AIDA

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Wykrzykowska JJ et al. "Bioresorbable scaffolds versus metallic stents in routine PCI". The New England Journal of Medicine. 2017. 376(24):2319-2328.
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Clinical Question

In patients with stable or unstable coronary artery disease (CAD) undergoing percutaneous coronary intervention (PCI), are bioresorbable scaffolds superior to standard drug-eluting stents (DES) with regard to target-vessel failure?

Bottom Line

In patients with stable or unstable CAD undergoing PCI, bioresorbable scaffolds are associated with similar rates of target-vessel failure (defined as death, target-vessel MI, target-vessel revascularization) as DES at 2 years. Importantly, scaffolds were associated with a 2.6% absolute increase in probable or definite device thrombosis compared to DES.

Major Points

Although current second-generation DES are the best established and most efficacious means of achieving and maintaining coronary artery patency in the setting of obstructive CAD, they are still associated with an ongoing risk of stent thrombosis (approximately 0.1-0.2% per year) and in-stent restenosis (2-3% per year). Theoretically, recently developed biosorbable metallic scaffolds leave no permanent implant and thus may allow for better restoration of natural vessel function after revascularization. The ABSORB-III trial demonstrated noninferiority with the bioresorbable scaffold versus everolimus-eluting DES with regard to target-vessel patency at 1 year. However, multiple observational studies as well as longer-term follow up of the related ABSORB II trial suggest that scaffolds may be associated with higher medium-term device failure rates than DES. [1][2] Nevertheless scaffolds have been approved for use by the FDA and the EU and have already begun to achieve significant clinical use. A longer-term RCT investigating the comparative efficacy and safety of scaffolds vs. DES was needed.

The 2017 Amsterdam Investigator-Initiated Absorb Strategy All-Comers Trial (AIDA) trial randomized 1845 patients with stable or unstable CAD with an indication for revascularization to either bioresorbable scaffold or second-generation DES. 60% of patients were presenting with ACS while the other 40% underwent revascularization for chronic stable angina. Revascularization success was high in both groups (97% with DES and 90% with scaffold), although the numerical difference was statistically significant. At 2 years, the primary endpoint of target-vessel failure (death, target-vessel MI, target-vessel revascularization) was similar in both groups, although there was a statistically significant 2.3% absolute increase in MIs associated with scaffold. Patients randomized to scaffold insertion also suffered a 2.6% absolute increase in probable or definite device thrombosis (31 events in scaffold group vs. 8 in DES group) which likely led to the increased rate of MIs.

The results of the AIDA trial provide strong evidence that the signal for increased thrombosis rates with scaffolds in the medium-term suggested by observational studies is real and likely clinically significant, particularly given the known excess morbidity/mortality associated with device thrombosis. Although further refinement of scaffold technology may eventually result in resorbable devices that allow for improved native vessel function after revascularization, at this time there is no established role for bioresorbable scaffolds in obstructive CAD.

Guidelines

As of June 2017, no guidelines have been published that reflect the results of this trial.

Design

  • Prospective, multi-center, single-blind, randomized controlled trial
  • N=1845
    • Scaffold (n=924)
    • DES(n=921)
  • Setting: 5 centers in the Netherlands
  • Enrollment: August 28, 2013 to December 27, 2015
  • Duration follow-up: 2 years
  • Analysis: Intention-to-treat
  • Primary outcome: Target-vessel failure (death, target-vessel MI, target-vessel revascularization)

Population

Inclusion Criteria

  • Patient is a candidate for DES based on consensus guidelines

Exclusion Criteria

  • Age < 18 years
  • Bifurcation lesion in which a two device strategy is planned
  • Unsuccessful predilation of one or more lesions to be treated
  • Planned treatment of in-stent restenosis
  • One or more lesions treated with scaffold/stent diameter smaller than 2.5mm or greater than 4.0mm
  • One or more lesions treated with scaffold/stent length greater than 70mm and/or overlapping of four or more scaffolds/stents
  • Known hypersensitivity to aspirin, both bivalirudin and heparin, antiplatelet medication specified for use in the study, everolimus, or other medication present in stent that cannot be pre-treated
  • Pregnant or nursing subjects and those who plan on becoming pregnant up to 2 years following the index procedure
  • Life expectancy < 1 year
  • Unable to meet clinical follow-up

Baseline Characteristics

From the scaffold group

  • Demographics: age 64.3, male 72.5%
  • Co-morbidities: DM 18.5%, HTN 50.9%, HLD 37.6%, smoker 28.6%, CKD 7.6%, LVEF < 30% 2.4%, stroke/TIA 5.0%, PAD 7.0%, MI 18.0%, previous PCI 21.9%, previous CABG 4.1%
  • Presentation: STEMI 26%, NSTEMI 20.0%, UA 7.6%, stable angina 39.1%, SYNTAX score 13.2
  • Procedural: Treated lesions 1.34, # devices 1.54, procedure time 49min, contrast used 160cc, predilation 98.6%, procedural success 90.2%

Interventions

  • Randomized 1:1 to scaffold or DES.
  • Patients (but not providers or operators) were blinded to device assignment.
  • During the first year of enrollment, post-dilation of scaffold was not required (done in 63% of patients). Following October 1, 2014, post-dilation was required based on new manufacturer guidelines.
  • Dual antiplatelet therapy and other medications were administered before the procedure in accordance with guidelines of the ESC and device manufacturer's instructions.
  • Clinical follow-up was conducted through telephone contact and was scheduled at 30 days, 180 days, and at 1, 2, 3, 4, and 5 years after the procedure.
  • An independent clinical-events committee staffed by the contract research organization Cardialysis adjudicated events according to the definitions of the Academic Research Consortium and the Third Universal Definition of Myocardial Infarction.
  • Quantitative coronary angiography was performed with the use of dedicated software on the post-procedural angiograms obtained from the patients in the scaffold group.

Outcomes

Comparisons are scaffold vs. DES

Primary Outcomes

Target-Vessel Failure (death, nonfatal target-vessel MI, or target vessel-revascularization)
105 (11.7%) vs. 94 (10.7%) [HR 1.12, 95% CI 0.85-1.48, p=0.43]

Secondary Outcomes

All-cause death
32 (3.5%) vs. 43 (4.3%) [HR 0.74, 95% CI 0.47-1.17, p=0.19]
Myocardial infarction
62 (7.1%) vs. 41 (4.2%) [HR 1.52, 95% CI 1.02-2.25, p=0.04]
Any revascularization
115 (13.2%) vs. 103 (11.6%) [HR 1.11, 95% CI 0.85-1.45, p=0.43]

Subgroup Analysis

  • No interaction with respect to device thrombosis was seen between the study groups and presenting symptoms, age, cardiovascular risk factors, lesion characteristics, or time of randomization.

Adverse Events

Definite device thrombosis
27 (3.1%) vs. 5 (0.6%) [HR 5.39, 95% CI 2.08-14.00, p<0.001]
Definite or probable device thrombosis
31 (3.5%) vs. 8 (0.9%) [HR 3.87, 95% CI 1.78-8.42, p<0.001]
Any device thrombosis
37 (4.1%) vs. 20 (2.5%) [HR 1.85, 95% CI 1.08-3.19, p=0.02]

Criticisms

  • Non-blinding of operators/providers allows for possible ascertainment bias. However, blinded independent outcomes assessment should largely mitigate this bias.
  • Relatively limited follow-up period of nearly 2 years limits ability to detect differences in outcomes over the longer term with scaffold versus stenting.

Funding

  • Study supported by an unrestricted educational grant from Abbott Vascular (maker of scaffold)

Further Reading

  1. Serruys PW et al. Comparison of an everolimus-eluting bioresorbable scaffold with an everolimus-eluting metallic stent for the treatment of coronary artery stenosis (ABSORB II): a 3 year, randomised, controlled, single-blind, multicentre clinical trial. Lancet 2016. 388:2479-2491.
  2. Fam JM et al. Initial experience with everolimus-eluting bioresorbable vascular scaffolds for treatment of patients presenting with acute myocardial infarction: a propensity-matched comparison to metallic drug eluting stents 18-month follow-up of the BVS STEMI first study. EuroIntervention 2016. 12:30-7.