ObjectiveTo explore the association between free fatty acid (FFA) and extent of severity of acute coronary syndrome (ACS). MethodsWe analyzed the clinical data of 93 ACS in-patients treated between July 2014 and May 2015, including 35 with acute ST-elevation myocardial infarction (STEMI), 34 with acute non STEMI (NSTEMI), and 24 with unstable angina (UA). Another 29 in-patients during the same period without coronary heart disease and heart failure and with normal results of electrocardiogram and myocardial damage markers were selected as the control. The statistical analysis of FFA collected within 24 hours after admission was conducted. ResultsThe FFA in the ACS group[(1.08±0.41) mmol/L] was significantly higher than that in control group[(0.51±0.15) mmol/L] (P < 0.01). The FFA in patients with STEMI, NSTEMI, and UA in ACS group was (1.32±0.38), (1.12±0.35, and (0.67±0.10) mmol/L, respectively; the FFA in STEMI and NSTEMI patients was much higher than that in the UA patients (P < 0.05), and the difference between STEMI and NSTEMI patients was not significant (P > 0.05). There were 58 NSTEMI and UA patients evaluated by Grace risk score, in whom 30 had Grace score≥140 with the FFA of (1.12±0.37) mmol/L and 28 had < 140 with the FFA of (0.73±0.17) mmol/L; the difference was significant (P < 0.05). There were 35 STEMI patients evaluated by Killip grade, in whom 16 were Killip I-II with the FFA of (1.17±0.37) mmol/L, and 19 were Killip III-IV with the FFA of (1.45±0.35) mmol/L; the difference was significant (P < 0.05). ConclusionElevated plasma FFA could be associated with ischemic risk and extent of severity of ACS.