Intravascular ultrasound assessment of minimum lumen area and intimal hyperplasia in in-stent restenosis after drug-eluting or bare-metal stent implantation. The Nordic Intravascular Ultrasound Study (NIVUS)

Introduction: Drug-eluting stents (DES) reduce the risk of restenosis after percutaneous coronary intervention. The aim of the study was to evaluate, by intravascular ultrasound (IVUS), the minimum lumen area site in the stented segment and the distribution of intimal hyperplasia in patients presenting with a DES or bare-metal stent (BMS) in-stent restenosis. Methods: The “Nordic Intravascular Ultrasound Study (NIVUS)” study was conducted in Nordic and Baltic countries as a prospective multicenter registry. Two hundred nine patients (DES n = 121 and BMS n = 88) with in-stent restenosis were enrolled. Results: At the minimum lumen area site in the stented segment, the stent area (5.8 ± 2.2 mm² vs. 7.6 ± 2.4 mm², p < 0.001) and intimal hyperplasia area (2.6 ± 2.0 mm² vs. 5.0 ± 2.2 mm², p < 0.001) were significantly lower in patients treated with DES compared to BMS. The percentage of stents that did not have a minimum stent area of at least 5.0 mm² (under expansion) was higher in DES (58.7% vs. 37.7%, p = 0.008) compared to BMS. Intimal hyperplasia covered 55.4 ± 33.3% of the stent length in the DES compared to 90.7 ± 17.4% in the BMS group, p < 0.001. Focal in-stent restenosis was more often seen in DES treated patients compared to BMS treated patients (DES n = 84 (59.9%) vs. BMS n = 15 (17.0%), p < 0.001). Conclusion: Stent underexpansion was more often seen in DES than BMS in-stent restenosis. DES more often had focal in-stent restenosis with less intimal hyperplasia.