Relationship between myocardial reperfusion, infarct size, and mortality: the INFUSE-AMI (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction) trial.

OBJECTIVES: This study sought to compare infarct size (IS) measured by magnetic resonance imaging in patients with successful (myocardial blush grade [MBG] 2/3) versus unsuccessful (MBG 0/1) microcirculatory reperfusion in the INFUSE-AMI (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction) trial.

BACKGROUND: Successful microcirculatory reperfusion, defined angiographically by MBG 2 or 3, is associated with improved outcomes in patients with ST-segment elevation myocardial infarction. The precise mechanism underlying this association is not well defined.

METHODS: The INFUSE-AMI trial randomized 452 patients with anterior ST-segment elevation myocardial infarction to intracoronary bolus abciximab delivered locally at the infarct lesion versus no abciximab, and to manual thrombus aspiration versus no aspiration. The primary endpoint was IS (percentage of left ventricular mass) at 30 days.

RESULTS: MBG 2/3 was achieved in 367 patients (81.4%). IS was significantly lower in patients with MBG 2/3 than in those with MBG 0/1 (median: 16.7% [interquartile range (IQR): 7.0 to 22.7] vs. 19.5% [IQR: 11.1 to 29.2]; p = 0.002). Intracoronary abciximab further reduced IS in patients with MBG 2/3 (median: 14.4% [IQR: 5.4 to 20.9] vs. 17.4% [IQR: 10.5 to 23.8]; p = 0.01). MBG 2/3 was associated with ∼30% reduction in infarct mass (p = 0.002) and ∼90% reduction in microvascular obstruction on day 5. Ejection fraction was higher with MBG 2/3 at 30 days: median: 50.3% (IQR: 43.8 to 57.8) versus 46.9% (IQR: 37.5 to 54.0); p = 0.004. At 30 days, the rate of death was significantly lower (1.7% vs. 8.3%; p = 0.0008) in the MBG 2/3 group.

CONCLUSIONS: MBG 2/3 occurs in 80% of ST-segment elevation myocardial infarction patients treated with primary percutaneous coronary intervention and is associated with smaller infarct size, less microvascular obstruction, improved ejection fraction, and significantly lower 30-day mortality. (Intracoronary Abciximab and Aspiration Thrombectomy in Patients With Large Anterior Myocardial Infarction [INFUSE-AMI]; NCT00976521).