Study Uses IVUS to Analyze Mechanisms of In-Stent Restenosis After DES Implantation

February 9, 2011—Results of an investigation using intravascular ultrasound (IVUS) to clarify the mechanisms of luminal loss after drug-eluting stent (DES) implantation and to classify morphological patterns of in-stent restenosis (ISR) were published by Soo-Jin Kang, MD, et al online ahead of print in Circulation: Cardiovascular Interventions.

On the basis of IVUS-identified luminal narrowing (in-stent minimum lumen area < 4 mm²), the investigators classified IVUS-defined ISR as focal (luminal narrowing ≤ 10 mm in length), multifocal (≥ 1 focal lesions), and diffuse (luminal narrowing > 10 mm in length) with or without stent edge involvement. Significant intimal hyperplasia (IH) was defined as IH area > 50% of stent. Overall, 76 lesions had IVUS-defined ISR; 32 (42%) had stent underexpansion (minimal stent area < 5 mm²); and 71 (93%) had IH area > 50% of stent.

As detailed in Circulation: Cardiovascular Interventions, the investigators reported that the total stent length negatively correlated with the minimal stent area (r = −0.613; P < .001) as well as with stent area at the minimum lumen site (r = −0.436; P < .001) but not with minimum lumen area (r = −0.084; P = .472). Underexpansion was present at the minimum lumen site in 15 of 43 (35%) lesions with stent length > 28 mm, even though there was significant IH in 34 (79%) lesions; conversely, in 32 of 33 (97%) lesions with stent length ≤ 28 mm, the minimum lumen site was not associated with stent underexpansion but significant IH. IVUS-defined focal ISR was most common (47%).

Compared with focal ISR, normalized vessel, stent, lumen, and plaque volumes were smaller in diffuse and multifocal ISR than in focal ISR, with no difference in IH extent. From these findings, the investigators concluded that IH was the dominant mechanism of ISR in most DES restenosis but that underexpansion associated with longer stent length remained an important preventable mechanism of ISR.