Fractional Flow Reserve and Instantaneous Wave-Free Ratio for Nonculprit Stenosis in Patients With Acute Myocardial Infarction

The aim of this study was to compare the changes of fractional flow reserve (FFR) or instantaneous wave-free ratio (iFR) with severity of epicardial coronary stenosis between nonculprit vessel of acute myocardial infarction (AMI) and stable ischemic heart disease (SIHD).There has been debate regarding the reliability of FFR or iFR for nonculprit stenosis in the acute stage of AMI.A total of 100 AMI patients underwent comprehensive physiologic assessment including FFR, iFR, coronary flow reserve (CFR), and index of microcirculatory resistance (IMR) for nonculprit vessel stenosis after primary percutaneous coronary intervention (PCI) for culprit vessel. The changes in FFR and iFR for diameter stenosis (%DS) of nonculprit vessel stenosis were compared with FFR and iFR measured in 203 patients with SIHD.From 40% to 80% stenosis, FFR and iFR measured in nonculprit vessel of AMI patient showed significant decrease with worsening stenosis severity (all p values 0.001). Nonculprit vessels of AMI patients showed lower CFR than SIHD; however, IMR was not different between the nonculprit vessel of AMI and SIHD patients. FFR and iFR were not significantly different between the nonculprit vessel of AMI and SIHD patients in all %DS groups from 40% to 80% (all p values0.05). In addition, percent difference of FFR and iFR according to the increase in %DS was also not significantly different between nonculprit vessel of AMI or SIHD. There was no significant interaction between clinical presentation and the changes of FFR and iFR for worsening %DS (interaction p value = 0.698 and 0.257, respectively).Changes in FFR and iFR for the nonculprit stenosis of AMI patients were not significantly different from those in SIHD patients. These data support the use of invasive physiological parameters to guide treatment of nonculprit stenoses in the acute stage of successfully revascularized AMI.