Figure 2.

Types of stent induced injury. (A) Circumferential oversize plus large interstrut distances between 3 and 9 o'clock have led to stretch of the arterial wall and moderate circumferential neointima formation. There is one deep injury, where the strut at 4 o'clock has penetrated both the IEL and the EEL. Neointima formation is not confined to the area immediately around each strut. (B) A typical section with mild oversize, stretch, and neointima, despite similar interstrut distances to (A). (C) Mild oversize with more struts than (B), but similar neointima; the stent is therefore not a direct stimulus to neointima formation. (D) Almost no stretch or neointima, despite gross strut protrusion between 7 and 12 o'clock. Geometrical variations in the stent thus only lead to neointimal growth in the presence of stretch. (E) Despite a strut distribution similar to (D), the addition of mild stretch drives mild neointima formation. (F) Oversize (distal end of a stent) with destruction of both the internal and external elastic laminae; obvious deep injury rather than stretch. Neointimal growth is concentric and considerable. EEL, external elastic lamina; IEL, internal elastic lamina.