34. Stable Ischemic Heart Disease-Clinical Scenarios

Charles M. Wojnarski, MD, MS, and Peter K. Smith, MD

Adapted from 1st edition chapter, “Stable Angina” written by Mark Kearns, MD, and Richard C. Cook, MD

Key Concepts

  • Preoperative evaluation
  • Indications for coronary artery bypass graft (CABG) surgery vs. percutaneous coronary intervention (PCI)
  • Operative conduct
  • General topics and evidence-base
  • Conduit selection
  • Patient scenarios and intra-operative complications


Patient Scenario: Chief Complaint

“A 78 y.o. male with new onset exertional chest pain presents to your clinic. His primary care physician ordered an exercise stress test which was grossly positive. He was then referred for left heart catheterization (LHC) which revealed 3-vessel coronary artery disease. The patient was told he needs bypass surgery and is here to for pre-operative evaluation.”


General Considerations:

Patients with stable ischemic heart disease often present with exertional angina. At rest, coronary perfusion may be adequate; however, in the face of increased oxygen demand during periods of increased cardiac output, a supply-demand mismatch occurs as coronary vasodilatory mechanisms cannot overcome fixed, flow-limiting stenoses. Chest pain at rest, exertional angina not relieved by rest and new onset chest pain represent unstable angina, which should not be evaluated in the outpatient setting.

Guideline-directed medical therapy (GDMT) including lifestyle modification, statin therapy to achieve a low-density lipoprotein (LDL) level of 70-100 mg/dL, beta-blockade, aspirin and ACE inhibition in patients with left ventricular dysfunction, diabetes mellitus or chronic kidney disease should be initiated in all patients with stable ischemic heart disease. If non-invasive tests suggest high-risk coronary lesion(s), coronary interrogation with formal angiography or gated CT should be performed. A “Heart Team” approach to revascularization is recommended in patients with diabetes mellitus or complex multivessel coronary artery disease.

History and Physical

Patient comorbidities can have an important impact on choice of intervention and surgical planning. A history of diabetes mellitus, severe peripheral arterial disease, and symptomatic cerebrovascular disease should always be elicited. Previous chest, upper abdomen or extremity surgery or radiation may impact availability of arterial or venous conduit. Every effort should be made to obtain specific anatomic details of previous percutaneous interventions (PCI) and ascertainment of antiplatelet medication use is essential for the perioperative management of antiplatelet therapy.

The physical exam should be focused on findings that may impact operative plan or perioperative risk-stratification. A baseline neurologic exam should be documented. Cardiopulmonary examination should be performed to identify signs of heart failure, valvular abnormalities or COPD. Modified Allen’s test with pulse oximetry should be performed for screening if radial artery conduit is to be used despite its high false-positive rate. Equivocal results should be further investigated with arterial duplex ultrasounography. Evidence of previous lower extremity vascular surgery or venous insufficiency should be further investigated with vein mapping study to determine saphenous vein suitability.

Pre-operative Testing

Laboratory investigations: Pre-surgical evaluation should include hematologic, biochemical and coagulation laboratory studies. Hemoglobin A1c (HbA1c) level should be obtained prior to surgery in patients with diabetes.

EKG: It is critical to establish a baseline electrocardiogram which can be referenced in the post-operative period. Rate, rhythm, axis-deviation or suggestion of LV hypertrophy should be noted.

CXR: Pre-operative radiographic chest examination should be assessed with attention to cardiac silhouette, presence of any pulmonary parenchymal disease and note should be made of any ascending aortic/aortic arch calcification. Occasionally a widened mediastinum may suggest an ascending aortic aneurysm. Note should be made of any pre-existing pleural effusions.

LHC: Coronary artery bypass grafting surgery cannot be done without proper angiographic assessment of the coronary anatomy, degree and location of stenoses, and general suitability for bypass grafting – all depicted by selective coronary angiography. Aortography, if performed, defines ascending aortic and root size, can be used to screen for aortic calcification, and may suggest the presence of aortic regurgitation. Careful observation of the aorta, root and valve plane during cinefluoroscopy may reveal calcification and affect decision making. Left ventriculography can inform one of LV function, LV chamber dilation and may be able to show aortic stenosis or mitral regurgitation. Anatomically, left main (LM) lesions ≥ 50% or non-LM coronary artery lesions ≥ 70% are hemodynamically significant.

Fractional flow reserve (FFR £ 0.80) is a physiologic determinant of hemodynamic significance of the cumulative effect of proximal coronary stenoses. FFR can be a useful adjunct  to guide revascularization in angiographically intermediate coronary stenoses in patients with stable angina (Class 1) based on evidence from three large RCTs: DEFER, FAME, and FAME 2.It should be noted that the use of FFR to guide bypass grafting decision making is inferred from these PCI trials, and has never been studied directly. iFR (instantaneous wave-free ratio) is an emerging physiologic measurement which can also be used to determine hemodynamic significance of a lesion (iFR £ 0.89).

The SYNTAX score is the sum of the points assigned to each individual lesion identified in the coronary tree (divided into 16 segments) with >50% diameter narrowing in vessels >1.5mm diameter. A score ≥ 23 is considered is considered intermediate complexity and ≥ 33 represents high complexity disease. The Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) trial, assessed the optimal revascularization strategy for patients with previously untreated three-vessel or left main coronary artery disease. The trial showed the benefit of CABG over PCI regarding major adverse cardiac and cerebrovascular event at 5-years in patients with multivessel and left main coronary artery disease (26.9% vs. 37.3%, p<0.0001). At 10-year follow-up, the three-vessel disease subset had the patients whom underwent CABG had lower all-cause mortality (21.9% vs. 29.2%, p=0.007), especially among patients with a high SYNTAX score.

Gated cardiac computed tomography has emerged as a non-invasive option for imaging the coronary arteries.  In certain patients, this can replace the need for LHC.

Echocardiogram: All patients undergoing CABG should have a pre-operative ECHO to determine LV and RV function and identify any valvular abnormalities that might be concomitantly addressed. Regional wall motion abnormalities may help determine the physiologic significance of borderline lesions.

Myocardial viability studies: Can be considered in patients with left ventricular ejection fraction (LVEF) ≤ 35% or those with ventricular dysfunction out of proportion to severity of coronary artery disease. However, a recent secondary analysis of the STITCH trial including 601 patients that had pre-operative viability studies showed that myocardial viability was not related to long-term benefit from CABG in patients with low LVEF. Viability was associated with improvement in EF post-operatively, but this did not translate into a survival benefit (test for interaction, p=.34). Therefore, the absence of myocardial viability does not obviate the survival benefit from CABG over medical therapy in patients with low LVEF.

Additional investigations: Generally, other studies are indicated by any major comorbidities of the patient and aid in risk-stratification. Any abnormality of the pre-operative CXR which may impact surgical plan should be followed up with a cross-sectional CT of the chest. This will help assess degree of aortic calcification as porcelain aorta will impact one’s ability to place an aortic cross-clamp and may suggest an aortic no-touch, off-pump technique.

Carotid artery duplex scanning is reasonable in selected patients who are considered to have high-risk features (i.e., age >65 years, left main coronary stenosis, peripheral artery disease, history of cerebrovascular disease [transient ischemic attack, stroke, etc.], hypertension, smoking, and diabetes mellitus). Pulmonary function tests (PFTs) can be considered for patients with a history of pulmonary disease but are unlikely to impact operative management or candidacy. Most additional studies provide information for risk stratification and predicting major morbidity and mortality. The STS risk calculator should be used to counsel patients on individualized risks of operation. Predicted outcomes provided by the calculator include mortality, renal failure, permanent stroke, prolonged ventilation, sternal wound infection, reoperation, morbidity or mortality, short, long length of stay.

Patient Scenario – Additional Information

“On further questioning, the patient has diabetes mellitus type II (HbA1c 8.5%, on insulin), hypertension, hyperlipidemia, and is a former smoker. He has a 6-month history of exertional dyspnea and angina. You review his LHC which shows a chronic total occlusion (CTO) of his right coronary artery (RCA), a focal 80% proximal left anterior descending (LAD) artery stenosis and a 75% stenosis of a large first obtuse marginal artery (OM1). Echocardiogram reveals an LVEF of 45%, antero-lateral wall hypokinesis, but no valvular abnormalities. His SYNTAX score is 26 and STS predicted risk of mortality is 1.5%.

Indications for coronary artery bypass graft surgery:

The 2011 ACC/AHC Guideline on Coronary Artery Bypass Graft Surgery and 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS Guideline for the Diagnosis and Management of Patients with Stable Ischemic Heart Disease with 2014 Focused Update are the two main documents which outline the indications for CABG as they relate to PCI:

Indications for CABG that are associated with a survival benefit over medical therapy with or without PCI:

  • Left main coronary artery disease (≥50% stenosis) and high complexity for PCI (SYNTAX score ≥33). (Class I)
  • Three-vessel coronary artery disease (≥70% stenosis) and intermediate or high complexity for PCI (SYNTAX score ≥23). (Class I)
  • Two-vessel coronary artery disease (≥70% stenosis) involving the LAD artery and intermediate or high complexity for PCI (SYNTAX score ≥23). (Class I)
  • Patients with diabetes mellitus and multivessel CAD for which revascularization is likely to improve survival (3-vessel CAD or complex 2-vessel CAD involving the proximal LAD), particularly if a LIMA graft can be anastomosed to the LAD artery, provided the patient is a good candidate for surgery. (Class I)

Indications for CABG when PCI is noninferior to CABG and when PCI or CABG is preferred over medical therapy

  • Left main coronary artery disease (≥50% stenosis) and low-to-intermediate complexity for PCI (SYNTAX score ≤32). (Class IIa)
  • Three-vessel coronary artery disease (≥70% stenosis) and low complexity for PCI (SYNTAX score ≤22). (Class IIa)
  • Two-vessel coronary artery disease (≥70% stenosis) involving the LAD artery and low complexity for PCI (SYNTAX score ≤22). (Class IIa)

Other indications for CABG:

  • Clinically significant coronary artery disease (≥70% stenosis) in ≥1 vessel and refractory angina despite medical therapy and PCI. (Class I)
  • Clinically significant coronary artery disease (≥70% stenosis) in ≥1 vessel in survivors of sudden cardiac arrest presumed to be related to ischemic ventricular arrhythmia. (Class I)
  • Clinically significant coronary artery disease (≥50% stenosis) in ≥1 vessel in patients undergoing cardiac surgery for other indications. (e.g., valve replacement or aortic surgery) (Class I)

The 2016 Society of Thoracic Surgeons (STS) Clinical Practice Guidelines on Arterial Conduits for Coronary Artery Bypass Grafting provides additional procedural guidance:

  • Internal mammary arteries (IMA) should be used to bypass the left anterior descending (LAD) artery when bypass of the LAD is indicated. (Class I)
  • As an adjunct to left internal mammary artery (LIMA), a second arterial graft (RIMA or radial artery [RA]) should be considered in appropriate patients. (Class IIa)
  • Use of bilateral IMAs (BIMA) should be considered in patients who do not have an excessive risk of sternal complications. (Class IIa)
  • To reduce the risk of sternal infection with BIMA, skeletonized grafts should be considered. (Class IIa)
  • As an adjunct to LIMA to LAD (or in patients with inadequate LIMA grafts), use of a RA graft is reasonable when grafting coronary targets with severe stenoses. (Class IIa)
  • The right gastroepiploic artery may be considered in patients with poor conduit options or as an adjunct to more complete arterial revascularization. (Class IIb).
  • 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. (Class I)

It is worth mentioning that there is much controversy about the clinical trials that have led to the conclusions that PCI may be preferable or equivalent to CABG in patients with LM disease and low SYNTAX. 

Patient Scenario – Treatment Plan

The patient in this scenario has a class I indication for coronary artery bypass graft surgery given his symptomatic, complex coronary artery disease. The presence of three-vessel coronary artery disease in this patient with diabetes and depressed LVEF further strengthens the case for CABG over multivessel PCI for survival benefit. A multidisciplinary heart team met to discuss the patient and determined that at age 78, choice of conduits would include a LIMA to the LAD and saphenous vein grafts to the remaining targets.

Operative Conduct: (Sample Operative Note)

Procedures:

1. Median sternotomy

2. Coronary artery bypass grafting x3: LIMA-LAD, SVG-OM1, SVG-PDA

3. Endoscopic saphenous vein harvest, right leg

4. Transesophageal echocardiography

Drains and Wires: 2 mediastinal 28fr chest tubes, 1 left pleural 28fr chest tube; atrial and ventricular epicardial pacing wires

Cross-clamp time: 62 min

CBP time: 84 min　

Procedure in detail:  The risks, benefits, complications, treatment options, and expected outcomes were discussed with the patient. Informed consent was obtained, and time out was performed.  Hemodynamic monitoring lines and Foley catheter were placed. Following oral endotracheal tube placement, general anesthesia was induced. The patient’s skin was prepped with chlorhexidine-alcohol based solution from chin to toes. The chest, abdomen, groins and legs were draped in standard fashion. Transesophageal echocardiography demonstrated normal LV-RV function and no aortic valve insufficiency or other valvular abnormalities. Median sternotomy was performed. The left pleural space was opened. The left internal mammary artery was taken down as a pedicled graft using a combination of clips and cautery. Intravenous heparin was given at the appropriate dose to obtain anticoagulation sufficient for cardiopulmonary bypass (ACT ³480). The LIMA was then transected distally, and flow was demonstrated to be excellent. The mammary bed was hemostatic. A left pleural chest tube was placed.  The pericardium was then opened, and the pericardial cradle created. Concentric purse strings were placed, and the aorta was cannulated with an 18 Fr straight cannula. After adequate de-airing, this cannula was connected to the CPB circuit. A purse string was placed around the right atrial appendage and it was cannulated with a dual-stage venous cannula. Cardiopulmonary bypass was then initiated, and ventilation held. Perfusion temperature was allowed to drift to 32°C. A window was created in the left pericardium with care to preserve the phrenic nerve and the LIMA was fashioned to the appropriate length.

The distal targets on the posterior descending artery (PDA), first obtuse marginal artery (OM1) and left anterior descending artery (LAD) were then evaluated and marked. The IVC was encircled and a heart basket was then placed into the appropriate position. An antegrade vent/cardioplegia cannula was then placed in the ascending aorta. The aortic cross clamp was then applied, and the heart was arrested with 1200 cc of antegrade Del Nido cardioplegia. Topical iced-saline slush was employed as an adjunct for myocardial preservation.  The distal anastomosis to the PDA was completed first. After exposing the PDA, the artery was opened and SVG was anastomosed to the coronary using 7-0 polypropylene suture in a standard running fashion. The anastomosis was checked for hemostasis which was excellent. The graft was sized and divided at appropriate length. The distal anastomosis to the OM1 was completed next. After exposing the OM1, the artery was opened and SVG was anastomosed to the coronary using in the standard running fashion. The anastomosis was checked for hemostasis which was excellent. The graft was sized and divided at appropriate length. Next the anterior surface of the heart was exposed. LIMA to LAD anastomosis was completed in the standard running fashion. The anastomosis was checked for hemostasis which was excellent.

Antegrade cardioplegia vent was removed and two punches were made in aorta anteriorly. Proximal SVG anastomoses were performed with 6-0 polypropylene suture in running fashion. The aorta was de-aired and the cross clamp removed. Examination of all surgical sites revealed adequate hemostasis. Atrial and ventricular epicardial pacing wires were then placed. The patient was ventilated and successfully weaned off CPB. After a test dose of protamine, the patient was decannulated. Heparin was then reversed with protamine. Again, all surgical sites were evaluated for hemostasis which was excellent. Post-bypass TEE revealed preserved RV/LV function and no new wall motion abnormalities. Two mediastinal drains were placed. The sternum was closed using stainless steel wires and the incision closed in a standard fashion. A dry, sterile dressing was placed. At the end of the operation, all sponge, instruments, and needle counts were correct. The patient tolerated the procedure without complication and was transported to the intensive care unit in stable condition in normal sinus rhythm with epicardial pacer set to VVI backup rate of 50.

General Topics and Evidence-Base:

On-pump CABG (ONCAB) vs. Off-pump CABG (OPCAB)

In the United States, approximately 85-90% of coronary artery bypass graft surgeries are performed with the use of cardiopulmonary bypass. In the year 2016, the STS National Adult Cardiac Database showed 13% utilization of off-pump CABG. Off-pump and on-pump CABG have similar short‐term outcomes. In the long term, OPCAB may have inferior outcomes compared to ONCAB, likely due to higher rates of incomplete revascularization. A 2018 systematic review of 30-years of literature comparing OPCAB and ONCAB by Gaudino, et al. summarizes the evidence best:

  • “In the largest randomized comparisons (CORONARY [CABG Off or On Pump Revascularization] and ROOBY [Randomized On/Off Bypass] trials), there were no differences in the primary study end point at 30 days. In CORONARY, the primary composite outcome of death, nonfatal stroke, or nonfatal myocardial infarction (MI) was similar between OPCAB and ONCAB (9.8% versus 10.3%, p=0.59). In ROOBY, the primary composite outcome of 30‐day death or major complications was similar between the 2 arms (7.0% versus 5.6%, p=0.19).”
  • “At 5 years, there was no difference in the primary outcome in the CORONARY trial. In the ROOBY trial, however, 5‐year survival was significantly worse in the off‐pump group (15.2% versus 11.9%; p=0.02). Event‐free survival was also significantly decreased in the off‐pump group (31.0% versus 27.1%; p=0.05), along with MI and the need for repeat revascularization.”
  • “The available evidence suggests that OPCAB can be associated with better outcomes in high‐risk patents. Elderly patients, patients with low EF, those with high neurological risk, women, and patients with end‐organ failure may benefit from off‐pump surgery, although the extent of this benefit remains unclear at present.”

Bilateral Internal Mammary Artery (BIMA) vs. Single Internal Mammary Artery Revascularization:

The largest randomized-controlled trial comparing bilateral to single IMA revascularization is the ART trial (Arterial Revascularization Trial). 3,102 patients were randomly assigned to undergo either bilateral IMA or single IMA. In the intention-to-treat analysis at 10 years, was no difference between groups regarding all-cause mortality (hazard ratio [HR], 0.96; 95% confidence interval [CI], 0.82 to 1.12; p=0.62). Regarding the composite outcome of death, myocardial infarction, or stroke, there were 385 patients (24.9%) with an event in the bilateral-graft group and 425 patients (27.3%) with an event in the single-graft group (HR, 0.90; 95% CI, 0.79 to 1.03). A major criticism of the trial was high crossover: in the bilateral-graft group, 13.9% of the patients received only a single internal mammary artery graft, and in the single-graft group, 21.8% of the patients also received a radial artery graft.

The main disadvantage of BIMA grafting is a 2-3-fold increased risk of sternal wound complications. Known risks of sternal infection and malunion include nonelective procedure, age, uncontrolled DM (HbA1c >7%), obesity (BMI >40 kg/m2), pre-operative hospital stays of >3 days, female sex, COPD, active smoking, immunosuppression regimen, and radiation mediastinal injury.

CABG in patients with diabetes mellitus:

The FREEDOM trial was a prospective, multicenter, randomized clinical trial that compared CABG to PCI with drug eluting stents in 1900 patients at 140 centers with diabetes and multivessel CAD. The primary outcome analyzed was a composite of death from any cause, nonfatal myocardial infarction, or nonfatal stroke. CABG had a lower 5-year rate of primary outcome (18.7%, n=147) as compared to PCI (26.6%, n=352; p=.005). The benefit of CABG over PCI persisted across all categories of SYNTAX score.

CABG in patients with low ejection fraction:

The Surgical Treatment for Ischemic Heart Failure (STICH) trial compared CABG with medical therapy in a group of patients with multivessel coronary artery disease and LVEF ≤ 35%. In the initial STITCH trial, CABG did not significantly reduce all-cause mortality (the primary outcome) as compared with medical therapy at 56 months (36% vs. 41%, p=0.12). However, recently published long-term follow-up of the STICH population (STITCHES) showed that after almost 10 years of follow-up, patients assigned to CABG, as compared with patients assigned to medical therapy, had lower rates of death from any cause (58.9% vs. 66.1%, p=0.02), of death from cardiovascular causes (40.5% vs. 49.3%, p=0.006), and of death from any cause or hospitalization for cardiovascular causes (76.6% vs. 87.0%, p<0.001).

Intra-operative transit-time flow measurement (TTFM) of coronary bypass grafts:

A recent systematic review and meta-analysis of 35 relatively small prospective and retrospective studies showed that TTFM has a low sensitivity (0.25-0.46), but had excellent specificity for identifying abnormal graft flow (0.94-0.98).17 Although not standardized, generally accepted cutoff values indicating abnormal graft flow are mean graft flow (MGF) <15ml/min for arterial and <20ml/min for venous grafts, pulsatility index (PI) ³ 5 for both arterial and venous grafts, and diastolic filling percent <50% for both arterial and venous grafts. These parameters, in addition to surgeon judgement and clinical scenario may indicate need for intra-operative graft revision. Most commonly, addressing twisting or kinking of the graft and revision of distal anastomosis leads to resolution of abnormal flow patterns.

Myocardial temperature monitoring:

No large-scale retrospective or prospective randomized data exists on this topic and its use varies by institution and surgeon. If used, the probe is placed directly to the right of the LAD into the septum. Adequate cold cardioplegia supply to the myocardium is suggested by a septal temperature of 10-15°C. However, this tool should be used as an adjunct to other indicators of adequacy of delivery of cardioplegia including aortic root pressure, time to arrest and direct visualization of coronary content color change. In cases where proximal disease is severe and adequacy of antegrade delivery is in question, retrograde cardioplegia delivery through the coronary sinus can be considered. Myocardial protection as a topic is beyond the scope of this review but is a critical aspect of any coronary artery bypass procedure.

Perioperative anti-platelet therapy:

Aspirin (100 to 325 mg daily) should be administered to CABG patients preoperatively (Class I; Level of Evidence [LOE]: B). If aspirin was not initiated preoperatively, it should be initiated within 6 hours postoperatively and then continued indefinitely to reduce the occurrence of saphenous vein graft closure and adverse cardiovascular events (Class I; LOE: A).

For elective CABG, clopidogrel (Plavix) and ticagrelor (Brilinta) should be discontinued for at least 5 days before surgery (Class I; LOE B) and prasugrel (Effient) for at least 7 days (Class I; LOE: C) to limit blood transfusions. For urgent CABG, clopidogrel and ticagrelor should be discontinued for at least 24 hours to reduce major bleeding complications. Short-acting intravenous glycoprotein IIb/IIIa inhibitors (eptifibatide [Integrillin)] or tirofiban [Aggrastat]) should be discontinued for at least 2 to 4 hours before surgery and abciximab (Reopro) for at least 12 hours beforehand to limit blood loss and transfusions (Class I; LOE: B).

Guideline-directed post-operative medical therapy:

  • Beta blockers: Beta blockers should be reinstituted as soon as possible after CABG in all patients without contraindications to reduce the incidence or clinical sequelae of AF (Class I; LOE: B). Beta blockers should be prescribed to all CABG patients without contraindications at the time of hospital discharge (Class I).
  • Statins: All patients undergoing CABG should receive statin therapy, unless contraindicated (Class I; LOE: A). In patients undergoing CABG, an adequate dose of statin should be used to reduce low-density lipoprotein cholesterol to less than 100 mg/dL and to achieve at least a 30% lowering of low-density lipoprotein cholesterol (Class I; LOE: C).
  • ACE and ARB: ACE inhibitors or angiotensin-receptor blockers should be initiated postoperatively and continued indefinitely in CABG patients who were not receiving them preoperatively, who are stable, and who have an LVEF less than or equal to 40%, hypertension, diabetes mellitus, or chronic kidney disease, unless contraindicated (Class I; LOE: A). Angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARB) given before CABG should be reinstituted postoperatively once the patient is stable, unless contraindicated (Class I; LOE: B).
  • Insulin: The use of continuous intravenous insulin to achieve and maintain an early postoperative blood glucose concentration less than or equal to 180 mg/dL while avoiding hypoglycemia is indicated to reduce the incidence of adverse events, including deep sternal wound infection, after CABG (Class I; LOE: B).

Conduit Selection:

Venous conduits

Reversed greater saphenous vein (GSV) is the most commonly used conduit in coronary artery bypass graft surgery with more 90% utilization in CABG surgery. It has a reported 10-year angiographic patency rate of 50-60%. GSV has a 1-year graft failure rate of 15-20%. The recently published REGROUP trial randomized 1150 patients to open vs. endoscopic vein harvest technique and found that in experienced hands, both techniques had similar rates of major cardiac adverse events (HR, 1.12; 95% CI, 0.83 to 1.51; p=0.47) through nearly 3 years of follow-up, with similar rates of wound complications.

Arterial conduits

The left internal mammary artery (LIMA) anastomosed to the LAD has a reported 10-year angiographic patency rate of >95% and 20-year patency of >90%. The 2011 ACC/AHC Guideline on Coronary Artery Bypass Graft Surgery recommends the following:

  • If possible, the left internal mammary artery (LIMA) should be used to bypass the left anterior descending (LAD) artery when bypass of the LAD artery is indicated. (Class I; LOE: B)
  • The right internal mammary artery is probably indicated to bypass the LAD artery when the LIMA is unavailable or unsuitable as a bypass conduit. (Class IIa; LOE: C)
  • When anatomically and clinically suitable, use of a second internal mammary artery to graft the left circumflex or right coronary artery (when critically stenosed and perfusing LV myocardium) is reasonable to improve the likelihood of survival and to decrease reintervention. (Class IIa; LOE: B)

The right internal mammary artery (RIMA) has a reported angiographic patency of the RIMA at 10 years is 83-96% with patency directly related to the degree of proximal stenosis of the target vessel. Because the LIMA is preferentially anastomosed to the LAD, the RIMA is often anastomosed to a secondary target with less outflow than then LAD; furthermore, its trans-mediastinal course to left sided targets and higher rate of use as a free graft may also impact patency. A recent network meta-analysis of 4 randomized and 31 observational studies (n=149,902 patients) showed that use of saphenous vein (SV) was associated with higher long-term mortality compared with the RA (incidence rate ratio [IRR]), 1.23; 95% CI, 1.12–1.34) and RITA (IRR, 1.26; 95% CI, 1.17–1.35). The risk of deep sternal wound infection (DSWI) for SV was similar to RA but lower than RITA (odds ratio [OR], 0.71; 95% CI, 0.55–0.91). There were no differences for any outcome between RITA and RA, although DSWI trended higher with RITA (OR, 1.39; 95% CI, 0.92–2.1). The risk of DSWI in bilateral internal mammary artery studies was higher when the skeletonization technique was not used.

The radial artery (RA) has a reported angiographic patency rate of 80-90% at 7 to 10 years of follow-up. The radial artery is muscular artery which is prone to spasm in the perioperative period in the setting of significant competitive flow from native coronaries. Therefore, the radial artery is only recommended to bypass left-sided coronary lesions with severe (> 70%) stenosis and right sided coronary lesions with critical (> 90%) stenoses. The recently published RADIAL patient-level pooled analysis of 6 randomized prospective trials (n=1305 patients) compared radial to SVG conduit as second conduit after LIMA-LAD and found a significantly lower rate of death, MI or repeat revascularization at 5 years (HR, 0.67; 95% CI, 0.49 to 0.90; p=0.01) and significantly lower risk of occlusion (HR, 0.44; 95% CI, 0.28 to 0.70; p<0.001) at mean angiographic follow-up of 50 months. In of the graft analyzed, 75% of targets were left circumflex, 25% were to RCA.

The right gastroepiploic artery (RGEA) has reported angiographic patency rate of 66% at 10 years – likely because it is most often used to graft right-sided lesions and requires a high level of experience to perform. Similar to the radial artery, it should only be used to bypass critical (> 90%) right-sided stenoses or severe (>70%) left-sided stenoses, as addressed by the 2011 ACC/AHC Guideline on Coronary Artery Bypass Graft Surgery contraindication to bypassing lesions not meeting these anatomic criteria (Class III, Harm). The GEA generally is used to graft the RCA but can be used for distal circumflex targets.

Patient Scenarios and Intra-operative Complications

“In which patient would you consider performing total arterial revascularization?”

Complete arterial revascularization may be reasonable in patients ≤ 60 years of age with few or no comorbidities. (Class IIb; LOE: C).7 LIMA-LAD should be performed in every situation where LAD is to be bypassed. There are virtually no absolute or relative contraindications to utilizing the LIMA as one of the bypass conduits. Secondary target arterial conduits should be used only if the anatomic and physiologic criteria outlined above are fulfilled.

“When is coronary bypass indicated for patients undergoing non-coronary cardiac surgery?”

Coronary artery bypass grafting is recommended in patients undergoing noncoronary cardiac surgery with ³50% stenosis of the left main coronary artery or ³70% stenosis of other major coronary arteries (Class I; LOE: C).

“Your patient is found to have moderate aortic valve stenosis with a mean gradient of 28mmHg on preoperative echocardiography. He has no symptoms of aortic stenosis. Does this alter your operative plan?”

Patients undergoing CABG who have at least moderate aortic stenosis should have concomitant aortic valve replacement (Class I; LOE: C). Patients undergoing CABG who have mild aortic stenosis may be considered for concomitant aortic valve replacement when evidence (e.g., moderate–severe leaflet calcification) suggests that progression of the aortic stenosis may be rapid, and the risk of the combined procedure is acceptable (Class IIb; LOE: C). Please see Chapter 42 for management of ischemic mitral regurgitation at time of CABG.

“Your patient has a history of stroke and was found to have an 80% right carotid stenosis on preoperative screening carotid duplex. How does this change your management?”

In the CABG patient with a previous transient ischemic attack or stroke and a significant (50% to 99%) carotid artery stenosis, it is reasonable to consider carotid revascularization in conjunction with CABG. The sequence and timing (simultaneous or staged) of carotid intervention and CABG should be determined by the patient’s relative magnitudes of cerebral and myocardial dysfunction (Class IIb; LOE: C). In the patient scheduled to undergo CABG who has no history of transient ischemic attack or stroke, carotid revascularization maybe considered in the presence of bilateral severe (70% to 99%) carotid stenoses or a unilateral severe carotid stenosis with a contralateral occlusion (Class IIb; LOE: C). A multidisciplinary team approach (consisting of a cardiologist, cardiac surgeon, vascular surgeon, and neurologist) is recommended for patients with clinically significant carotid artery disease for whom CABG is planned (Class I; LOE: C). Regarding specifics of concomitant carotid and coronary intervention please see Chapter 44.

“During the left internal mammary harvest, the anesthesiologist tells you that the patient is hypotensive to 60/40, unresponsive to fluid and vasopressors and has new ST changes. What are your next steps?”

Give full dose heparin. Take down the mammary retractor and replace with a sternal retractor. Open the pericardium and cannulate the distal ascending aorta, right atrium and go on cardiopulmonary bypass. Once hemodynamic stability has been obtained, you may continue your internal mammary harvest and continue with the operation as planned.

Pearls/pitfalls

  • Know the pathophysiology of stable angina and initial diagnostic and pre-operative workup of patients with coronary artery disease.
  • Understand guideline-directed medical and surgical therapy for patients with coronary artery disease and know when CABG is indicated compared to PCI.
  • Understand the key operative steps for coronary artery bypass graft surgery, the various conduits available for use, and know the strengths and weaknesses of each conduit in specific clinical/anatomic situations.
  • Know the evidence-base for choosing specific conduits for bypass and their indications and contraindications.
  • Be able to recognize intra-operative complications and know how to manage them.

Suggested readings

  1. Fihn SD, Gardin JM, Abrams J, et al. 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and management of patients with stable ischemic heart disease. Circulation. 2012;126:e354–e471.
  2. Abu-Omar, Y., Mussa, S., Anastasiadis, K., Steel, S., Hands, L., and Taggart, D.P. Duplex ultrasonography predicts safety of radial artery harvest in the presence of an abnormal Allen test. Ann Thorac Surg. 2004; 77: 116–119
  3. Cohn JD, Korver KF. Selection of saphenous vein conduit in varicose vein disease. Ann Thorac Surg. 2006;81:1269–74.
  4. Götberg M, Cook CM, Sen S, et al. The Evolving Future of Instantaneous Wave-Free Ratio and Fractional Flow Reserve. J Am Coll Cardiol. Sep 2017, 70 (11) 1379-1402.
  5. Mohr FW, Morice MC, Kappetein AP, et al. Coronary artery bypass graft surgery versus percutaneous coronary intervention in patients with three-vessel disease and left main coronary disease: 5-year follow-up of the randomised, clinical SYNTAX trial. Lancet 2013;381:629-38.
  6. Panza JA, Ellis AM, Al-Khalidi HR, et al. Myocardial Viability and Long-Term Outcomes in Ischemic Cardiomyopathy. N Engl J Med 2019; 381:739-48.
  7. Hillis LD, Smith PK, Anderson JL, et al. 2011 ACCF/AHA guideline for coronary artery bypass graft surgery: a report of the ACCF/AHA Task Force on Practice Guidelines. J Am Coll Cardiol. 2011; 58(24): e123-210.
  8. Aldea GS, Bakaeen FG, Pal J, et al. The Society of Thoracic Surgeons Clinical Practice Guidelines on Arterial Conduits for Coronary Artery Bypass Grafting. Ann Thorac Surg 2016;101:801–9
  9. D’Agostino RS, Jacobs JP, Badhwar, V, et al. The Society of Thoracic Surgeons Adult Cardiac Surgery Database: 2018 Update on Outcomes and Quality. Ann Thorac Surg 2018;105:15–23.
  10. Gaudino M, Angelini GD, Antoniades C, et al. Off‐Pump Coronary Artery Bypass Grafting: 30 Years of Debate. J Am Heart Assoc. 2018 Aug 21;7(16):e009934.
  11. Lamy A, Devereaux PJ, Prabhakaran D, et al. CORONARY Investigators. Off‐pump or on‐pump coronary‐artery bypass grafting at 30 days. N Engl J Med. 2012; 366:1489–1497.
  12. Shroyer AL, Grover FL, Hattler B, et al. Veterans Affairs Randomized On/Off Bypass (ROOBY) Study Group. On‐pump versus off‐pump coronary‐artery bypass surgery. N Engl J Med. 2009; 361:1827–1837.
  13. Taggart DP, Benedetto U, Gerry S, et al. Arterial Revascularization Trial Investigators. Bilateral versus Single Internal-Thoracic-Artery Grafts at 10 Years. N Engl J Med 2019. 380:437-446.
  14. Farkouh ME, Domanski M, Sleeper LA, et al., for the Freedom Trial Investigators. Strategies for Multivessel Revascularization in Patients with Diabetes. N Engl J Med 2012; 367:2375-2384
  15. Velazquez EJ, Lee KL, Deja MA, et al. Coronary-artery bypass surgery in patient with left ventricular dysfunction. N Engl J Med 2011; 364:1607-16.
  16. Velazquez EJ, Lee KL, Jones RH, et al. Coronary-artery bypass surgery in patients with ischemic cardiomyopathy. N Engl J Med 2016; 374: 1511-20.
  17. Thuijs DJ, Bekker MW, Taggart DP, et al. Improving coronary artery bypass grafting: a systematic review and meta-analysis on the impact of adopting transit-time flow measurement. Eur J Cardiothorac Surg. 2019 Mar 25. pii: ezz075.
  18. Dearani JA, Axford TC, Patel MA, et al. Role of myocardial temperature measurement in monitoring the adequacy of myocardial protection during cardiac surgery. Ann Thorac Surg. 2001;72:S2235–44.
  19. R.D. Lopes, R.H. Mehta, G.E. Hafley, et al., for the PREVENT IV Investigators. Relationship between vein graft failure and subsequent clinical outcomes after coronary artery bypass surgery. Circulation. 125 (2012), pp. 749-756
  20. Halabi AR, Alexander JH, Shaw LK, et al. Relation of early saphenous vein graft failure to outcomes following coronary artery bypass surgery. Am J Cardiol. 2005;96(9):1254-9.
  21. Zenati MA, Bhatt DL, Bakaeen FG, et al., for the REGROUP Investigators. Randomized Trial of Endoscopic or Open Vein-Graft Harvesting for Coronary-Artery Bypass. N Engl J Med. 2019; 380:132-141.
  22. Loop FD, Lytle BW, Cosgrove DM, et al. Influence of the internal-mammary-artery graft on 10-year survival and other cardiac events. N Engl J Med. 1986 Jan 2;314(1):1-6.
  23. Sabik JF, Lytle BW, Blackstone EH, et al. Does Competitive Flow Reduce Internal ThoracicArtery Graft Patency? Ann Thorac Surg 2003;76:1490 –7.
  24. Gaudino M, Lorusso R, Rahouma M, et al. Radial Artery Versus Right Internal Thoracic Artery Versus Saphenous Vein as the Second Conduit for Coronary Artery Bypass Surgery: A Network Meta-Analysis of Clinical Outcomes. J Am Heart Assoc. 2019 Jan 22;8(2):e010839.
  25. Tatoulis J, Buxton BF, Fuller JA, et al. Long-term patency of 1108 radial arterial-coronary angiograms over 10 years. Ann Thorac Surg. 2009;88:23–9, discussion 29–30.
  26. Deb S, Cohen EA, Singh SK, et al., for the RAPS Investigators. Radial artery and saphenous vein patency more than 5 years after coronary artery bypass surgery: results from RAPS (Radial Artery Patency Study). J Am Coll Cardiol. 2012;60:28–35.
  27. Gaudino M, Benedetto U, Fremes S, et al. for the RADIAL Investigators. Radial-Artery or Saphenous-Vein Grafts in Coronary-Artery Bypass Surgery. N Engl J Med. 2018; 378:2069-2077.
  28. Suma H, Tanabe H, Takahashi A, et al. Twenty years experience with the gastroepiploic artery graft for CABG. Circulation. 2007;116 Suppl 11:I188–91.
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