Presence of older thrombus in patients with late and very late drug-eluting stent thrombosis

Summary Background Although drug-eluting stents (DES) have considerably reduced the incidence of in-stent restenosis, late and very late stent thrombosis (ST) after DES implantation have emerged as major safety concerns. We morphologically investigated the age of DES thrombi aspirated during percutaneous coronary intervention (PCI) from patients with either late or very late ST that resulted in acute myocardial infarction (AMI). Methods and results We obtained DES thrombi during PCI from 16 consecutive patients with ST (late and very late ST, n  = 4 and n  = 12, respectively), who presented with AMI within 24 h of the onset of anginal symptoms. Thrombi were morphologically classified as fresh, lytic, and organized. Fresh thrombus was identified in 5 (31%) of the 16 patients and lytic thrombus was found in 3 (19%). Organized thrombus was notably found in 8 (50%) patients, of whom 5 (31%) had only the organized type and 3 (19%) had both fresh and organized thrombi. The frequency of fresh thrombus tended to be higher in patients with stent failure such as stent malapposition and fracture, but the difference did not reach significance ( p  = 0.06). Conclusions Although the study group is small, about two-thirds of DES thrombi in late and very late ST were days or weeks old. These findings suggest an important discrepancy between the time of onset of the intra-stent thrombotic process and the occurrence of acute clinical symptoms, and provide further information about another potential mechanism of DES thrombosis.