Intravascular lithotripsy in drug-eluting stents: an ex-vivo analysis of structural integrity

Aims Intravascular lithotripsy (IVL) is currently indicated for calcium modification during lesion preparation prior to percutaneous coronary intervention. However, its off-label application in under-expanded stents is increasingly reported in the medical literature. The extent of stent architectural disruption caused by IVL in this context remains unclear. This study aims to employ electron microscopy (EM) to assess and quantify the physical effects of IVL on the structural integrity of various types of polymer-free and polymer-coated drug-eluting stents (DES). Methods Six different DES platforms were evaluated using a Phenom XL G2 Desktop Scanning Electron Microscope (SEM). 3.0mm stents were deployed and subjected to IVL treatment ex-vivo in a water bath maintained at 37°C. Eighteen SEM images were captured across 3 stents of each stent platform at baseline and after 20, 50, and 80 shocks using IVL catheters to assess architectural disruption. SEM scans were performed at low (250x) and high (1000x) magnification. Architectural disruption was quantified on SEM using a stent architectural deformation assessment (ADA) grade (1) defined as follows: Grade 0 – no damage; Grade I – presence of cracking, pitting, or blister formation without polymer or drug peeling; Grade II – partial-thickness peeling of polymer or drug; Grade III – full-thickness peeling of polymer or drug with visible underlying metal surface; Grade IV – visible disruption to the stent's metal architecture. The ADA grades from all 18 images for across the 3 stents of each stent platform were averaged to produce a Disruption Score for each stent platform at baseline, 20, 50 and 80 shocks. These were analysed via a two-way mixed-design ANOVA, with the stent platform (Polymer free Cre8, Onyx Resolute, Promus Elite, Synergy, Xience Sierra, Ultimaster) as the between-subjects factor and shock level (0, 20, 50, 80) as the within-subjects (repeated-measures) factor. A significance threshold of p < 0.05 was used for all comparisons. Post-hoc pairwise comparisons were conducted using Bonferroni-adjusted estimated marginal means Results All six DES platforms showed progressive damage with increasing IVL shocks. The mixed-design ANOVA indicated a significant main effect of shock level (p < 0.01), confirming that higher pulse counts led to greater disruption scores across all stent types. A significant main effect of brand (p < 0.01) revealed that the polymer-free Cre8 stent consistently exhibited lower Disruption Scores compared to the other polymer-coated stents. Conclusion IVL therapy induced stepwise stent architectural disruption with increasing shock pulses across all six DES platforms tested. The polymer-free Cre8 stent demonstrated the lowest disruption at each shock level, which may be a consideration when considering off-label IVL usage. There was no significant difference in disruption score amongst the other polymer-coated stent platforms.