Antonius A.C.M. Heestermans

BACKGROUND: Stent thrombosis (ST) is a rare but serious complication following percutaneous coronary intervention. Analysis of thrombus composition from patients undergoing catheter thrombectomy may provide important insights into the pathological processes leading to thrombus formation. We performed a large-scale multicentre study to evaluate thrombus specimens in patients with ST across Europe. METHODS: Patients presenting with ST and undergoing thrombus aspiration were eligible for inclusion. Thrombus collection was performed according to a standardized protocol and specimens were analysed histologically at a core laboratory. Serial tissue cross sections were stained with haematoxylin-eosin (H&E), Carstairs and Luna. Immunohistochemistry was performed to identify leukocyte subsets, prothrombotic neutrophil extracellular traps (NETs), erythrocytes, platelets, and fibrinogen. RESULTS: Overall 253 thrombus specimens were analysed; 79 (31.2%) from patients presenting with early ST, 174 (68.8%) from late ST; 79 (31.2%) were from bare metal stents, 166 (65.6%) from drug-eluting stents, 8 (3.2%) were from stents of unknown type. Thrombus specimens displayed heterogeneous morphology with platelet-rich thrombus and fibrin/fibrinogen fragments most abundant; mean platelet coverage was 57% of thrombus area. Leukocyte infiltrations were hallmarks of both early and late ST (early: 2260 ± 1550 per mm(2) vs. late: 2485 ± 1778 per mm(2); P = 0.44); neutrophils represented the most prominent subset (early: 1364 ± 923 per mm(2) vs. late: 1428 ± 1023 per mm(2); P = 0.81). Leukocyte counts were significantly higher compared with a control group of patients with thrombus aspiration in spontaneous myocardial infarction. Neutrophil extracellular traps were observed in 23% of samples. Eosinophils were present in all stent types, with higher numbers in patients with late ST in sirolimus-and everolimus-eluting stents. CONCLUSION: In a large-scale study of histological thrombus analysis from patients presenting with ST, thrombus specimens displayed heterogeneous morphology. Recruitment of leukocytes, particularly neutrophils, appears to be a hallmark of ST. The presence of NETs supports their pathophysiological relevance. Eosinophil recruitment suggests an allergic component to the process of ST.

BACKGROUND: There are limited data on the long-term clinical outcome after an angiographically confirmed (definite) stent thrombosis (ST). METHODS AND RESULTS: Four hundred thirty-one consecutive patients with a definite ST were enrolled in this multicenter registry. The primary end point was the composite of cardiac death and definite recurrent ST. Secondary end points were all-cause death, cardiac death, definite recurrent ST, definite and probable recurrent ST, any myocardial infarction, and any target-vessel revascularization. The primary end point occurred in 111 patients after a median follow-up of 27.1 months. The estimated cumulative event rates at 30 days and 1, 2, and 3 years were 18.0%, 23.6%, 25.2%, and 27.9%, respectively. The cumulative incidence rates of definite recurrent ST, definite or probable recurrent ST, any myocardial infarction, and any target-vessel revascularization were 18.8%, 20.1%, 21.3%, and 32.0%, respectively, at the longest available follow-up. Independent predictors for the primary end point were diabetes mellitus, total stent length, severe calcification, American College of Cardiology/American Heart Association B2-C lesions, TIMI (Thrombolysis In Myocardial Infarction) flow grade <3 after percutaneous coronary intervention, and left ventricular ejection fraction <45%. The implantation of an additional coronary stent during the first ST was also associated with unfavorable outcome. Clinical outcome was not affected by the type of previously implanted stent (drug-eluting or bare-metal stent) or the category of ST (early versus late). CONCLUSIONS: The long-term clinical outcome after a first definite ST is unfavorable, with a high mortality and recurrence rate. Diabetes mellitus, left ventricular ejection fraction <45%, long total stent length, complex coronary lesions, TIMI flow grade <3 after percutaneous coronary intervention, and implantation of an additional coronary stent during the emergent percutaneous coronary intervention for the ST were associated with this unfavorable outcome.