The 2021 American guidelines on coronary artery revascularization, reflecting new evidence from the evolving field, updated key recommendations on coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI) for a wide spectrum of heart patients.

The updated 109-page guideline – drafted by an interdisciplinary 22-member writing committee – was jointly published by the American College of Cardiology (ACC), American Heart Association (AHA), and Society for Cardiovascular Angiography and Interventions (SCAI) in Circulation last year on Dec 9.

Advocated foremost were the concepts of multidisciplinary heart teams to foster communication between clinicians and consistent treatment strategies for patients based on clinical indications, not race or gender, especially when the optimal strategy is debatable.

“For patients where the optimal coronary revascularization strategy is unclear, a multidisciplinary Heart Team approach is recommended,” the writing committee wrote. “Treatment decisions should be patient-centered, incorporate patient preferences and goals and include shared decision-making.”

“Revascularization decisions in patients with diabetes and multivessel coronary artery disease (CAD) are optimized by the Heart Team approach. Patients with diabetes and triple-vessel disease should undergo surgical revascularization; PCI may be considered if they are poor candidates for surgery.”

The updated recommendations replace those of seven prior guidelines including the 2011 ACCF/AHA guideline for CABG; 2011 and 2015 ACCF/AHA/SCAI guidelines for PCI; 2012 ACCF/AHA/ACP guideline for stable ischemic heart disease; 2013 ACCF/AHA guideline for ST-segment elevation myocardial infarction (STEMI); 2014 AHA/ACC guideline for non-STEMI acute coronary syndrome (NSTEMI-ACS); and 2015 ACC/AHA/SCAI focused update on PCI in STEMI patients.

New and updated strategies recommended for revascularization, imaging, DAPT, risk scores

Among key updates, the 2021 ACC/AHA/SCAI guidelines on coronary artery revascularization featured revised recommendations on coronary revascularization, imaging strategies, post-revasc medical therapies and risk scores.

For coronary revascularization, recommendations were divided by disease groups that included STEMI (of both infarct and non-infarct arteries), NSTE-ACS, stable ischemic heart disease (SIHD), complex disease, and special populations like pregnant, older or chronic kidney disease (CKD) patients.

Major recommendations for SIHD were further divided into groups like multivessel coronary artery disease (MVCAD); left ventricular (LV) dysfunction and MVCAD; left main CAD (LMCAD); stenosis in the proximal LAD artery; and 1- or 2-vessel disease not involving the proximal LAD.

For SIHD patients with significant LM stenosis, surgery with CABG was recommended over optimal medical therapy (OMT) to improve survival (COR 1; B-R). In the same patient group, PCI was recommended as a reasonable strategy to improve survival when it could provide outcomes comparable to CABG (COR 2a; B-NR).

For SIHD patients with MVCAD and severe LV systolic dysfunction (LVEF < 35%), CABG was strongly recommended to improve mortality outcomes (COR 1; B-R). CABG was deemed reasonable (Class 2a) for select SIHD patients with MVCAD and mild-to-moderate LV dysfunction (LVEF 35-50%).

For SIHD patients with triple-vessel disease, normal ejection fraction (EF) and significant stenosis in 3 major coronary arteries (with or without proximal LAD), CABG was recommended as a reasonable strategy to improve survival if the patient had anatomy favorable for surgery (COR 2b; B-R).

For the same 3-vessel patient group, the usefulness of PCI to improve survival was “uncertain” but obtained an endorsement equal to CABG (COR 2b; B-R).

Coronary revascularization with either strategy could be considered to treat significant stenosis of the proximal LAD artery in SIHD patients with normal LVEF (Class 2b; B-R).

Both PCI and CABG were not recommended in SIHD patients with normal LVEF and 1- or 2-vessel CAD not involving proximal LAD (Class 3; B-R) or when 1 or more coronary arteries are anatomically or functionally insignificant (>70% diameter of non-LM coronary artery stenosis; FFR > 0.80) (Class 3; B-NR).

On novel recommendations for PCI, the guideline endorsed staged PCI for significantly stenosed nonculprit arteries in select hemodynamically stable STEMI and multivessel disease patients to improve survival and MI outcomes (COR 1; A).

PCI of the nonculprit artery at the time of intervention was deemed “less clear” but considerable at the time of primary PCI in select stable STEMI patients when uncomplicated revascularization of the culprit artery, low-complexity nonculprit disease and normal renal function are present (COR 2b; B-R).

Routing PCI of the nonculprit artery at the time of primary PCI was contraindicated for STEMI patients with cardiogenic shock (COR 3; B-R).

On imaging strategies, fractional flow reserve (FFR) and instantaneous wave-free ratio (IFR) were strongly recommended (COR 1; A) for patients with angina, undocumented ischemia and angiographically intermediate stenosis.

Both FFR and IFR were contraindicated (COR 3; B-R) in stable patients with angiographically intermediate stenoses (FFR >0.80; IFR >0.89).

For post-PCI maintenance therapy, a shorter period of dual antiplatelet therapy (DAPT) was deemed reasonable to reduce bleeding risk in SIHD patients (COR 2a; A). Shorter DAPT entailed 1- to 3- months of DAPT followed by discontinuing aspirin and resuming P2Y12 inhibitor monotherapy.

On access routes, radial access was strongly recommended over femoral access for both CABG (COR 1; B-R) and PCI (COR 1; A) to reduce bleeding and vascular complications.

For CABG, Class 1 recommendations were given to both radial access (B-R) and internal mammary artery (IMA) grafting (B-NR). Bilateral internal mammary artery (BIMA) received a Class 2a recommendation (B-NR).

On risk scores to guide treatment decisions, the Society of Thoracic Surgeons (STS) score received a strong Class 1 recommendation (B-NR) while the SYNTAX score obtained a weaker Class 2b recommendation (B-NR) due to uncertainty of usefulness.

SIHD revasc recommendations spark initial controversy, result in eventual consensus

Of recommendations for SIHD patients, those on triple-vessel CAD incited heavy criticism from cardiac surgeons last year, causing a rift between medical specialties that panned out to an agreement that PCI and CABG are complementary, not antagonistic, strategies.

Starting with the American Association for Thoracic Surgery (AATS) and Society of Thoracic Surgeons (STS) on Dec 23, major surgical societies from the US, Europe, Latin America and Argentina, India, and Japan objected to the American guidance in respective letters published in international medical journals.

Most protested were the recommendations on coronary revascularization compared to medical therapy that seemed to favor PCI over CABG for SIHD patients without sufficient evidence.

Key points of opposition, stated by the AATS/STS and other surgical communities, included problems with the ISCHEMIA trial that was used as primary evidence to support stronger recommendations for PCI and weaker ones for CABG.

Surgeons pointed out in respective publications that well-known randomized controlled trials (RCTs) like SYNTAX, EXCEL and NOBLE “clearly demonstrated” the superiority of CABG over PCI for repeat reinterventions and post-procedural MI that were not reflected in the guidelines.

At TCTAP 2022, cardiac surgeon S. Christopher Malaisrie, MD (Northwestern University Feinberg School of Medicine, Illinois, USA) reemphasized the survival benefits of CABG for patients with MVD and LMCAD despite the recent CABG downgrades.

“Evidence demonstrates survival benefits with CABG over OMT in multivessel disease and even more in LMCAD,” Malaisrie said. “But American and European clinical practice guidelines interpreted data differently, appearing to undervalue the benefits of CABG, and surgical associations have not endorsed their respective continental guidelines that discount ‘old’ data and undervalue new surgical techniques.”

Addressing the controversy, interventional cardiologist Sripal Bangalore, MD (New York University School of Medicine, New York, USA) – who served on the 2021 ACC/AHA guideline writing committee – explained at TCTAP 2022: “The recommendations on triple-vessel disease generated the controversy, and the notion was that the guideline committee simply downgraded CABG recommendations.”

“But the committee considered various factors like recent studies that showed no survival benefit with revascularization compared to OMT,” Bangalore said. “There was a clear benefit with CABG in triple-vessel disease at 6-months when comparing surgery to no surgery in the 1980s, but fast forward to the BARI 2D trial in 2009 and results showed – on purely the mortality endpoint for CABG, not PCI – no difference between CABG and medical therapy.”

“Recent SIHD studies on revascularization also show no improvement in cardiac death with revascularization compared to OMT; however, we’re not saying do not revascularize for triple-vessel disease,” he said. “There are other benefits like preventing CV events including spontaneous MI and improving QoL for symptomatic patients.”

In a separate session, Bangalore further stressed guideline-directed medical therapy (GDMT) as the “backbone” of all treatment: “One of the biggest problems today is people painting broad strokes of CABG and revascularization as superior to OMT based on the composite endpoint without looking at individual endpoints. RCTs results from the OMT era on the mortality endpoint send a consistent message.”

Also a member of the guideline writing committee, cardiac surgeon Mario F.L. Gaudino, MD (Weill Cornell Medical College, Cornell University, New York, USA) said at TCTAP 2022: “We are essentially comparing two different interventions.”

“Surgery has consistently shown similar mortality and reduced risk of MI and repeat revascularization for patients with MVD and LM disease amenable by either strategy,” Gaudino said. “PCI demonstrated comparable results to surgery for the first two years as a less invasive strategy.”

“A difference favoring surgery is evident for patients with diabetes and complex disease as well as long-term clinical outcomes; however, CABG is associated with higher periprocedural risk and longer recovery rates,” he said.

“Exempting the relative risk, the absolute difference between the two is small, which becomes evident in long-term follow-up. Ultimately, PCI and CABG are two complementary interventions performed for different patients and different aims.”