PCI Complications: Restenosis

Editors-In-Chief: Alexandra Almonacid M.D. and Jeffrey J. Popma M.D.

Restenosis Pattern
In the setting of in-stent restenosis (ISR) after bare metal stent (BMS) implantation, the risk of recurrence can be predicted by the pattern of restenosis (1, 2).

Classification System
'''Table 1. Mehran Classification System (1)'''


 * Pattern I:  Focal (≤ 10 mm in length) lesions
 * Ia : Restenosis within the stent
 * Ib : Restenosis at the edge of the stent
 * Ic : Restenosis at the articulation or gap
 * Id : Restenosis multifocal
 * Pattern II: ISR >10 mm within the stent
 * Pattern III: Includes ISR > 10 mm extending outside the stent
 * Pattern IV: ISR totally occluded

Implications
The need for recurrent target lesion revascularization (TLR) increased with increasing ISR class, increasing from 19%, 35%, 50%, to 83% in classes I to IV, respectively (P <0.001) (1). Restenosis after drug eluting stent implantation is generally more focal than following bare metal stent placement (3, 4), and, with the sirolimus-eluting stent, more is commonly at the margin of the stent due to balloon injury that is not covered with stent (3, 5).


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