METHODS AND RESULTS - In the Harmonizing Outcomes with Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) study, a formal substudy included poststent and 13-month follow-up IVUS at 36 centers. Twelve patients with baseline IVUS who had definite/probable early ST ≤30 days after enrollment were compared with 389 patients without early ST. Significant residual stenosis was a lumen area <4.0 mm(2) with ≥70% plaque burden ≤10 mm from each stent edge. Significant edge dissection was more than medial dissection with lumen area <4 mm(2) or dissection angle ≥60°. Randomization to bivalirudin (P=0.29) or paclitaxel-eluting stent (P=0.74) was not related to early ST. Minimum lumen area was smaller in patients with versus without early ST (4.4 mm(2) [3.6, 6.9] versus 6.7 mm(2) [5.3, 8.0], respectively, P=0.014). Minimum lumen area <5 mm(2), significant residual stenosis, significant stent edge dissection, and significant tissue (plaque/thrombus) protrusion (more than the median that narrowed the lumen to <4 mm(2)) were more prevalent in patients with early ST, but significant acute malapposition (more than the median) was not. Overall, 100% of patients with early ST had at least 1 of these significant features: minimum lumen area <5 mm(2), edge dissection, residual stenosis, or tissue protrusion versus 23% in patients without early ST (P<0.01).

CONCLUSIONS - Smaller final lumen area and inflow/outflow disease (residual stenosis or dissection) but not acute malapposition were related to early ST after acute myocardial infarction intervention.

CLINICAL TRIAL REGISTRATION - URL: http://www.clinicaltrials.gov. Unique identifier: NCT00433966.