ABSORB: Bioresorbable scaffold yields encouraging outcomes

A bioresorbable vascular scaffold was associated with stable luminal dimensions and low restenosis rates at 3 years in the ABSORB trial.

The aim of the study was to evaluate multimodality imaging of the Absorb bioresorbable everolimus-eluting vascular scaffold (Abbott Vascular). The analysis included two patient cohorts that underwent serial investigation at 6 and 24 months (n=45) or 12 and 36 months (n=56).

The techniques used to evaluate all patients included serial invasive imaging, specifically quantitative coronary angiography, along with IVUS, radiofrequency backscattering (IVUS-VH) and optical coherence tomography.

Results indicated that late luminal loss did not change during the period between 1 and 3 years. At 6 months, late luminal loss of 0.19 mm was reported. Loss was 0.27 at 1 year, 0.27 at 2 years and 0.29 at 3 years.

Among all patients, a 6% in-segment angiographic restenosis rate was reported at the 3-year mark.

Results at 2 years after IVUS indicated several areas of enlargement, including mean lumen, scaffold plaque and vessel area. Between the second and third year, mean lumen and scaffold area remained stable, according to the findings. However, during that time, a significant reduction in plaque behind the struts was reported. This outcome included a trend toward adaptive restrictive remodeling of the external elastic membrane.

A decrease from 23.1% to 10.4% occurred with regard to hyperechogenicity of the vessel wall, which the researchers noted is a surrogate for the bioresorption process. They added that there was also a reduction in “radiofrequency backscattering for dense calcium and necrotic core.”

OCT results demonstrated a significant increase in the count of strut cores at 3 years. This may have reflected the dismantling of the scaffold, according to the researchers, who added that 98% of the struts were covered.

A 10% MACE rate at 3 years was reported among all 101 patients in the cohort.

Gregg W. Stone

Gregg W. Stone, MD, of Columbia University Medical Center, New York Presbyterian Hospital and the Cardiovascular Research Foundation, noted in an accompanying editorial that little could be inferred from the event rates due to the small patient cohort, but noted that the rates may be similar to what could be expected for everolimus-eluting stents.

“Similarly, the dramatic images and unique vascular responses after [bioresorbable everolimus-eluting vascular scaffold] implantation, as brilliantly elucidated by the imaging studies of Serruys and colleagues, are fascinating the subspecialty of interventional cardiology — we have never seen anything like this before and the clinical potential for this innovative technology is alluring,” Stone wrote. “However, our excitement must be tempered by the recognition that, compared to contemporary metallic DES, current [bioresorbable everolimus-eluting vascular scaffolds] may have greater crossing profiles and reduced deliverability; thicker struts with the potential for greater side branch compromise and (theoretically) delayed re-endothelialization; a more limited expansion range (with increased susceptibility to fracture); less secure retention on the delivery balloon; and somewhat greater recoil requiring more aggressive lesion preparation.”

These issues will likely be rectified in future generations of the device, according to Stone. Large scale randomized trials will be necessary to demonstrate their clinical benefit.

“If these goals are met, Absorb (and the conceptual framework of [bioresorbable everolimus-eluting vascular scaffolds]) will become established as the fourth revolution in interventional cardiology, and the therapeutic landscape for patients with atherosclerotic [CAD] will be radically transformed,” Stone wrote.

For more information:

Serruys PW. EuroIntervention. 2014;9:1271-1284.

Stone GW. EuroIntervention. 2014;9:1255-1257.

Disclosure: The researchers report financial disclosures with Abbott Vascular and Biotronik. Stone reports financial disclosures with Boston Scientific and REVA Medical.