What to Do About Late Incomplete Stent Apposition?

Acute and subacute stent thromboses have existed since the first stent implantation procedures. Initially recognized as a complication of brachytherapy, late stent thrombosis has become a public health issue only during the current era of drug-eluting stent (DES) implantation, as evidenced by the March 8, 2007, issue of the New England Journal of Medicine , which includes 5 articles, 2 perspectives, and 1 editorial discussing late DES complications.Article p 2426 During every phase of percutaneous coronary intervention, intravascular ultrasound (IVUS) has provided important insights into the mechanisms of success and reasons for failure. In this issue of Circulation , Cook et al1 continue this tradition by reporting the IVUS findings in 13 patients who developed stent thrombosis >1 year after DES implantation. They concluded, “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.”Incomplete stent apposition (ISA), synonymous with stent malapposition, is a lack of contact between stent struts and the underlying vessel wall not overlying a side branch. ISA can be quantified by measuring the number of malapposed struts; the arc subtended by the malapposed struts; the distance between the malapposed struts and the vessel wall; and the area, length, and volume of the gap between the stent and vessel wall. ISA must be differentiated from and not confused with stent underexpansion. Stent expansion is the minimum stent area by itself or compared with a predefined reference. Although this distinction may seem obvious, ISA and stent underexpansion are used interchangeably by purported experts. Although the collaborative work of Nakamura and associates2 demonstrated an unexpectedly high percentage of IVUS-detected stent underexpansion and incomplete apposition after angiographically successful bare metal stent (BMS) implantations, no study has linked acute or subacute stent …