Aortic Haemodynamics Are Independent Longitudinal Determinants of Left Ventricular Function in Repaired Tetralogy of Fallot

BACKGROUND: Left ventricular ejection fraction (LVEF) independently predicts mortality in repaired tetralogy of Fallot (ToF), but the causes of LV dysfunction are incompletely understood. The intrinsic aortopathy of ToF increases pulsatile afterload, yet whether this contributes to LV dysfunction is unknown. We sought to determine whether aortic dimensions and flow-derived afterload act as cross-sectional markers of LV dysfunction, dynamic contributors to change in LV function over time, or both. METHODS: Retrospective longitudinal study of 554 patients with repaired ToF (1,448 serial cardiovascular magnetic resonance examinations, 2003-2026). Aortic root dimensions, total arterial compliance (TAC: aortic forward flow volume/pulse pressure), and systemic vascular resistance (SVR) were derived, and a within-between decomposition separated between-patient from within-patient associations with LVEF in mixed-effects models. RESULTS: In the analytic sample (1,053 observations, 521 patients), aortic sinus diameter predicted LVEF at both levels (within:{beta} = -0.23, p<0.001; between: {beta} = -0.20, p=0.003). Associations were reproduced at the sinotubular junction but absent at the ascending aorta, localising the effect to the root. TAC predicted LVEF within patients ({beta}=0.90 per mL/mmHg, p=0.014) but not between patients (p=0.62), indicating that pulsatile afterload is a dynamic contributor to LV function. SVR predicted LVEF at both levels (within: {beta} = -0.23; between: {beta} = -0.25; both p<0.001). Blood pressure components alone, expressed as systolic and diastolic or as mean arterial and pulse pressure, did not predict LVEF and fitted the data less well. Adjustment for right ventricular ejection fraction attenuated the within-patient compliance association by 35%, suggesting a component shared with right ventricular function. CONCLUSIONS: Aortic root dimensions, TAC and SVR are independent longitudinal determinants of LVEF in repaired ToF, establishing an important role for aortic haemodynamics in LV function and identifying the systemic vasculature as a potentially modifiable contributor to LV dysfunction.