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.