Background —The pathomechanisms underlying very late stent thrombosis (VLST) after implantation of drug-eluting stents (DES) are incompletely understood. Using optical coherence tomography (OCT), we investigated potential causes of this adverse event. Methods and Results —Between August 2010 and December 2014, 64 patients were investigated at the time-point of VLST as part of an international OCT registry. OCT pullbacks were performed after restoration of flow and analyzed at 0.4mm. A total of 38 early- and 20 newer-generation DES were suitable for analysis. VLST occurred at a median time of 4.7 years (IQR 3.1 to 7.5). An underlying ...