Mechanism of late in-stent restenosis after implantation of a paclitaxel derivate-eluting polymer stent system in...

Area of Science:

• Cardiovascular Research
• Biomaterials Science
• Histopathology

Background:

• Delayed restenosis was previously observed in patients treated with 7-hexanoyltaxol (QP2)-eluting polymer stents (QuaDS).
• This study investigates the histological characteristics of restenotic lesions in these patients.

Purpose of the Study:

• To determine the histological composition of restenotic lesions in patients treated with QuaDS-QP2 stents.
• To compare the healing patterns with those typically seen in coronary arteries.

Main Methods:

• Atherectomy specimens from 5 patients treated with QuaDS-QP2 stents were analyzed.
• Histological assessment included special stains, immunohistochemistry, and transmission electron microscopy.
• Proliferation index was evaluated using Ki-67 antibody staining.

Main Results:

• Restenotic lesions showed fibrin, smooth muscle cells, proteoglycans, and in some cases, macrophages and T-lymphocytes.
• Areas of inflammation exhibited a high proliferation index, while smooth muscle cell-rich areas had a low index.
• Findings suggest delayed healing with persistent inflammation at 12 months post-implantation.

Conclusions:

• QuaDS-QP2 stents exhibit delayed healing characterized by persistent fibrin and inflammation at 12 months.
• These pathological findings differ significantly from the typical 3-month healing observed with stainless steel stents.
• The non-absorbable polymer component of the stent may contribute to chronic inflammation.