Characteristics, Predictors, and Mechanisms of Thrombosis in Coronary Bioresorbable Scaffolds: Differences Between Early and Late Events.

OBJECTIVES: The study sought to investigate the incidence, characteristics, predictors, and possible mechanisms of early and 3-year coronary scaffold thrombosis (ScT).

BACKGROUND: An increased incidence of both early and late ScT has been shown in randomized trials.

METHODS: Consecutive patients were enrolled in a single-center registry. Quantitative coronary angiography was performed. Incidence and predictors of ScT were assessed with Kaplan-Meier and Cox regression analyses.

RESULTS: A total of 657 patients (63 ± 12 years of age, 79% men, 21% diabetic, 64% acute coronary syndrome) who received 925 coronary bioresorbable scaffolds (BRS) (Abbott Vascular, Santa Clara, California) between May 2012 and January 2015 were enrolled. Clinical and procedural characteristics and outcome data at 1,076 (interquartile range: 762 to 1,206) days (3-year follow-up rate 93%) were collected. Twenty-eight ScTs were recorded: 14 early (Kaplan-Meier estimate: 2.2%), 5 late (Kaplan-Meier estimate: 0.9%), and 9 very late (Kaplan-Meier estimate: 1.7%). The incidence of ScT followed a U-shaped curve with highest incidence at the extremes of the distributions of reference vessel diameter (RVD) and the ratio of BRS nominal diameter to RVD. At quantitative coronary angiography, RVD (hazard ratio [HR]: 0.14; 95% confidence interval [CI]: 0.04 to 0.49) and BRS oversizing (ratio of BRS nominal diameter to RVD >1.15; HR: 107.40; 95% CI: 9.20 to 1,261.30) emerged as potent predictors of early ScT. RVD (HR: 9.55; 95% CI: 3.90 to 23.42) and BRS undersizing (ratio of BRS nominal diameter to RVD <0.85; HR: 0.0004; 95% CI: 0.0000 to 0.0400) predicted late or very late ScT (all p < 0.0001). The incidence of both early and late or very late ScT were lower (∼80% reduction) when an optimal implantation technique was used. The most important factor appeared to be vessel and BRS sizing.

CONCLUSIONS: Different mechanisms underlie early and late ScT: although incomplete BRS deployment was a predictor of the former, the latter was associated with large vessel size and BRS undersizing. However, both phenomena are significantly less frequent with an optimized implantation technique. (Mainz Intracoronary Database. The Coronary Slow-flow and Microvascular Diseases Registry [MICAT]; NCT02180178).