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

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 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. 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

Higher efficacy of pre-hospital tirofiban with longer pre-treatment time to primary PCI: protection for the negative impact of time delay

Item does not contain fulltextAIMS: To evaluate the impact of longer duration of pre-hospital initiated antiplatelet and antithrombotic therapy on outcome in patients with ST-segment elevation myocardial infarction (STEMI). METHODS AND RESULTS: In this sub-analysis of the Ongoing Tirofiban in Myocardial Evaluation (On-TIME) 2 trial, we studied, in 1,370 patients, the effect of pre-treatment time (time from administering study medication to time of angiography) on complete ST-segment resolution (STR), initial patency and 30-day mortality. Study medication consisted of high dose tirofiban (HDT) or control (placebo or no HDT) on top of high dose clopidogrel, aspirin and unfractionated heparin. Median pre-treatment time was 55 min (44-70). Longer pre-treatment was associated with longer transportation times, longer in-hospital delay, longer total ischaemic time (all p<0.001) and higher 30-day mortality (3.6% vs. 1.8%, p=0.046). Longer HDT pre-treatment time was independently associated with increased complete STR both before (odds ratio [OR] 1.51, 95%; confidence interval [CI] 0.98-2.32; p=0.06) and after PCI (OR 1.43, 95%; CI 1.02-2.02; p=0.039) and with a significantly improved initial TIMI 2 or 3 flow (51.4% vs. 43.4%, p=0.042) and reduced 30-day mortality (2.1% vs. 5.0%, p=0.047) as compared to longer control pre-treatment. CONCLUSIONS: Longer time delay before primary PCI is associated with increased mortality. Pre-treatment with high dose tirofiban, however, may compensate for this negative effect by improving ST-segment resolution and initial patency and by reducing mortality. Further studies should be performed to confirm that this is an attractive therapy for patients with longer delays to reperfusion