Clinical, Angiographic, and Procedural Correlates of Very Late Absorb Scaffold Thrombosis: Multistudy Registry Results.

OBJECTIVES: The aim of this study was to identify independent correlates of very late scaffold thrombosis (VLST) from an analysis of consecutively treated patients from 15 multicenter studies.

BACKGROUND: Recent analyses suggest an increased risk for VLST with the Absorb Bioresorbable Vascular Scaffold compared with drug-eluting stents, but insights as to correlates of risk are limited.

METHODS: A total of 55 patients were identified with scaffold thrombosis. They were matched 2:1 with control subjects selected randomly from patients without thrombosis from the same study. Quantitative coronary angiography was available for 96.4% of patients. Multiple logistic and Cox regression analysis were used to identify significant independent outcome correlates from 6 pre-specified characteristics.

RESULTS: Patients had scaffold thrombosis at a median of 20 months (interquartile range: 17 to 27 months). Control subjects were followed for 36 months (interquartile range: 24 to 38 months). For the combined groups, reference vessel diameter (RVD) was 2.84 ± 0.50 mm, scaffold length was 26 ± 16 mm, and post-dilatation was performed in 56%. Univariate correlates of thrombosis were smaller nominal scaffold/RVD ratio (linear p = 0.001; ratio <1.18:1; odds ratio: 7.5; p = 0.002) and larger RVD (linear p = 0.001; >2.72 mm; odds ratio: 3.4; p = 0.001). Post-dilatation at ≥16 atm, post-dilatation balloon/scaffold ratio, final percentage stenosis, and dual antiplatelet therapy were not correlated with VLST. Only scaffold/RVD ratio remained a significant independent correlate of VLST (p = 0.001), as smaller ratio was correlated with RVD (p < 0.001). Post hoc analysis of 8 other potential covariates revealed no other correlates of outcome.

CONCLUSIONS: In the present analysis, the largest to date of its type, relative scaffold undersizing was the strongest determinant of VLST. Given current understanding of "scaffold dismantling," this finding likely has ramifications for all bioresorbable scaffolds.