Resistance to platelet antiaggregants: an important cause of very late thrombosis of drug eluting stents? Observations from five cases Résistance aux anti-agrégants plaquettaires : cause importante de thrombose très tardive de stent actif ? À propos de cinq observations

Summary Background. — Very late thrombosis of drug eluting stents is a rare complication that might betriggered by resistance to platelet antiaggregants (PAAs). Aim . — Following an initial case where clinical data strongly suggested resistance to PAAs, wecarried out a prospective systematic analysis of platelet aggregation in four subsequent casesof late thrombosis. Methods. — Resistance to aspirin was investigated with the PFA-100 test employing a collagen-epinephrine cartridge (Platelet Function Analyzer; Dade Behring). Resistance to clopidogrelwas determined by flow cytometry of intraplatelet vasodilator-stimulated phosphoprotein(VASP) phosphorylation. Results. — All four cases showed resistance to either aspirin or clopidogrel, and two casesshowed dual resistance to both of these PAAs. Conclusion. — Analysis of platelet function in a patient with late stent thrombosis is useful andmay allow adaptation of subsequent patient management. The value of monitoring plateletfunction after implantation of a drug eluting stent should be evaluated in prospective studies. © 2008 Published by Elsevier Masson SAS.