Intravascular ultrasound assessment of drug-eluting stent expansion

Background: In the drug-eluting stent (DES) era, stent expansion remains an important predictor of restenosis and subacute thrombosis. Compliance charts are developed to predict final minimum stent diameter (MSD) and area (MSA). The objectives of the study were (1) to assess DES expansion by comparing intravascular ultrasound (IVUS)-measured MSD and MSA against the values predicted by compliance charts and (2) to compare each DES against its bare-metal stent (BMS) equivalent. Methods: We enrolled 200 patients with de novo coronary lesions treated with single, >2.5-mm Cypher (Cordis, Johnson & Johnson, Miami Lakes, FL) (sirolimus-eluting stent [SES], 133 patients) or Taxus (Boston Scientific, Natick, MA) (paclitaxel-eluting stent [PES], 67 patients) stent under IVUS guidance without another postdilation balloon. We used a comparison cohort of 65 equivalent BMS (Express 2 [Boston Scientific], 37 patients; Bx Velocity [Cordis, Johnson & Johnson], 28 patients) deployed under similar conditions. Results: The DES achieved only 75% ± 10% of predicted MSD and 66% ± 17% of predicted MSA; this was similar for SES and PES. Furthermore, 24% of SES and 28% of PES did not achieve a final MSA of 5 mm², a consistent predictor of DES failure. The SES achieved 75% ± 10% of predicted MSA versus 75% ± 9% for Bx Velocity (P = .9). The PES achieved 79.9% ± 14% of predicted MSA versus 79% ± 10% for Express 2 (P = .8). Lesion morphology, arc and length of calcium, stent diameter and length, and implantation pressures did not affect expansion. Conclusions: Compliance charts fail to predict final MSD and MSA. A considerable percentage of DES does not achieve minimum standards of stent expansion. The SES and PES achieve similar expansion to their BMS platform, indicating that the polymer coating does not affect DES expansion in vivo. However, stent expansion cannot be predicted from preintervention IVUS lesion assessment.