Abstract 6016: Pathology Of Hypersensitivity In Late Drug Eluting Stent Thrombosis
Background: Localized hypersensitivity (HS) has been reported as a pathologic risk factor for late DES thrombosis (DES-LST). The objectives of the study were to examine the pathologic features of HS in DES-LST and correlate with stent characteristics, underlying plaque morphologies and patient risk factors.
Materials and methods: From a registry of 153 DES patients, 33 patients with DES-LST were identified. LST was defined as platelet-rich thrombus in a coronary stent implanted > 30 days. Stented arteries were serially sectioned at 2–3 mm intervals and stained with H&E, Movat stain, Luna stain (eosinophils), and UCHL (T-lymphocytes). Localized HS was defined as an inflammatory cell infiltrate composed predominantly of eosinophils and T-lymphocytes limited to the arterial wall surrounding the stent. Patient data, risk factors, stent characteristics, and underlying plaque morphology were compared between two groups: hypersensitivity (HS), and non-hypersensitivity LST (NHS).
Results: Of the 33 DES-LST cases with occlusive thrombus, 6 (4 men, 2 women) demonstrated HS histologically (18%). The mean age was 54 years (range 40 – 62 years). All 6 had Cypher stents (mean stent length=24 mm), 4 had >1 stent, 2 with overlapping stents. The mean stent duration was 624 days (range 112 to 990 days). Three patients were on ASA and clopidogrel, 2 ASA only, 1 discontinued ASA/clopidogrel prior to non-cardiac surgery. Patient risk factors included hyperlipidemia (n=6), hypertension (n=5) and smoking (n=4). All demonstrated underlying fibroatheroma with stent struts penetrating necrotic core in 3 and 2 with previous rupture sites. Stent malapposition was present in 5 (83%). Twenty-seven patients demonstrated NHS-LST (Cypher=7, Taxus=20). Mean stent duration was 326 days (range 31–1200 days). Malapposition was identified in 10 (37%). Compared to NHS, the HS LST group was more likely to demonstrate stent malapposition (p=0.04) and longer implant times (p=0.049).
Conclusions: DES-LST is related to HS in 18% of cases, is associated with Cypher stents, malapposition and longer implantation time. Localized HS with stent thrombosis is a clinically important problem that may occur late after stenting and warrants further pathologic study.