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

Objectives: 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).

Methods: 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.

Results: 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).

Conclusions: 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.