Differential impact of lipid levels on the association between homocysteine and new-onset atrial fibrillation in acute myocardial infarction patients.

BACKGROUND: Homocysteine (Hcy) and dyslipidemia are both established risk factors for cardiovascular disease. However, their interaction in the development of new-onset atrial fibrillation (NOAF) after acute myocardial infarction (AMI)-especially across different baseline LDL-C levels-is not well-understood. METHODS: This retrospective cohort study included 3,257 AMI patients. Within both normal lipid and dyslipidemia groups, participants were stratified by Hcy tertiles. Spearman correlation analysis was employed to examine the relationship between Hcy and lipid profiles. Multivariable logistic regression and generalized additive models with smooth curve fitting were utilized to investigate the association between Hcy levels and NOAF across varying baseline LDL-C profiles. Sensitivity and subgroup analyses confirmed the robustness of the findings. RESULTS: Analysis of 3,257 AMI patients revealed significant lipid-dependent associations between Hcy levels and the risk of in-hospital NOAF. Specifically, in patients with normal lipid levels, elevated Hcy was an independent risk factor for NOAF: each 1 µmol/L increase in Hcy conferred a 3.1% higher risk (fully adjusted odds ratio [OR] 1.031, 95% confidence interval [CI] 1.019-1.043; P < 0.001). A similar significant trend (P for trend < 0.05) was observed when Hcy was categorized. Notably, a linear relationship between Hcy levels and NOAF risk was evident in the normal lipid group. In contrast, among patients with dyslipidemia, neither unadjusted nor fully adjusted models demonstrated a significant association between Hcy levels and NOAF risk (all P > 0.05). Furthermore, the smooth curve analysis indicated that within the dyslipidemia group, the relationship between Hcy and NOAF risk approximated a horizontal line, consistent with the logistic regression model. Sensitivity and subgroup analyses confirmed the robustness of the findings. CONCLUSIONS: This study reveals that baseline lipid levels may modify the association between Hcy and NOAF in patients with AMI. Specifically, Hcy was associated with an increased risk of in-hospital NOAF in AMI patients with normal lipid profiles, whereas this association was not observed in those with dyslipidemia.