Intravascular ultrasound findings in patients with very late stent thrombosis after either drug-eluting or bare-metal stent implantation.

OBJECTIVES This study compared intravascular ultrasound (IVUS) findings at drug-eluting stent (DES) and bare-metal stent (BMS) sites in patients with very late stent thrombosis (VLST). BACKGROUND VLST is being increasingly identified since the introduction of DES. VLST can also develop after BMS placement, but the underlying mechanisms remain unknown. METHODS A total of 30 consecutive VLST patients with acute myocardial infarction (DES, n = 23; BMS, n = 7) were enrolled. Patients underwent IVUS examination before coronary angioplasty. RESULTS The baseline characteristics were similar for the 2 groups, with the exception of reference vessel size, lesion length, stent length, minimal lumen diameter, and diameter stenosis after the procedure. Overall, VLST occurred at a mean 50.8 +/- 36.2 months after the index procedure, and occurred earlier after DES than BMS (33.2 +/- 12.5 months vs. 108.4 +/- 26.5 months, p < 0.001). IVUS variables were generally similar for the 2 groups. However, plaque burden at the distal reference segment, stent, and neointimal area of the in-stent segment were smaller in the DES group. Stent malapposition was observed in 73.9% of DES patients, but in no BMS patients (p = 0.001). Disease progression with neointimal rupture within the stent was observed in 10 DES patients (43.5%) and 7 BMS patients (100%; p = 0.010). CONCLUSIONS Stent malapposition was unique to DES-related VLST, whereas disease progression with neointimal rupture was more common in BMS patients. These findings suggest that different biological mechanisms underlie VLST development depending upon the stent type.