Impact of ultra-thin struts on restenosis after chronic total occlusion recanalization: Insights from the randomized PRISON IV trial

Objectives: The PRISON-IV trial showed inferior outcome in patients with chronic total occlusions (CTOs) treated with the ultrathin-struts (60 μm for stent diameter ≤3 mm, 81μm >3 mm) hybrid-sirolimus eluting stents (SES) compared with everolimus eluting stents (EES, 81 μm). The aim of this study is to investigate if the use of smaller stents (≤3 mm) was responsible for the inferior outcome reported in the trial. Methods: In the PRISON-IV trial 330 patients with CTO lesion were randomized 1:1 to receive either hybrid-SES or EES. The hybrid-SES failed to reach the non-inferiority primary endpoint of in-segment late lumen loss (LLL) at 9-month angiographic follow-up. In this sub-analysis, we divided the population according to the different size of stents implanted in those receiving only stents with diameter ≤3 mm (Group-A, 178 patients), only stents >3 mm (Group-B, 59 patients), and those receiving stents of both sizes (Group-C, 93 patients). Results: Baseline and procedural characteristics were comparable in the three groups. At angiographic follow-up, most of the adverse outcomes occurred in Group A, with higher incidence of binary restenosis in the Hybrid-SES versus EES (10.3% vs 1.3%, P = 0.03) and augmented in-stent diameter stenosis (26.04 ± 18.59% vs 21.24 ± 12.84, P = 0.06). Similarly, optical coherence tomography (OCT), which was performed in 60 patients at follow-up, documented a mild trend toward lower values of minimum in stent area in Hybrid-SES arm of Group A (4.4 ± 1.02mm2 vs 5.0 ± 1.28mm2, respectively, P = 0.16). Conclusions: The present analysis suggests that the inferior performance of the ultra-thin hybrid-SES in CTO-PCI is particularly pronounced when smaller stent (≤3 mm diameter) are adopted, if compared with EES.