The contribution of "mechanical" problems to in-stent restenosis: An intravascular ultrasonographic analysis of 1090 consecutive in-stent restenosis lesions

Objectives Serial intravascular ultrasonographic (IVUS) studies have shown that in-stent restenosis is the result of intimal hyperplasia (IH). However, routine preintervention IVUS imaging has suggested that many restenotic stents were inadequately deployed. The purpose of this IVUS study was to determine the incidence of mechanical problems contributing to in-stent restenosis (ISR). Methods Between April 1994 and June 2000, 1090 patients with ISR were treated at the Washington Hospital Center. All underwent preintervention IVUS imaging. IVUS measurements included proximal and distal reference lumen areas and diameters; stent, minimum lumen, and IH (stent minus lumen) areas; and IH burden (IH/stent area). Results In 49 ISR lesions (4.5%), there were morphologic findings that contributed to the restenosis. These were termed mechanical complications. Examples include (1) missing the lesion (eg, an aorto-ostial stenosis), (2) stent "crush," and (3) having the stent stripped off the balloon during the implantation procedure. Excluding mechanical complications, stent under-expansion was common. In 20% of the ISR cases the stents had a cross-sectional area (CSA) at the site of the lesion <80% of the average reference lumen area. Twenty percent of lesions had a minimum stent area <5.0 mm(2) and an additional 18% had a minimum stent area of 5.0 to 6.0 mm(2). Twenty-four percent of lesions had an IH burden <60%. Conclusion Mechanical problems related to stent deployment procedures contribute to a significant minority of ISR lesions (approximately 25%).