Serial in vivo intravascular ultrasound-based echogenicity changes of everolimus-eluting bioresorbable vascular scaffold during the first 12 months after implantation: Insights from the ABSORB B trial
Because the bioresorption of the ABSORB bioresorbable vascular scaffold (Abbott Vascular, Santa Clara, California) is characterized by a diminishing gray-level intensity of the struts over time, the evaluation of quantitative changes in hyperechogenicity can be useful to follow the in vivo degradation of the scaffold. Whereas the first ABSORB generation showed at 6 months a 50% reduction in hyperechogenicity, the second ABSORB generation (1.1), designed to prolong the duration of luminal scaffolding, showed a 15% and 20% reduction in hyperechogenicity at 6 and 12 months, respectively, compared with post-implantation. These findings confirm the value of the manufacturing changes and suggest a slower degradation rate of the scaffold. This study sought to investigate quantitative and homogeneity differential echogenicity changes of the ABSORB scaffold (1.1) during the first year after implantation. The imaging of the ABSORB bioresorbable vascular scaffold degradation by intravascular ultrasound (IVUS) has previously demonstrated diminishing gray-level intensity of the struts over time that can be evaluated by IVUS-based differential echogenicity. The first generation of ABSORB (1.0) showed a 50% reduction in hyperechogenicity at 6 months and restoration of the pre-ABSORB implantation values at 2 years. The second generation of ABSORB (1.1), investigated in the ABSORB B trial, was modified to prolong the duration of luminal scaffolding. A total of 63 patients were examined by IVUS immediately post-implantation and at 6-month (Cohort B1, n = 28) or 12-month (Cohort B2, n = 35) follow-up. IVUS-based tissue composition analysis software was used to quantify changes in hyperechogenicity over time in the scaffolded regions. Relative changes in hyperechogenicity were calculated as: 100 × (% hyperechogenicity at follow-up - % hyperechogenicity at baseline)/% hyperechogenicity at baseline. At 6- and 12-month follow-up, there was a 15% (from 22.58 ± 9.77% to 17.42 ± 6.69%, p = 0.001) and 20% (from 23.51 ± 8.57% to 18.25 ± 7.19%, p < 0.001) reduction in hyperechogenicity, respectively, compared with post-implantation values. No difference in hyperechogenicity changes were observed between the proximal, medial, or distal part of the scaffolded segment. Quantitative differential echogenicity changes of the ABSORB scaffold (1.1) during the first 12 months after implantation are lower compared with those previously observed with its first generation (1.0), confirming the value of the manufacturing changes and suggesting a slower degradation rate of the scaffold.