Serum Proteomic Profiling Implicates a Dysregulated Neurohormonal-Inflammatory Axis in Post-Fontan Tachycardia

BackgroundPost-operative tachycardia is a common and poorly understood complication following the Fontan procedure. Post-operative factors such as surgical scarring and venous hypertension can contribute to tachycardia risk, but the specific molecular signaling cascades triggering acute tachycardia remain uncharacterized, limiting therapeutic innovation and leaving clinicians with only reactive management strategies. Here, we present a retrospective translational study leveraging serum proteomics and machine learning to identify the molecular drivers of post-operative Fontan tachycardia. MethodsWe integrated a clinically relevant ovine animal model of the Fontan circulation with continuous telemetric heart rate monitoring and human patient data. Serum proteomics coupled with machine learning algorithms (LASSO and Boruta) were employed to identify protein panels predictive of post-operative tachycardia. Cross-species validation was performed by comparing proteomic signatures from sheep and pediatric patients undergoing Glenn or Fontan surgery. ResultsOvine Fontan animals demonstrated significant heart rate elevation beginning on post-operative day (POD) 1, peaking at POD 3 (159.4 {+/-} 11.7 bpm vs. pre-operative 105.3 {+/-} 10.5 bpm, p<0.0001), before trending toward baseline by POD 10. This pattern was mirrored in human pediatric patients, though with a more modest magnitude. Surgical controls did not exhibit tachycardia, indicating the response was specific to the Fontan procedure. Proteomic analysis identified distinct separation between pre- and post-operative serum profiles. Principal component analysis revealed that the principal components most correlated with heart rate (PC1: r=0.79, p=6.5x10-; PC8: r=0.40, p=0.04) were significantly enriched for inflammatory and neural pathways. We leveraged the Boruta algorithm to identify a seven-protein panel (ACE, ANGT, ITIH4, SELENOP, W5PHP7, PTX3, and F5) with superior predictive power (AUC=0.926). A cross-species comparison between human and sheep demonstrated that three proteins, angiotensinogen (ANGT), angiotensin-converting enzyme (ACE), and pentraxin 3 (PTX3), were similarly dysregulated in both species post-operatively. ConclusionsThis study provides the first direct molecular evidence implicating a dysregulated neurohormonal-inflammatory axis as a principal driver of acute post-operative Fontan tachycardia. The identified protein signature offers novel mechanistic insights and establishes a foundation for developing targeted diagnostics and therapeutics to predict and mitigate this significant clinical complication.