Volumetric Intravascular Ultrasound Analysis of Paclitaxel-Eluting and Bare Metal Stents in Acute Myocardial Infarction

Abstract

Background— Vascular responses to drug-eluting stents in ST-segment elevation myocardial infarction are unknown. In the prospective, multicenter Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) trial, patients with ST-segment elevation myocardial infarction within 12 hours of symptom onset were randomized 3:1 to TAXUS EXPRESS paclitaxel-eluting stents (PES) or EXPRESS bare metal stents (BMS). Methods and Results— A formal intravascular ultrasound substudy enrolled 464 patients with baseline and 13-month follow-up imaging at 36 centers. Overall, 446 lesions in 402 patients were suitable for standard qualitative and quantitative analyses, which were performed at an independent blinded core laboratory. The primary prespecified end point was the in-stent percent net volume obstruction at follow-up. Median stent length measured 23.4 mm (first and third quartiles, 18.5 and 31.9 mm). PES compared with BMS significantly reduced 13-month percent net volume obstruction (6.5% [first and third quartiles, 2.2% and 10.8%] versus 15.6% [first and third quartiles, 7.2% and 28.8%]; P <0.0001). PES compared with BMS also resulted in more late-acquired stent malapposition (29.6% versus 7.9%; P =0.0005) resulting from positive vessel remodeling. Plaque and/or thrombus protrusion through stent struts was initially present in 70.4% of PES and 64.8% of BMS; all resolved during follow-up. New aneurysm formation, stent fracture, and subclinical thrombus were uncommon, although seen only in PES. Conclusions— PES compared with BMS significantly reduce neointimal hyperplasia in patients with ST-segment elevation myocardial infarction but also result in a high frequency of late-acquired stent malapposition as a result of positive vessel remodeling. Ongoing long-term follow-up is required to establish the clinical significance of these findings. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00433966.