Table 2.

SCAI classification of in-stent restenosis: a system based on time interval and causative factor

Classification	Time interval	Morphologic substrates
Early	<30 d	•Undersizing •Underexpansion •Stent fracture
Late	30 d to 1 y	•Delayed healing (including drug induced) •Uncovered stent struts •Intimal hyperplasia (especially in BMS ISR)
Very late	>1 y	•Neoatherosclerosis •Intimal hyperplasia •Stent fracture

BMS, bare metal stent; ISR, in-stent restenosis.