42. Coronary Artery Bypass Graft and Percutaneous Coronary Intervention- Indications and Guidelines

Nika Samadzadeh Tabrizi MD, Rohun Bhagat MD, Faisal Bakaeen MD
Cleveland Clinic Foundation
July 31, 2024

Abbreviations & Definitions

CAD – Coronary artery disease
CABG – Coronary artery bypass grafting
EF – Ejection fraction
IMA – Internal mammary artery
LMA – Left main coronary artery
LAD – Left anterior descending artery
LV – Left ventricle
MAG – Multi-arterial grafting
MI – Myocardial infarction
PCI – Percutaneous coronary intervention
RA – Radial artery
RCT – Randomized controlled trial
STEMI – ST-elevation myocardial infarction
SVG – Saphenous venous graft

Trial Abbreviations

ART – Arterial Revascularization Trial

BEST – Coronary Artery Bypass Surgery and Everolimus-Eluting Stent Implantation in the Treatment of Patients with Multivessel Coronary Artery Disease

EXCEL – Evaluation of XIENCE versus Coronary Artery Bypass Surgery for Effectiveness of Left Main Revascularization

FREEDOM – Future Revascularization Evaluation in Patients with Diabetes Mellitus

ISCHEMIA – International Study of Comparative Health Effectiveness with Medical and Invasive Approaches

NOBLE – Nordic-Baltic-British Left Main Revascularization Study

PRECOMBAT – Bypass Surgery Versus Angioplasty Using Sirolimus Eluting Stent in Patients with Left Main Coronary Artery

RADIAL – Radial Artery Database International Alliance

RAPCO – Radial Artery Patency and Clinical Outcomes

REVIVED – Revascularization for Ischemic Ventricular Dysfunction

STITCH – Surgical Treatment for Ischemic Heart Failure

SYNTAX – SYNergy between Percutaneous Coronary Intervention with TAXus and Cardiac Surgery

Indications & Guidelines for Management by Grade/Stage of Disease

Ischemic heart disease is the most common form of heart disease, manifesting as a spectrum of symptoms, ranging from stable angina to acute MI. Many patients benefit from CABG or PCI, depending on their presentation, symptoms, and coronary anatomy. As such, it is critical to understand patient selection criteria thoroughly.

In the context of STEMI, PCI is generally the recommended intervention. CABG has a limited role in the acute setting, reserved for cases where revascularization is feasible when STEMI is accompanied by: 1) mechanical complications, 2) cardiogenic shock/hemodynamic instability, or 3) if a large myocardial area is at risk where PCI is unsuccessful or unfeasible. For STEMI patients with multivessel CAD, the priority is to treat the culprit lesion with PCI. The non-infarct-related artery may be subsequently addressed with staged PCI (Class I-A) or elective CABG (Class IIa-C).

In patients with non-STEMI or stable ischemia, the approach is more nuanced, contingent upon procedural risk, patient comorbidities, atherosclerotic burden, and disease complexity. CABG is the gold standard for patients with high-risk anatomical features, including patients with LMA disease, diabetes, or multivessel CAD.

Summary Table 1

Presentation and Severity of Disease Class of Recommendation
CABG PCI
STEMI
Ischemic symptoms Duration: < 12 hours IIa if PCI is not feasible/successful or significant residual CAD I
Ischemic symptoms Duration: 12 – 24 hours – IIa
Cardiogenic shock/hemodynamic instability, irrespective of timing I if PCI is not feasible/successful I
Mechanical complications (e.g., ventricular septal rupture, papillary muscle rupture) I –
Failed reperfusion after fibrinolytic therapy – I
Stable Ischemic Heart Disease
Angina refractory to medical management1,2 I IIa
LMA disease (≥ 50% stenosis) High anatomical complexity; Syntax score ≥ 331,2 I IIa
LMA disease (≥ 50% stenosis) Low anatomical complexity; Syntax score < 333,4 I* IIa
Two vessel disease (≥ 70% stenosis)1,2 With proximal LAD I I
Two vessel disease (≥ 70% stenosis)1,2 Without proximal LAD IIb I
Multivessel disease (with or without proximal LAD) LV dysfunction; EF < 50% I –
Multivessel disease (with or without proximal LAD) Normal LV function; EF > 50% (2011) I IIb
*2022 ESC/EACTS societal task force recommendations not reflected in the recent ACC/AHA/SCAI 2021 guidelines. Note: ACC/AHA/SCAI 2011 guidelines, which are endorsed by the Society of Thoracic Surgeons, are reflected here.

Supporting Evidence for Current Indications & Guidelines

  • LMA Disease with Low Anatomical Complexity: While CABG is the gold standard for LMA disease with high-risk anatomical features, the role of CABG in cases of low complexity is a subject of ongoing debate, and stems from several studies with variability in results, most recently the EXCEL RCT (2019).5 Presently four RCTs – SYNTAX, PRECOMBAT, NOBLE, and EXCEL – compare PCI to CABG in patients with low-to-medium anatomical complexity of the LMA, the aggregated results of which were compiled in a meta-analysis (2021). Subsequently, in 2022, the Joint ESC/EACTS task force provided updated recommendations and maintained that CABG is indicated for severe LMA disease with low anatomical complexity (Class Ia).3
  • EXCEL (2019)5: Compared PCI to CABG for LMA disease à PCI was associated with a significantly higher incidence of ischemia-driven repeat revascularization (16.9% vs. 10.0%, respectively) and all-cause mortality (13.0% vs. 9.9%) than CABG at 5 years. There were no significant differences in the incidence of stroke (2.9% and 3.7%), MI (10.6% and 9.1%), and cardiovascular death (5.0% and 4.5%).
  • Note: The initial report did not use the Universal Definition of Periprocedural MI; later analyses using this definition revealed a significantly higher rate of procedural MI with PCI compared to CABG (6.0% vs. 1.4%, respectively).6
  • Meta-analysis (2021)4: Compared PCI with drug-eluting stents to CABG in LMA disease à PCI was associated with a significantly higher incidence of spontaneous MI (6.2% vs. 2.6%, respectively) and repeat revascularization (18.3% vs. 10.7%) at 5 years, compared to CABG. There were no significant differences in the incidence of stroke (2.7% vs. 3.1%) and all-cause mortality (11.2% vs. 10.2%).
  • Note: Although overall survival was not significantly different, Kaplan-Meier survival curves crossed at 2 years, with a trend towards higher all-cause mortality for PCI at 5 years. Importantly, Bayesian analyses suggested an 85.7% probability that 5-year all-cause mortality was higher with PCI.
  • Multivessel Disease: The superiority of CABG over PCI for multivessel CAD has been established. The SYNTAX trial (2019) revealed a lower all-cause mortality with CABG compared to PCI over a 10-year follow-up period (21% vs. 28%, respectively).7 FREEDOM (2012)8 and BEST (2015)9 trials have demonstrated similar results in patients with or without diabetes. A recent meta-analysis (2023) reported aggregate outcomes of 6 RCTs, revealing CABG has a lower incidence of all-cause mortality, MI, and repeat revascularization at 5 years.10 CABG continues to be the standard of care (Class I) in multivessel CAD, especially in patients with diabetes mellitus.
  • Until 2021, multivessel CAD regardless of LV systolic function was agreed upon as a Class I recommendation for CABG (2011 AHA guidelines). However, the 2021 ACC/AHA/SCAI task force reclassified CABG to a Class I recommendation in patients with multivessel CAD with EF < 35%, Class IIa recommendation in patients with multivessel CAD with EF 30-50%, and Class IIb in patients with multivessel CAD with preserved EF. This change in recommendation is not supported by the Society of Thoracic Surgeons or the American Association of Thoracic Surgery because the available data does not support, and at times is contradictory to, the claims made by the 2021 ACC/AHA/SCAI guidelines and the subsequent 2023 Chronic Coronary disease guidelines.11,12
  • STITCH (2011)13: The largest RCT comparing CABG to medical management in patients with low LV function à CABG was associated with a significantly lower all-cause mortality (36% vs. 41%, respectively) and cardiovascular mortality (28% vs. 33%) at 5 years. At a 9.8-year follow-up, CABG was linked to 16% higher overall survival and 21% higher freedom from cardiovascular mortality than medical management.14
  • Note: PCI arm was not included in this trial, which has also been scrutinized due to a high 30-day mortality in CABG (3.6%), 26% cross-over rate, and significant advances to medical management since the trial’s initiation.
  • REVIVED (2022)15: First RCT comparing PCI and medical management to medical management alone in patients with severe ischemia (EF < 35%) à no significant differences in EF at 6 and 12 months and all-cause mortality or hospitalization due to heart failure at a median follow-up of 41 months.
  • ISCHEMIA (2020)16: Compared initial invasive strategy to conservative medical management in patients with diffuse CAD and moderate to severe ischemia à no significant differences in cardiovascular mortality or all-cause mortality at 5 years, with conservative strategy trending towards a higher risk of MI and cardiovascular death at ~2.5 years.
  • Note: This trial faces several controversies.11,12 First, it aimed at comparing invasive management (such as coronary angiography) to medical therapy (thus was not designed to compare CABG to PCI). It excluded those with LMA disease (> 50% stenosis on computed tomographic angiography), or EF < 35%. Further, only 50% of the population was truly managed according to the initial randomization and over 25% of patients in the invasive arm received suboptimal care (e.g., 8% of CABG patients didn’t receive an IMA graft, and only 36% had complete revascularization). Additionally, the ISCHEMIA population had a low-to-medium atherosclerotic burden with only 36% of patients having proximal LAD lesions with ≥ 50% stenosis.
  • Arterial Grafting: The superiority of arterial grafting over SVG has been recognized for decades. While SVG has a low long-term patency rate, ranging from 75-86% at 5 years to 55-60% at 10 years, arterial conduits remain patent for much longer. The LIMA has a patency rate of > 95% at 15 years, RIMA > 90% at 15 years, and RA > 90% at 10 years.
  • Therefore, IMA, preferably the left, is the gold standard for grafting the LAD (Class I), used in > 95% of cases due to its durability, which can be attributed to 1) a thin muscularis media, 2) high production of nitric oxide, 3) non-fenestrated internal elastic lamina, and 4) in-situ use. While the IMA is susceptible to competitive flow, this risk is reduced when the LAD is the target vessel, whereas RA is more prone to competitive flow and reserved for non-LAD vessels with very severe stenosis (Class I).
  • Multi-Arterial Grafting: The benefit of MAG with BIMAs or IMA-RA also stems from improved long-term patency and survival compared to SVG. The 2018 ESC/EACTS/STS guidelines strongly endorse MAG (Class IIa) for patients with appropriate life expectancy, typically < 70 years old.17 Yet, MAG is not widely adopted in the United States, performed in <15% of cases.18 This is partly due to most supporting data coming from observational studies, raising concerns that allocation bias and confounders may influence the reported outcomes.
  • In 2024, the largest retrospective study comparing MAG to single arterial grafting reported outcomes of > 1 million patients in the STS Database (2008 – 2019) who underwent ≥ 2-vessel CABG.19 Survival outcomes were significantly better with MAG during the early (0-1 year; HR 0.58), intermediate (1-5 years; HR 0.62), and late (5-12 years; HR 0.58) follow-up, and this association remained significant following inverse probability weighing-adjusted risk analysis. This survival benefit was seen across most demographics, comorbidities, and disease characteristics; however, single arterial grafting was associated with improved survival in patients with BMI > 40 kg/m2. To address the limitations of observational data, nevertheless, the ROMA RCT is expected to report primary data in 2028.20
  • While most experts recommend the use of MAG in selected patients with good life expectancy, the question of superiority between RA-IMA versus BIMA also remains unclear. Some RCTs favor RA-IMA.21,22 However, due to competitive flow, RA grafts should only be used to bypass lesions with severe stenosis or complete occlusion, whereas IMA is less vulnerable to competitive flow and can be used for lesser degrees of stenosis.
  • One controversial concern with the use of BIMA is the risk of mediastinal infection, particularly in patients with obesity or diabetes. However, recent literature shows mitigation of the mediastinitis risk with better preservation of sternal perfusion.23 The results of MAG are also dependent on surgeon experience and skill, especially with BIMA grafting, which is technically more demanding than RA use.19
  • ART (2019)26: The first and largest international RCT (n = 3,102) sufficiently powered to determine survival differences between BIMA and LIMA à Intention-to-treat analysis showed no significant differences in overall or event-free survival at 10 years.
  • Note: Limitations stem from a high frequency of RA grafting in both arms (20%) and a high cross-over rate from BIMA to single IMA (14%). The cross-over rate reached 100% among some surgeons. Among high-volume surgeons (enrolling > 50 cases), BIMA was associated with better overall survival, suggesting the importance of operator expertise.27 In an as-treated observational analysis, MAG with either LIMA-RA or BIMA was linked to superior all-cause mortality and major adverse events at 10 years.
  • RAPCO (2023)22,28: Compared MAG with RA to RIMA vs. SVG with long-term follow-up of 15 years à Among patients < 70 years old, RA-LIMA had significantly higher patency rates compared to BIMA at 10 years (89% vs. 80%, respectively), lower major adverse cardiovascular events at 15 years (48.5% vs 39.4%; p=0.04), and similar all-cause mortality at 15 years (30% vs. 22%; p=0.06).
  • Note: Major critiques of the trial include the use of RIMA as a free graft off the aorta and the center’s preference for the use of RA over RIMA in routine practice. Compared to SVG-LIMA, RA-LIMA had significantly higher patency rates at 10 years (85% vs. 71%), lower major adverse cardiovascular events at 15 years (60.2% vs 73.2%; p=0.04), and similar all-cause mortality at 15 years (52.2% vs. 63.4%; p=0.08). There were no significant differences in the risk of MI or revascularization at 15 years.
  • Radial, Veterans Affairs (2022)29: Post-hoc analysis of the largest trial (2011)30 comparing SVG to RA à no significant differences in graft patency or major adverse events at 1-year and overall survival at 18-year follow-up.

Summary Table 2

Single versus Multi-Arterial Grafting
No. Arterial Conduit(s) Class of Recommendation Conduit Type Class of Recommendation
Single2,24 I IMA I (left > right preferred)
Single2,24 I RA IIa*
Two2 IIa BIMA IIa
Two2 IIa IMA + RA IIa*
Target Recommendations
Conduit Target Contraindications (relative)
LIMA LAD Ipsilateral subclavian artery stenosis (in-situ grafts)
RIMA Any significantly diseased important target vessel Ipsilateral subclavian artery stenosis (in-situ grafts)
RA Non-LAD left-sided target ≥ 70% proximal stenosis Inadequate collateral flow to the hand; End-stage renal disease; Recent radial catheterization
RA Non-LAD right-sided target ≥ 90% stenosis, ≥ 1.5 mm in diameter Inadequate collateral flow to the hand; End-stage renal disease; Recent radial catheterization
*Utilizing the RA as a Class I recommendation in the ACC/AHA/SCAI 2021 guidelines – instead of Class IIa – is not supported by the American Association for Thoracic Surgery and the Society of Thoracic Surgeons, as it suggests that RA is similar to IMA and superior to BIMA.25 The RA is a valuable arterial conduit, and can be superior to saphenous vein, when utilized in patients with appropriate clinical and anatomic characteristics.

Ongoing Trials/Recent Publication

The ROMA Trial aims to address the methodological flaws in the topic of MAG by comparing the clinical outcomes of 4,370 patients across >80 international centers randomized to single arterial grafting or MAG. Surgeons were only included if they performed >250 CABGs with MAG. Primary outcomes are anticipated by 2028.20

Expert Commentary

Despite the controversy surrounding the recent cardiology guidelines, the evidence is robust in favor of CABG, which remains the standard of care in patients with multivessel disease with proximal LAD involvement and patients with LMA disease. The 2024 European guidelines have reaffirmed the superiority of CABG (class I recommendation) in 3-vessel CAD regardless of EF.31 The incremental advantage of CABG increases in high-complexity CAD (higher SYNTAX score) and diabetics. In addition, the use of MAG in select patients with favorable life expectancy is associated with improved long-term outcomes based on a wealth of observational data. Surgeon experience and skill are important outcome modifiers that may help explain the variability in outcomes, especially when it comes to RA vs. RIMA as a second arterial conduit to supplement the LIMA-LAD. Our approach is to bypass all important target vessels with arterial conduits, and in our experience, RIMA patency is more dependent on the target vessel than the inflow configuration.32-34

Sources

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