Histopathological evaluation of thrombus in patients presenting with stent thrombosis. A multicenter European study: a report of the prevention of late stent thrombosis by an interdisciplinary global European effort consortium

Abstract

BackgroundStent 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.MethodsPatients 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.ResultsOverall 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 mm2 vs. late: 2485 ± 1778 per mm2; P = 0.44); neutrophils represented the most prominent subset (early: 1364 ± 923 per mm2 vs. late: 1428 ± 1023 per mm2; 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.ConclusionIn 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.

The role of leukocytes in thrombosis

“…113,114 Histologic analysis of coronary artery and catheter-associated arterial thrombi demonstrated the presence of monocytes, neutrophils, and eosinophils within the thrombi. 115,116 Although murine models do not typically display spontaneous atherothrombosis, intravital models of arterial thrombosis address thrombus formation in macrovascular beds in the context of activated or damaged endothelium. Vessel wall TF is unequivocally involved in thrombus initiation in arterial thrombosis, 117 however, the role of circulating leukocyte or leukocyte-derived TF regulating arterial thrombus formation is less clear.…”

Demystifying the prothrombotic role of NETs

“…In fact, NETs are present in arterial thrombi of patients with myocardial infarction and in thrombus specimens retrieved from the venous circulation. 5 Inhibition of NET formation or dismantling NETs by DNase treatment reduces thrombosis in mice. 6,7 Thus, targeting NETs has evolved as an interesting strategy for the treatment of thrombotic conditions.…”

Propagation of thrombosis by neutrophils and extracellular nucleosome networks

“…6 In addition, neutrophils are by far the most important innate leukocyte subtype in stent thrombosis. 54 Apart from neutrophils, eosinophils were present in all types of stent thrombosis, indicating a highly sensitive determinant that could induce thrombosis via eosinophil-associated TF.…”

“…The importance of these findings is underscored by the detection of NET in association with neutrophils in specimens of human coronary thrombi ( Figure 1) and at lesion sites of patients with acute myocardial infarction and stent thrombosis. 6,53,54 NET could only be detected in early stages of coronary thrombosis, but not in organized thrombi, which could be attributed to digestion of NET by plasma DNases or disruption of NET by heparin treatment applied during cardiac catheterization. 53 Increased NET burden in coronary thrombi correlated with infarct size, and DNase treatment (in particular together with tissue plasminogen activator) promoted resolution of coronary thrombi ex vivo, suggesting that a combination of established antithrombotic and NET-disrupting therapy might be beneficial in the therapy of acute coronary syndromes.…”