Potential difficulty for accurate categorization of drug-eluting stent thrombosis without coronary angiography: unignorable involvement of the cases with new onset acute myocardial infarction occurred in target vessels.

Very late stent thrombosis (VLST) is a major unresolved problem of drug-eluting stent (DES) implants. However, its actual incidence with respect to the distribution of DES-target vessel and accuracy of adjudicating stent thrombosis according to the ARC definition has not been yet adequately evaluated. We studied 720 patients who had completed over 1 year from elective DES implantation. In this cohort, we extracted patients who present acute coronary syndrome (ACS) (n = 3, 0.4%). The timing of ACS events was 17, 19, and 24 months after DES implantation. At the time of presentation, VLST was strongly suspected as the initial diagnosis, however, coronary angiography (CAG) confirmed the different culprit lesion from DES and clearly no thrombus within the DES. According to ARC definition, three probable stent thromboses in this cohort before CAG, however, no stent thrombosis was confirmed after the CAG. Thus, no stent thrombosis was confirmed among this study population. In the very late phase after DES implantation, new onset ACS is not at all extraordinary occurrence in the target vessels of previous DES implantation. However, stent thrombosis is often assumed without angiographic confirmation. The clinical possibility that non-stent thrombosis is incidentally diagnosed with stent thrombosis without angiographic confirmation should be considered within the current accepted definition of stent thrombosis.