Abstract 4606: Vascular Responses and Differential Mechanisms of Late Stent Thrombosis Following Sirolimus- and Paclitaxel- Eluting Stents in Humans
Background Clinical trials have reported differences in late lumen loss between sirolimus-(SES) and paclitaxel-(PES) drug-eluting stents (DES). However, differences in the vascular response, time course of healing, and mechanisms of late stent thrombosis (LST) between SES and PES remain unknown.
Methods From CVPath autopsy registry, 174 cases (230 DES lesions) were analyzed. Morphometric analysis was performed in 127 cases (171 lesions) who died ≥30days after stenting. Morphometric and histologic findings such as fibrin deposition, endothelial strut coverage, inflammatory response, and mechanisms of thrombosis were recorded.
Results The frequency of LST was similar between SES and PES (21% vs. 27%, p=0.47). However, the underlying mechanism was significantly different as localized hypersensitivity reaction was exclusively observed in SES while LST with malapposition and excessive fibrin deposition was only seen in PES. Neointimal thickness was greater in PES (0.13mm[0.03–0.20]) than SES (0.10mm[0.04–0.15], p=0.04), and both DES without stent thrombosis were associated with an increase in neointimal thickness over time (Figure⇓). While both DES showed near complete strut coverage after 12months for “on-label” usage, the majority of stents placed for “off-label” indications remained unhealed beyond 12months in both DES (Figure⇓).
Conclusion In this autopsy study, the mechanisms of LST were significantly different between SES and PES. Furthermore, DES placed for “on-label” indications demonstrated near complete healing after 12months, whereas DES placed for “off-label” indications remained unhealed.