Association of Fibroblast Growth Factor 23 With Recurrent Cardiovascular Events in Patients After an Acute Coronary Syndrome: A Secondary Analysis of a Randomized Clinical Trial

Importance Elevated fibroblast growth factor 23 (FGF-23) concentrations are associated with myocardial fibrosis and renin-angiotensin system upregulation, potentially providing prognostic information distinct from standard cardiovascular (CV) biomarkers. Objective To evaluate the association of FGF-23 with recurrent CV events in patients after an acute coronary syndrome (ACS). Design, Setting, and Participants C-terminal FGF-23 was measured in plasma samples using an established enzyme-linked immunosorbent assay system for 4947 patients within 30 days of ACS (median, 14 days) and with 1 additional CV risk factor in the Stabilization of Plaques Using Darapladib-Thrombolysis in Myocardial Infarction 52 (SOLID-TIMI 52) trial of the lipoprotein-associated phospholipase A2 inhibitor darapladib vs placebo performed from December 1, 2009, to April 24, 2014 (median follow-up, 2.5 years). Analyses were adjusted for clinical risk factors, renal function, and established cardiorenal biomarkers. This secondary analysis was performed from September 25, 2014, to October 1, 2017. Exposure The FGF-23 concentration at baseline. Main Outcomes and Measures The primary end point for this post hoc analysis was the composite of CV death or hospitalization for heart failure. Results In this study, baseline FGF-23 concentrations were available for 4947 patients (median age, 64.0 years; interquartile range, 59.0-71.0 years; 1276 [25.8%] female). Patients with higher FGF-23 concentrations were older and more likely female, with a greater proportion of hypertension, diabetes, and previous myocardial infarction. After multivariable adjustment for baseline clinical characteristics and established biomarkers (high-sensitivity troponin I, brain-type natriuretic peptide, and high-sensitivity C-reactive protein), FGF-23 concentration in the top quartile was independently associated with an increased risk of CV death or heart failure hospitalization (adjusted hazard ratio [HR], 2.35; 95% CI, 1.82-3.02; P < .001) and its individual components. Elevated FGF-23 concentration was also associated with an increased risk of all-cause mortality (adjusted HR, 2.27; 95% CI, 1.73-2.97; P < .001) and CV death, myocardial infarction, or stroke (adjusted HR, 1.42; 95% CI, 1.17-1.71; P < .001). When analyses were stratified by patient sex, the association between FGF-23 and CV risk, including CV death or heart failure, appeared to be attenuated in women (adjusted HR, 1.11; 95% CI, 0.70-1.76; P = .67) compared with men (HR, 3.11; 95% CI, 2.29-4.22; P < .001; P < .001 for interaction). Conclusions and Relevance In patients stabilized after ACS, elevated FGF-23 concentrations may be associated with recurrent major CV events and all-cause mortality, providing information independent of established clinical risk factors and cardiorenal biomarkers. A potential sex difference in these findings deserves further study.