTS guidelines for risk stratification to aid in clinical decision-making.[2, 63]

Emergency CABG

Both ACC/AHA and ESC/EACTS provide guidance on the use of CABG as an emergency procedure.[2, 63]

ACC/AHA guidelines provide a class I recommendation for CABG in the context of an ST-segment elevation myocardial infarction (STEMI) in cases where PCI has been impossible to perform or has failed and the patient has persistent pain and ischemia threatening a significant area of myocardium despite medical therapy.[2]  In the 2021 updated guidelines, this recommendation has been downgraded to class IIa.[1]

Other class I indications for emergency open heart surgery in the setting of STEMI include the following:

• Ventricular pseudoaneurysm
• Life-threatening ventricular arrhythmias
• Cardiogenic shock: In patients with STEMI and cardiogenic shock or hemodynamic instability, PCI or CABG (when PCI is not feasible) is indicated for improving survival, irrespective of the time delay from MI onset. ^[1]
• Mechanical complications such as ventricular septal defect, mitral valve insufficiency due to papillary muscle infarction or rupture, or free wall rupture: CABG is recommended at the time of surgery to improve survival. ^[1]

Emergency CABG is not recommended in the following cases[2] :

• Persistent angina but only a small area of ischemia AND hemodynamically stable
• No-reflow state (successful epicardial reperfusion with unsuccessful microvascular reperfusion)
• Ventricular tachycardia with scar and no evidence of ischemia

CABG after failed PCI

Recommendations for emergency CABG after failed PCI include the following[2] :

• Ongoing ischemia or threatened occlusion with myocardium at risk (class I)
• Hemodynamic compromise without impairment of coagulation and without a previous sternotomy (class I)
• Hemodynamic compromise with impairment of coagulation and without a previous sternotomy (class IIa)
• Hemodynamic compromise and previous sternotomy; emergency CABG may be considered (class IIb)
• Retrieval of a foreign body (eg, fractured guidewire or stent) in a crucial location (class IIa)

The updated 2021 ACC/AHA/SCAI guidelines note that emergency CABG is reasonable in individuals with non-ST elevation-acute coronary syndrome (NSTE-ACS) in whom PCI has failed and who have ongoing ischemia, hemodynamic compromise, or threatened arterial occlusion with substantial myocardium at risk, and who are appropriate candidates for CABG.[1]

Emergency CABG should not be performed after failed PCI in the absence of ischemia or threatened occlusion, or if revascularization is impossible or futile because of target anatomy or a no-reflow state.[1, 2]

Indications and Contraindications

For decisions and recommendations on revascularization, the ACC/AHA guidelines, released in 2011, define significant stenosis as ≥70% diameter narrowing (≥50% for left main CAD). Physiological criteria, such as fractional flow reserve ≤0.80, may also be considered significant. In addition, some recommendations use SYNTAX scores as surrogates for the extent and complexity of CAD.[2]

CABG may be performed to improve symptoms and/or improve survival, with the latter generally given greater weight when selecting a procedure. The guidelines note that in discussions of options, the patient should clearly understand the goal of the procedure (symptom relief, improved survival, or both) before a decision is made.[2]

CABG for symptom improvement

Recommendations for CABG for symptom improvement are as follows[2, 63] :

• Significant stenosis and unacceptable angina despite medical therapy (class I recommendation for both ACC/AHA and ESC/EACTS)
• Significant stenosis and unacceptable angina in patients with medication contraindications or adverse effects, or patient preference (ACC/AHA class IIa)
• In a good candidate, CABG may be considered over PCI for complex three-vessel CAD (eg, STYNTAX score >22) with or without involvement of the proximal LAD artery (ACC/AHA class IIa but ESC/EACTS class I)
• Transmyocardial laser revascularization (TLR) as an adjunct to CABG may be considered in patients with viable ischemic myocardium that is perfused by coronary arteries that are not amenable to grafting (ACC/AHA class IIb)

CABG for survival improvement

ACC/AHA and ESC/EACTS recommendations for CABG to improve survival are compared in Table 13, below.[2, 63]

Table 13. Indications for Coronary Artery Bypass Grafting (Open Table in a new window)

In the updated ACC/AHAI/SCAI guidelines, elective CABG is reasonable after successful primary PCI in selected patients with STEMI with complex multivessel noninfarct artery disease (class IIa).[1]  For those who require revascularization for significant left main CAD with high-complexity CAD, CABG is recommended over PCI for survival improvement (class I). It is reasonable to choose CABG over PCI to confer survival advantage in patients who require revascularization for multivessel CAD with complex or diffuse CAD (eg, SYNTAX score >33).[1]

For recommendations on management of stable ischemic heart disease, see Table 14, below.

 Table 14. Updated ACC/AHA/SCAI Recommendations for Revascularization for Survival Improvement in Stable Ischemic Heart Disease Versus Medical Therapy ^[1] (Open Table in a new window)

Class IIa recommendations state revascularization is reasonable to reduce the risk of cardiovascular events (eg, spontaneous MI, unplanned urgent revascularizations, cardiac death) in those with stable ischemic heart disease and multivessel CAD that is appropriate for either CABG or PCI.[1]

Neither CABG nor PCI should be performed in those with angina but no anatomic or physiologic criteria for revascularization.[1]

Previous CABG

It is reasonable to choose CABG over PCI in patients with previous CABG in the following settings[1] :

• Refractory angina on medical therapy that is attributable to left anterior descending (LAD) artery disease when an internal mammary artery (IMA) can be used as a conduit to the LAD (class IIa)
• Complex CAD when an IMA can be used as a conduit to the LAD (class IIb)

It is reasonable to select PCI over CABG in those with a previous CABG and a patent left IMA (LIMA) to the LAD artery who need revascularization, providing PCI is feasible (class IIa).[1]

CABG is reasonable over PCI in patients with multivessel CAD that is amenable to treatment with either PCI or CABG who are unable to access, tolerate, or adhere to dual antiplatelet therapy.[1]

Comorbidities/Higher-Risk Cohorts

Diabetes mellitus

The ACC/AHA recommends CABG over PCI for improved survival in patients with comorbid diabetes mellitus (DM) and multivessel CAD, particularly with use of the LIMA; the recommendation was upgraded from class IIa in the 2011 guidelines to class I in the 2014 guidelines and remains class I in the 2021 updated guidelines.[ref76} However, the use of bilateral internal mammary arteries is associated with increased risk of infection and should be considered only when the benefit outweighs the increased risk (class IIb).[2]  In diabetic persons with left main stenosis and low- or intermediate-complexity CAD in the rest of their coronary anatomy, PCI may be considered an alternative to CABG to reduce major adverse cardiovascular outcomes.[1]

In a 2014 update of the guidelines for patients with stable ischemic heart disease (IHD), the American College of Cardiology (ACC)/American Heart Association (AHA)/American Association for Thoracic Surgery (AATS)/Preventive Cardiovascular Nurses Association (PCNA)/Society for Cardiovascular Angiography and Intervention (SCAI)/Society of Thoracic Surgeons (STS) provided the following recommendations for patients with stable IHD and DM[64] :

• Patients should receive medical therapy
• Revascularization should be considered for patients with symptoms that remain inadequately controlled despite medical therapy
• A Heart Team approach is beneficial in the evaluation of CABG versus PCI; mortality risk appears to be lower with CABG than with PCI in most patients with DM and complex multivessel disease, but exceptions may be identified

The ESC/EACTS guidelines recommend CABG as the revascularization modality of choice for improved survival in patients with DM and multivessel or complex (SYNTAX Score >22) CAD. However, PCI can be considered as a treatment alternative in diabetic patients with multivessel disease and a low SYNTAX score (≤22).[63]

Kidney disease

In the setting of end-stage renal disease, the ACC/AHA consider CABG as reasonable (class IIb recommendations) for the following indications[2] :

• To improve survival for patients with left main coronary artery stenosis ≥50%
• To improve survival and relieve symptoms resistant to medical therapy in patients with ≥70% stenosis in three major vessels or in the proximal LAD artery plus one other major vessel

CABG should not be performed in patients with end-stage renal disease whose life expectancy is limited because of noncardiac conditions.[2]

The ESC/EACTS guidelines prefer CABG over PCI for patients with multivessel CAD and chronic kidney disease (CKD) when surgical risk is acceptable and life expectancy is longer than 1 year; PCI is preferred for those patients with high surgical risk and/or life expectancy of less than 1 year but may be challenging in those with heavily calcified coronaries. Considerations include delaying CABG until the effects of angiography on renal function have subsided.[63]

Valvular disease

The ACC/AHA recommendations for patients with valvular disease are as follows[2] :

• Aortic valve replacement for patients with moderate or worse aortic stenosis undergoing CABG (class I)
• Patients with ischemic mitral valve regurgitation that is not likely to be resolved with revascularization should have concurrent mitral valve repair or replacement while undergoing CABG (class I recommendation for severe regurgitation, class IIa for moderate regurgitation, class IIb for mild regurgitation)
• In patients undergoing concurrent valvular surgery, intraoperative transesophageal echocardiography should be performed (class I)

The ESC/EATS recommendations include the following[63] :

• Perform CABG in patients with stenosis >70% in a major vessel and an aortic/mitral valve surgery indication (class I)
• Consider CABG in patients with stenosis 50-70% in a major vessel and an aortic/mitral valve surgery indication (class IIa)
• Perform mitral valve surgery in patients with severe mitral regurgitation and LVEF >30% who are undergoing CABG (class I)
• Consider mitral valve surgery in patients with moderate mitral regurgitation who are undergoing CABG (class IIa)
• Consider repair of moderate-to-severe mitral regurgitation in patients undergoing CABG who have LVEF≤35% (class IIa)
• Consider aortic valve surgery in patients with moderate aortic stenosis who are undergoing CABG (class IIa)

Carotid/peripheral artery disease

The ACC/AHA guidelines provide the following recommendations for patients with comorbid carotid artery disease[2] :

• Patients with significant carotid artery disease require a multidisciplinary team (cardiologist, cardiac surgeon, vascular surgeon, and neurologist) approach (class I)
• Patients with high-risk features (ie, age >65 years, left main artery stenosis, PAD, hypertension, smoking, diabetes mellitus, history of stroke or transient ischemic attack [TIA]) should undergo carotid artery duplex screening (class IIa)
• Carotid revascularization may be considered in CABG patients with previous TIA or stroke and significant (50-99%) carotid artery stenosis
• Timing of carotid intervention (synchronous or staged) should be based on relative magnitude of cerebral and myocardial dysfunction or jeopardy (class IIa)
• Carotid revascularization may be considered in patients with no history of TIA or stroke but severe bilateral (70-90%) carotid stenosis or unilateral severe carotid stenosis with contralateral occlusion (class IIb)

The ESC/EACTS guidelines for carotid artery revascularization in CABG patients include the following[63] :

• Carotid endarterectomy (CEA) or carotid artery stenting (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)
• Indications for carotid revascularization should be individualized after discussion by a multidisciplinary team, including a neurologist (class I)
• Timing of procedures (synchronous versus staged) should be dictated by local expertise and clinical presentation, with the most symptomatic territory targeted first (class IIa)
• In patients with a history of TIA/stroke, carotid revascularization is recommended for 70-99% carotid stenosis in both men and women (class I) and may be considered for 50-69% carotid stenosis, depending on patient-specific factors and clinical presentation (class IIb)
• In patients with no history of TIA/stroke, carotid revascularization may be considered in men with bilateral 70-99% carotid stenosis, 70-99% carotid stenosis and contralateral occlusion, or 70-99% carotid stenosis and ipsilateral previous silent cerebral infarction (class IIb)
• Choice of carotid revascularization modality (CEA vs CAS) in patients undergoing CABG should be based on patient comorbidities, supra-aortic vessel anatomy, urgency of CABG, and local expertise (class IIa)
• Acetylsalicylic acid (ASA) immediately before and after carotid revascularization (class I)
• Dual antiplatelet therapy with ASA and clopidogrel for at least 1 month in patients undergoing CAS (class I)

The ESC/EACTS advise that CAS should be considered in patients with any of the following (class IIa):

• Post-radiation or post-surgical stenosis
• Obesity
• Hostile neck
• Tracheostomy
• Palsy
• Stenosis at different carotid levels or upper internal carotid artery stenosis
• Severe comorbidities contraindicating CEA

CABG Conduit Selection

The ACC/AHA guidelines make the following recommendations for bypass graft conduit selection[2] :

• Left internal mammary artery (LIMA) to bypass left anterior descending (LAD) artery (class I)
• Right internal mammary artery when LIMA is unavailable or unsuitable as a bypass conduit (class IIa)
• When anatomically and clinically suitable, use of a second internal mammary artery to graft the left circumflex or right coronary artery is reasonable to improve survival and decrease likelihood of reintervention (class IIa). This is weighed against the slightly increased risk of deep sternal wound infections in diabetics or the morbidly obese.
• In patients ≤60 years old with few or no comorbidities, complete arterial revascularization may be considered (class IIb)
• Arterial grafting of the right coronary artery when ≥90% stenosis (class IIb)
• Radial artery graft when grafting left-sided arteries with severe stenosis (>70%) and right-sided arteries with critical stenosis (≥90%) that perfuse LV myocardium (class IIb)

Guidelines on conduit selection from by the Society of Thoracic Surgeons include the following recommendations:

• Internal thoracic arteries (ITAs) should be used to bypass the LAD artery when bypass of the LAD is indicated
• As an adjunct to left internal thoracic artery (LITA), a second arterial graft (right ITA or radial artery) should be considered in appropriate patients
• Use of bilateral ITAs (BITAs) should be considered in patients who do not have an excessive risk of sternal complications
• To reduce the risk of sternal infection with BITA, skeletonized grafts should be considered, smoking cessation is recommended, glycemic control should be considered, and enhanced sternal stabilization may be considered
• As an adjunct to LITA to LAD (or in patients with inadequate LITA grafts), use of a radial artery graft is reasonable when grafting coronary targets with severe stenoses
• When radial artery grafts are used, it is reasonable to use pharmacologic agents to reduce acute intraoperative and perioperative spasm
• The right gastroepiploic artery may be considered in patients with poor conduit options or as an adjunct to more complete arterial revascularization
• Use of arterial grafts (specific targets, number, and type) should be a part of the discussion of the heart team in determining the optimal approach for each patient

Antiplatelet Therapy

Recommendations for the management of antiplatelet therapy in patients undergoing CABG have been provided by the following organizations:

• American College of Cardiology (ACC)/American Heart Association (AHA) – For patients undergoing CABG ^[2] or those with unstable angina/non–ST-elevation myocardial infarction (NSTEMI) ^[65] or non–ST-elevation acute coronary syndromes ^[66]
• European Society of Cardiology (ESC) – For patients undergoing CABG ^[67]

For preoperative management of antiplatelet therapy, see Table 15, below.[2, 65, 66, 67, 68]

Table 15. Preoperative management of antiplatelet therapy in patients undergoing CABG (Open Table in a new window)

For postoperative management of antiplatelet therapy, see Table 16, below.[2, 65, 66, 67, 68]

Table 16. Postoperative management of antiplatelet therapy in patients undergoing CABG (Open Table in a new window)

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.

See the 2017 European Association for Cardio-Thoracic Surgery (EACTS) guidelines on perioperative medication in adult cardiac surgery[69] for more information.

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.

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.

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.

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.

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.