Impact of Large Thrombus Burden on Very Long-Term Clinical Outcomes in Patients Presenting With ST-Segment Elevation Myocardial Infarction.

Abstract

The impact of large thrombus burden (LTB) on very long-term clinical outcomes in patients with ST-segment elevation myocardial infarction (STEMI) is unknown. We compared very long-term clinical outcomes in STEMI patients with either LTB or small thrombus burden (STB). Between 2002 and 2004, thrombus burden (TB) was evaluated in consecutive patients with STEMI undergoing percutaneous coronary intervention (PCI). In occluded infarct-related arteries, TB was reclassified after flow restoration. LTB was defined as thrombus ≥2 vessel diameters. Major adverse cardiac event (MACE) rate was evaluated at 10-year follow-up and survival data were collected up to 15 years post PCI. A total of 812 patients were enrolled, and TB assessment was available for 806 patients (99.3%); 580 patients (72.0%) had STB and 226 patients (28.0%) had LTB. Patients with LTB experienced more no reflow (4.0% vs 0.5%; P<.01) and distal embolization (17.3% vs 3.4%; P<.001) than STB patients. Ten-year MACE rate (42.5% vs 42.4%; P=.59), 10-year mortality rate (27.0% vs 26.4%; P=.75), and 15-year mortality rate (31.9% vs 35.9%; P=.29) were similar between STB and LTB groups, respectively. By landmark analysis, MACE rate was higher in the LTB group (15.9% vs 8.8%; P<.01) at 30 days, but not beyond (31.6% vs 36.9%; P=.28). There was no difference in mortality at any time point (at 30 days, 9.7% vs 6.2%; P=.08; beyond 30 days, 17.3% vs 20.5%; P=.48). LTB was an independent predictor of MACE at 30 days post PCI (hazard ratio, 1.60; 95% confidence interval, 1.01-2.51; P=.04). In STEMI patients, LTB might identify a subpopulation at high risk of no-reflow, distal embolization, and early ischemic events, but is not associated with worse clinical outcomes at long-term follow-up.