In vivo virtual histology intravascular ultrasound comparison of neointimal hyperplasia within drug-eluting- versus bare metal stents.

Background: The process of in-stent neointimal hyperplasia (NIH) between drug-eluting stents (DES) and bare metal stents (BMS) might be different. We compared in vivo composition of in-stent NIH between DES and BMS using virtual histology-intravascular ultrasound (VH-IVUS).
Methods and Results: Volumetric VH-IVUS was used to compare in-stent NIH between 23 DES and 15 BMS in 30 patients who underwent coronary angiography because of angina. The inner and outer VH-IVUS contours were drawn in a way to avoid the stent strut artifacts. Cross-sectional analysis was done at every VH-IVUS frame within the stent, thereby allowing volumetric measurement of stent, lumen, and NIH and its components. Baseline characteristics and IVUS measurements were similar between DES and BMS groups. The duration of follow-up was similar between DES (median 38 months [interquartile range, 7-59]) vs. BMS (median 40 months [interquartile range, 7-99]), (p=0.26). % necrotic core (NC) volume was significantly higher in DES than BMS: 19.5 [16.3, 25.6] vs. 12.1 [8.2, 18.5] (p=0.006). %NC volume significantly increased with time in BMS (p=0.007), but not in DES (p=0.24) so that at any given time point, %NC in DES was greater than in BMS. After adjustment for baseline differences, only DES (p=0.003) and stent age (p=0.043) were independent predictors of %NC volume. VH-IVUS in-stent thin-cap fibroatheromas were detected only in the DES group: 34.8% vs. 0%, p=0.013.
Conclusion: In vivo composition of in-stent NIH between DES and BMS was different, suggesting that the process of in-stent NIH in DES and BMS is diverse.