Plasma Lipidomic Alterations in Fontan Circulation Reflect Cardiovascular Functional Reserve

Background: Fontan circulation is associated with impaired cardiac output, reduced exercise capacity, and systemic metabolic stress. However, the underlying lipidomic alterations remain poorly defined. Methods: Using targeted mass spectrometry, we analyzed 291 lipid species in fasting plasma samples from 20 adults with Fontan circulation and 20 age- and sex-matched healthy controls. Results: Forty-eight lipids were significantly altered between groups (p < 0.05), including reductions in total lysophosphatidylcholines (LPC) and total ether-linked LPC [LPC(O)] and elevations in total phosphatidylserines (PS). Notably, LPC(O-22:1) and LPC(O-20:0) were decreased, while PS 40:5 was elevated, with several of these species demonstrating strong correlations (|r| > 0.5, p < 0.001) with the stroke index, cardiac index, and VO₂max. These three lipid species also showed excellent capability in discriminating Fontan patients from healthy controls (AUC > 0.78). Correlation network and pathway enrichment analyses revealed tightly coordinated lipid clusters containing LPC/LPC(O), PE, and PS species as central features of dysregulated Fontan metabolism. Conclusions: These exploratory findings highlight coordinated lipid alterations associated with impaired cardiovascular reserve in Fontan patients. While based on unadjusted p-values and therefore being hypothesis-generating, they provide novel insight into the metabolic landscape of Fontan physiology and warrant validation in larger, independent cohorts.