Differences in neointimal thickness between the adluminal and the abluminal sides of malapposed and side-branch struts in a polylactide bioresorbable scaffold: evidence in vivo about the abluminal healing process.

OBJECTIVES: The goal of this study was to describe the neointimal healing on the abluminal side (ABL) of malapposed (ISA) struts and nonapposed side-branch (NASB) struts in terms of coverage by optical coherence tomography (OCT) and in comparison with the adluminal side (ADL).
BACKGROUND: The neointimal healing on the ABL of ISA and NASB struts has never to our knowledge been explored in vivo and could be involved in the correction of acute malapposition. The bioresorbable vascular scaffold (BVS) is made of a translucent polymer that enables imaging of the ABL with OCT.
METHODS: Patients enrolled in the ABSORB B (ABSORB Clinical Investigation Cohort B) study were treated with implantation of a BVS and imaged with OCT at 6 months. Thickness of coverage on the ADL and ABL of ISA and NASB struts was measured by OCT.
RESULTS: Twenty-eight patients were analyzed; 114 (2.4%) struts were malapposed or at side branches. In 76 ISA struts (89.4%) and 29 NASB struts (100%), the thickness of ABL coverage was >30 μm. Coverage was thicker on the ABL than on the ADL side (101 vs. 71 μm; 95% confidence interval [CI] of the difference: 20 to 40 μm). In 70 struts (60.7%, 95% CI: 50.6% to 70.0%), the neointimal coverage was thicker on the ABL, versus only 20 struts (18.5%, 95% CI: 11.6% to 28.1%) with thicker neointimal coverage on the ADL side (odds ratio: 3.35, 95% CI: 2.22 to 5.07).
CONCLUSIONS: Most of the malapposed and side-branch struts are covered on the ABL side 6 months after BVS implantation, with thicker neointimal coverage than on the ADL side. The physiological correction of acute malapposition involves neointimal growth from the strut to the vessel wall or bidirectional. (ABSORB Clinical Investigation, Cohort B [ABSORB B]; NCT00856856).