Follistatin and Systolic Function at Follow-Up in STEMI Patients: A Cardiac Magnetic Resonance Study.

Background/Objectives: Early circulating biomarkers capable of identifying patients at risk for impaired recovery of left ventricular (LV) systolic function after ST-segment elevation myocardial infarction (STEMI) remain limited. This exploratory study aims to determine whether serum follistatin measured within the first 24 h after coronary revascularization is associated with long-term LV systolic function, as assessed by cardiac magnetic resonance (CMR). Methods: In this prospective study, 31 patients with reperfused STEMI underwent serial CMR at 1 week and 6 months. Follistatin levels were measured within 24 h after revascularization. Associations between follistatin and CMR-derived LV systolic function were assessed using univariate and multivariable linear regression analyses. Results: Patients were stratified by median follistatin level (438 pg/mL) into below median (n = 15) and above median (n = 16). At 1 week, CMR-derived LV function, volumes, and structural indices were similar between groups. By 6 months, however, patients with follistatin above the median had higher LV ejection fraction (LVEF) [62 ± 9% vs. 54 ± 9%; p-value = 0.018] and lower LV end-systolic volume index (28 ± 12 vs. 41 ± 18 mL/m2; p-value = 0.037). In univariate analysis, follistatin was associated with 6-month LVEF (β = 0.027 per pg/mL; p-value = 0.004). After multivariable adjustment, follistatin remained independently associated with 6-month LVEF (β = 0.024 per pg/mL; p-value < 0.001) and with relative improvement in LVEF from 1 week to 6 months (β = 0.044 per pg/mL; p-value < 0.001). Conclusions: In reperfused STEMI patients, higher early follistatin levels were independently associated with more favorable LV systolic function at 6 months. These hypothesis-generating findings suggest that follistatin may represent a potential biomarker of subsequent systolic recovery after STEMI, warranting further validation in larger prospective studies.