Figure 1: Heterogeneity of neointimal healing following drug-eluting stent placement. A 34-year-old woman underwent placement of one sirolimus-eluting stent (SES) (22 × 3 mm) stent in the proximal left circumflex artery for acute myocardial infarction 2 years antemortem. The patient was admitted to emergency room with ST-elevation myocardial infarction and subsequently expired. Consecutive sections of SES were cut 3 mm apart, stained with Movat Pentachrome (a), and measurements of neointimal thickness (above each strut) and the number of uncovered stent struts performed (b). There is greater neointimal growth above each strut (×) and fewer uncovered stent struts (red circle) within the proximal and distal stented portion, with absence of luminal thrombus formation. At the site of thrombus formation (Sections 5 and 6), neointimal thickness is minimal and the number of uncovered stent struts is maximal. (c), Movat Pentachrome-stained. Sections 5 and 7 show detailed histology. There is a platelet-rich thrombus surrounding stent struts lacking neointima (*) in Section 5. High power images (I, II) show uncovered stent struts with extensive underlying fibrin deposition (grey arrowhead), luminal platelet-rich thrombus (Thr), and lack of endothelialization (II, black arrowhead) following immunostaining for CD31/CD34. However, positive staining (brown) is observed within medial microvessels containing CD31/CD34-positive endothelial cells (white arrowhead). In contrast, there is a well-healed neointima with complete strut coverage in Section 7. High power images (III, IV) show stent struts embedded into neointima composed of smooth muscle cells and proteoglycans; there is an absence of luminal thrombus, and endothelial cells are abundant above stent struts (IV, white arrowhead) with positive staining (brown). (Reproduced with permission from [11].)