Incidence of stent under-deployment as a cause of in-stent restenosis in long stents

Although stent under-deployment (SU) has been associated with increased risk of in-stent restenosis, little data have been reported on the incidence of SU in patients presenting with clinical in-stent restenosis. In 59 patients referred for vascular brachytherapy and showing angiographic in-stent restenosis, we sought ( 1) to determine the incidence of SU using standard intravascular ultrasound (IVUS) criteria ( 2) to evaluate the effects of repeat angioplasty on further stent expansion. Stented length was 32 +/- 17 mm and diameter stenosis was 75 +/- 14%. Before re-intervention, the incidence of reduced absolute values of minimal stent cross-sectional area (MSCSA) varied from 69% ( less than or equal to 8 mm(2)) to 15% (less than or equal to5 mm(2)). After re-intervention, the incidence decreased to 24% (less than or equal to8 mm(2)) ( p = 0.0001) and 0% (less than or equal to5 mm(2)) ( p = 0.005). Before re-intervention, SU as assessed by relative criteria varied from 21% ( 80% mean reference lumen area or 90% minimum distal reference lumen area) to 28% (100% minimum reference lumen area). After re-intervention, the incidence of SU varied from 7% ( 90% minimum distal reference lumen area) ( p = 0.0001 vs. pre) to 24% (55% mean reference EEM area) ( p = ns). No change in strut apposition (97% pre vs. 100% post) nor in symmetry index ( 100% pre vs. post) was noted. From all criteria, the 90 and 100% minimum reference lumen area criteria were the most altered by repeat balloon dilatation, 21% pre vs. 7% post and 28% pre vs. 11% post, respectively. In conclusion, among patients presenting with severe angiographic in-stent restenosis, a significant number showed signs of SU whose incidence varied according to applied criteria. Significant stent re-expansion can be obtained following IVUS-guided repeat angioplasty irrespective of initial SU criteria.