After Absorb Stent Absorbs, Vessel Rebounds

WASHINGTON — The first-generation Absorb bioresorbable vascular scaffold (BRS or BVS) was associated with better coronary function at the level of the large epicardial vessel at 3 years, according to the ABSORB II Physiology Substudy.

Compared with the Xience everolimus-eluting drug-eluting stent (DES), patients randomized to the Absorb BRS had:

• More effective blood transportation (epicardial conductance 11.52 vs 5.42 cm/s/mmHg, P=0.048)
• Better viscoelasticity of the treated segment, measured both by forward compression wave (5.4 x 10⁶ vs 3.7 x 10⁶ Wm^-2s^-1, P=0.024) and forward expansion wave (1.6 x 10⁶ vs 0.7 x 10⁶ Wm^-2s^-1, P=0.047)

Three years is the expected time for complete resorption of the Absorb scaffold. Javier Escaned, MD, PhD, of Madrid’s Hospital Clinico San Carlos, presented the findings at the annual Cardiovascular Research Technologies meeting.

The first-generation Absorb BRS was pulled from the market when study after study suggested no improvement in clinical outcomes over the metallic Xience DES but rather signaled excess device thrombosis.

Still, “these findings support the existence of favorable long-term differences in [the] vascular mechanics of BRS-treated vessels, as compared with those treated with metallic stents,” Escaned concluded.

However, BRS and DES groups were similar in their microvascular function, as determined by the degree of microvascular structural remodeling (microcirculatory conductance), extravascular compression of capillaries (zero flow pressure), and capillary density downstream of the treated vessel (backward expansion wave), Escaned told the audience.

The ABSORB II substudy was based on patients at three Dutch centers getting scheduled follow-up after receiving Absorb (n=13) or Xience (n=16). A blinded core laboratory performed the analyses.

While there were no differences between groups at baseline, the BVS arm was left with larger in-stent stenoses after percutaneous coronary intervention (16% vs 8% for DES, P=0.004) and at 3 years continued to show greater in-stent stenosis on angiography (22% vs 13%, P=0.01).

Late loss and fractional flow reserve were the same at 3 years regardless of the assigned treatment.

“The findings of the study confirm that, once the scaffold resorption process is completed … the coronary wall in segments treated with BRS recover some of the normal characteristics of the epicardial vessels,” according to a press release on the study.

“Further research is required to establish whether this phenomenon results in a clinical benefit for the patients treated with BRS. Preserved wave transmission and vessel pulsatility might protect against disease progression by mechanisms mediated by endothelial shear stress and mechanotransduction,” the statement continued.