Intravascular Ultrasound Findings of Early Stent Thrombosis After Primary Percutaneous Intervention in Acute Myocardial Infarction A Harmonizing Outcomes With Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) Substudy

Background-Small stent area and residual inflow/outflow disease have been reported as the strongest intravascular ultrasound (IVUS) predictors of early stent thrombosis (ST) in patients with stable angina. IVUS predictors of early ST in patients with acute myocardial infarction have not been studied. 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 degrees. 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.