Incomplete stent apposition and very late stent thrombosis after drug-eluting stent implantation

Background - Stent thrombosis may occur late after drug-eluting stent (DES) implantation, and its cause remains unknown. The present study investigated differences of the stented segment between patients with and without very late stent thrombosis with the use of intravascular ultrasound. Methods and Results - Since January 2004, patients presenting with very late stent thrombosis (> 1 year) after DES implantation underwent intravascular ultrasound. Findings in patients with very late stent thrombosis were compared with intravascular ultrasound routinely obtained 8 months after DES implantation in 144 control patients, who did not experience stent thrombosis for >= 2 years. Very late stent thrombosis was encountered in 13 patients at a mean of 630 +/- 166 days after DES implantation. Compared with DES controls, patients with very late stent thrombosis had longer lesions (23.9 +/- 16.0 versus 13.3 +/- 7.9 mm; P < 0.001) and stents (34.6 +/- 22.4 versus 18.6 +/- 9.5 mm; P < 0.001), more stents per lesion (1.6 +/- 0.9 versus 1.1 +/- 0.4; P < 0.001), and stent overlap (39% versus 8%; P < 0.001). Vessel cross-sectional area was similar for the reference segment (cross-sectional area of the external elastic membrane: 18.9 +/- 6.9 versus 20.4 +/- 7.2 mm(2); P=0.46) but significantly larger for the in-stent segment (28.6 +/- 11.9 versus 20.1 +/- 6.7 mm(2); P=0.03) in very late stent thrombosis patients compared with DES controls. Incomplete stent apposition was more frequent (77% versus 12%; P < 0.001) and maximal incomplete stent apposition area was larger (8.3 +/- 7.5 versus 4.0 +/- 3.8 mm(2); P=0.03) in patients with very late stent thrombosis compared with controls. Conclusions - Incomplete stent apposition is highly prevalent in patients with very late stent thrombosis after DES implantation, suggesting a role in the pathogenesis of this adverse event.