Stable myocardial strain despite ventricular and atrial dilatation in patients with a single left ventricle after the Fontan procedure

Abstract Background Patients with single ventricle are at risk of ventricular dysfunction and failure. However, the long-term evolution of myocardial function in patients with a single left ventricle (SLV) following completion of the Fontan circulation is not well understood, particularly with regard to ventricular and atrial deformation parameters. Objectives To assess longitudinal changes in volumetric and strain-based functional parameters in SLV patients following completion of the Fontan circulation using cardiovascular magnetic resonance imaging (CMR). Methods This retrospective study included 44 patients with SLV and Fontan physiology who underwent at least two serial CMR examinations over a median follow-up of 8 years. Volumetric and myocardial strain parameters were assessed using dedicated software. TAssessed variables included left ventricular (LVEDV, LVESV, LVSV, LVEF, and indexed volumes) and left atrial volumes and function (LAEDV, LAESV, LASV, LAEF, and indexed volumes), as well as LV global longitudinal strain (LV-GLS) and peak atrial longitudinal strain (PALS). Results A significant increase was observed in indexed left ventricular end-diastolic volume (LVEDVi), from a median of 74.5 ml/m² (IQR 69.4 ml/m² – 94.5 ml/m²) to 94.5 ml/m² (IQR 85.5 ml/m² –109.9 ml/m²; p = 0.0001), and in indexed left atrial end-diastolic volume (LAEDVi), from a median of 24,5 ml/m² (IQR 19,9 4 ml/m² – 30,4 ml/m²) to 27,2 ml/m² (IQR 21,6 ml/m² – 32,8 ml/m² ; p 0.0001). Despite these volumetric changes, LVEF remained stable at a median of ~53% (IQR 48.1%–59.5% at first scan vs. 48.1%–56.4% at follow-up; p = 0.5), and LAEF also showed no significant change (18.2%, IQR 12.6%–23.8% vs. 21.7%, IQR 15.3%–28.5%; p = 0.08). Strain parameters remained also unchanged: LV-GLS: –17.1% (IQR –20.4% to –12.6%) vs. –19.1% (IQR –21.1% to –13.9%); p = 0.87, PALS: 11.4% (IQR 8.0%–17.1%) vs. 10.3% (IQR 7,2 to 16,1%); p = 0.65 Despite low absolute strain values compared to healthy controls, no further decline was observed. A significant positive correlation was found between age at Fontan completion and indexed LA volume at follow-up (Spearman’s ρ = 0.337, p = 0.026), suggesting a link between surgical timing and atrial remodeling. Conclusion Despite progressive structural remodeling, functional deformation parameters remained preserved, indicating sustained compensatory capacity in this high-risk cohort. CMR-based strain analysis may be a valuable tool for non-invasive long-term monitoring and early risk stratification in Fontan patients with SLV.