Impact of post-dilatation on longitudinal stent elongation: An in vitro study

Objectives: To evaluate whether balloon inflation for post-dilatation causes longitudinal stent deformation (LSD). Methods and results: Two stents, sized 2.5 mm × 28 mm and 3.5 mm × 28 mm (Nobori ^® , biodegradable polymer biolimus-eluting stent; Ultimaster ^® , biodegradable polymer sirolimus-eluting stent; Terumo Co., Tokyo, Japan), were deployed at nominal pressure in straight and tapered silicon vessel models. Then, post-dilatation was performed in two ways: dilatation from the distal (D-P group) or proximal (P-D group) side of the stent. Microscopic findings showed that the stents were elongated during every step of the procedure regardless of the post-dilatation method and type of vessel model. The D-P group showed linear elongation during each step of post-dilatation (straight model: 28.7 ± 0.3 mm vs. 29.9 ± 0.3 mm, p = 0.002; tapered model: 28.0 ± 0.1 mm vs. 29.9 ± 0.1 mm, p < 0.001). In contrast, in the P-D group, the most significant change was observed in the first step of post-dilatation and only slight changes were observed thereafter (straight model: 28.6 ± 0.1 mm vs. 29.5 ± 0.1 mm, p < 0.001; tapered model: 28.2 ± 0.1 mm vs. 29.5 ± 0.1 mm, p < 0.001). Optical frequency domain imaging analysis showed that the frequency of stent strut malapposition was positively correlated with the percentage change in stent length (r = 0.74, p < 0.0001). Conclusion: LSD was observed during every step of post-dilatation in both the straight and tapered vessel models. However, some differences were observed between the D-P and P-D groups. Minimizing stent strut malapposition may reduce the risk of LSD.