OBJECTIVES We sought to characterize the hemodynamic impact of mild coronary artery disease (CAD) using quantitative flow ratio (QFR, an angiography-derived fractional flow reserve [FFR]) in a population of patients with only non-significant CAD at baseline that subsequently experienced a myocardial infarction (MI). BACKGROUND The discriminatory value of FFR in patients with mild CAD remains imperfect. METHODS We retrospectively included patients who underwent invasive coronary angiography for an MI, in whom another angiogram had been performed within the previous 5 years. Three-dimensional quantitative coronary angiography, QFR, and lesion length analysis were conducted on lesions responsible for the MI (future culprit lesions, [FCL]) as well as on control lesions (non-culprit lesions, [NCL]). RESULTS Eighty-three FCL and 117 NCL were analyzed in 83 patients: FCL were more severe (median % diameter of stenosis [DS] 39.1% [29.8; 45.7] vs. 29.8% [25.0; 37.2], p