OBJECTIVES - The aim of this study was to determine the prognostic value of fractional flow reserve (FFR) in non-infarct-related arteries (IRAs) in ST-segment elevation myocardial infarction (MI).

BACKGROUND - Patients with ST-segment elevation MI often present with multivessel disease. The treatment of non-IRAs is debated. The applicability of FFR has not been widely proved.

METHODS - Outcomes were analyzed in all patients in the Compare-Acute (Comparison Between FFR Guided Revascularization Versus Conventional Strategy in Acute STEMI Patients With MVD) trial in whom, after successful primary percutaneous coronary intervention, non-IRAs were interrogated using FFR and treated medically. The treating cardiologist was blinded to the FFR value. The primary endpoint was the composite of cardiovascular mortality, target vessel–related (non-IRA with FFR measurement at primary percutaneous coronary intervention) nonfatal MI, and target vessel revascularization: major adverse cardiac events (MACE) at 24 months.

RESULTS -  A total of 751 patients (963 vessels) were included. Target non-IRAs with MACE had lower FFR compared with those without (0.78 vs. 0.84, respectively; p < 0.001). The median FFR of non-IRAs with TVR was lower than that of those without (0.79 vs. 0.85, respectively; p < 0.001). The difference was significant in all vessels. The median FFR of target non-IRAs with MI was lower than that of those without (0.79 vs. 0.84, respectively; p = 0.016). The MACE rate was significantly (p < 0.001) higher in the lowest of FFR tertiles (<0.80) compared with the others (0.80 to 0.87 and ≥0.88).

CONCLUSIONS - In patients with ST-segment elevation MI with multivessel disease, FFR measured in the medically treated non-IRA immediately after successful primary percutaneous coronary intervention shows a nonlinear and inverse risk continuum of MACE. Importantly, worsening prognosis is demonstrated around the cutoff of 0.80.