Abstract 18520: Impaired Ubiquitin-Proteasome Function in Right Ventricular Myocardium Correlates to Postoperative Outcomes in Tetralogy of Fallot

Introduction: At the time of initial repair, patients with Tetralogy of Fallot (TOF) undergo a sudden shift from a pressure to volume loaded right ventricle (RV). It is difficult to predict how TOF RVs will respond to this hemodynamic transition. Identifying mechanisms and targets may enable interventions to improve outcomes.

Hypothesis: RV myocardial gene expression profiles at the time of TOF repair correlate to pre- and early postoperative clinical outcomes.

Methods: RNAseq was performed from RV myocardium resected at the time of initial TOF repair (n=44). Gene expression profiling was performed using a weighted gene correlation network analysis (WGCNA) against pre- and post-op clinical variables. Mouse pulmonary artery band (PAB, n=9) stratified by degree of RV dilation was used to correlate pathways.

Results: WGCNA identified a gene module that was associated with younger age at repair and worse TOF postop outcomes (prolonged milrinone, decreased right atrial and right ventricular strain) without a concomitant association with preop oxygen saturation. Biological process gene-set enrichment analysis using the 2023 Gene Ontology library revealed enrichment of regulators for ubiquitination, cell cycle/mitosis, DNA repair, microtubule polymerization, and Rho/GTPase. PAB mouse RV demonstrated a RV-dilation severity-dependent increase in bound ubiquitin (R ² =0.61, p=0.01) and loss of free ubiquitin (R ² =0.72, p=0.004; Figure).

Conclusions: WGCNA reveals a RV myocardial gene expression profile that is associated with preoperative characteristics and early postoperative outcomes, and which is enriched for ubiquitination regulators. The PAB mouse recapitulates a severity-dependent increase in bound ubiquitin and loss of free ubiquitin which is consistent with literature suggesting proteostatic dysfunction and accumulation of misfolded proteins in RVF. Targeting proteostatic disruption prior to TOF repair may improve postoperative outcomes.