The ATI score (age-thrombus burden-index of microcirculatory resistance) determined during primary percutaneous coronary intervention predicts final infarct size in patients with ST-elevation myocardial infarction: a cardiac magnetic resonance validation study

Aims: The age-thrombus burden-index of microcirculatory resistance (ATI) score is a diagnostic tool able to predict suboptimal myocardial reperfusion before stenting, in patients with ST-elevation myocardial infarction (STEMI). We aimed to validate the ATI score against cardiac magnetic resonance imaging (cMRI). Methods and results: The ATI score was calculated prospectively in 80 STEMI patients. cMRI was performed within 48 hours in all patients and in 50 patients at six-month follow-up to assess the extent of infarct size (IS%) and microvascular obstruction (MVO%). The ATI score was calculated using age (>50=1 point), pre-stenting index of microcirculatory resistance (IMR) (> 40 and < 100=1 point; >= 100=2 points) and angiographic thrombus score (4=1 point; 5=3 points). ATI score was closely related to final IS% (ATI(0-1) : 16.5% [8.7-22.9], ATI(2-3) : 28.5% [15.5-35.0], ATI(4-5-6) : 35.5% [22.2-44.4], p=0.001) and with MVO% (ATI(0-1) : 0.0% [0.0-0.9], ATI(2-3) : 0.7% [0.0-2.5] and ATI(4-5-6) : 4.1% [1.2-10.7], p<0.001). Furthermore, ATI score predicted final IS% at six-month follow-up (ATI(0-1) : 12.7% [4.1-18.0], ATI(2-3) : 16.30% [8.0-24.7], ATI 4-5-6 : 29.5% [19.9-49.5], p=0.02). Conclusions: The ATI score performed prior to stenting in patients with STEMI can predict the likelihood of MVO% and IS% both acutely and at six-month follow-up cMRI.