Abstract Body (Do not enter title and authors here): Background: After TOF repair (TOFr), pulmonary regurgitation resulting in right ventricular (RV) dilatation and dysfunction is common. We have previously demonstrated that RV function (RVF) improves in the first two years after TOFr, however RV changes in the first decade after TOFr are less known. We investigated RVF and RV size (termed remodeling) using echocardiography during the first decade after TOFr.

Methods: Retrospective cohort study of patients who underwent TOFr and were followed at our institution from 3/2012 to 12/2023. Those with at least two echocardiograms separated by one year were included. Two patients that received a pulmonary valve replacement were excluded. After confirming intra- and inter-reader reproducibility, RV remodeling was assessed offline by global longitudinal strain (GLS), free wall strain (FWS), fractional area change (FAC), end systolic area (ESA/BSA) and end diastolic area (EDA/BSA). RVF changes over time were assessed with multivariable linear mixed effects models adjusting for perioperative covariates. Two years after TOFr (Y2) was used as reference given RVF peaks at this point following surgery.

Results: Out of 758 echocardiograms from 116 patients, 688 were suitable for analysis. Median age at TOFr was 3.5 months (IQR:1.92, 4.89). Compared to Y2, we identified the largest decline in RVF at Year 3, with no worsening from year to year until Y10. There were no associations of perioperative covariates with RVF except for ventriculotomy (FAC) and residual pulmonary stenosis (FWS). There was no progression in RV remodeling over the first decade after TOFr. (Graph, table).

Conclusion: After the initial 2-year improvement following TOFr, RVF worsens but remains stable throughout the first decade with stable RV size accounting for BSA. Our findings augment the knowledge of RV remodeling during childhood and could help guide outpatient follow up, counseling, frequency of echocardiograms, and timing of the first cardiac MR.