The J-Curve Relationship between Free Carnitine Levels and Cardiovascular Events in Patients with Heart Failure

Hypocarnitinemia is thought to exacerbate heart failure by impairing mitochondrial function and increasing oxidative stress. While some studies suggest that elevated acylcarnitine levels are linked to cardiovascular events, limited data are available on the relationship between free carnitine levels and clinical outcomes in heart failure patients. This study aimed to investigate the association between free carnitine levels and clinical outcomes in patients hospitalized for heart failure. This retrospective study included 271 consecutive patients admitted to our hospital for their first episode of acute heart failure. Patients were divided into four quartiles based on free carnitine levels (quartile 1: <37.0 μmol/L, n=69; quartile 2: 37.0-49.7 μmol/L, n=68; quartile 3: 49.7-58.9 μmol/L, n=67; quartile 4: ≥58.9 μmol/L, n=67). The primary endpoints were 1-y cardiac mortality, rehospitalization due to heart failure, and its composite endpoint. The incidence of cardiovascular events was compared among the quartiles. Creatinine levels were significantly higher in quartile 4 than in other groups. There were no significant differences in age or BNP among the four groups. Additionally, the 1-y mortality rate was significantly higher in both quartile 1 and quartile 4, while the rehospitalization rate for heart failure within 1 y post-discharge was significantly higher in quartile 4. In summary, the relationship between free carnitine levels and mortality in heart failure patients showed a J-curve pattern, with both low and high levels associated with worse outcomes. Thus, extreme free carnitine levels may serve as potential risk factors for adverse clinical outcomes in this population.