Mejía-Rentería H, et al. - Researchers determined if physiological evaluation of non-infarct-related arteries (non-IRA) during the subacute phase of myocardial infarction might be flawed by microcirculatory dysfunction. They assessed non-IRA that underwent fractional flow reserve, coronary flow reserve, and the index of microcirculatory resistance evaluation. In 49 acute myocardial infarction patients (59 non-IRA), they assessed microcirculation and hyperemic response, which were compared with 46 stable angina (SA) patients (59 vessels) constituting a matched control group. An increased baseline flow that could result in abnormal coronary flow reserve despite preserved hyperemic flow, was demonstrated by non-IRA in the subacute phase of myocardial infarction. Microcirculatory resistance and adenosine-induced hyperemic response in non-IRA were similar to those observed in SA patients. To examine non-IRA during the subacute phase of myocardial infarction, use of fractional flow reserve was supported from a physiological perspective.