Introduction: Tetralogy of Fallot (ToF) is a congenital heart disease requiring surgical correction in early childhood. Despite high surgical success rates, patients face severe morbidity during adulthood, primarily relating to the right ventricle (RV). Underlying pathophysiological processes remain largely unknown, but are commonly attributed to RV remodelling. Improved understanding of RV remodelling is essential for advancements in clinical decision making, requiring advanced monitoring techniques. Three-dimensional echocardiography (3DE) forms a promising option for the quantification of morphological and functional RV remodelling.
Aim: To identify global and regional differences in morphological and functional RV characteristics between ToF patients and healthy controls, using 3DE imaging. A software application will be developed to calculate global and regional mean curvature (MC) and directionally decomposed ejection fraction (dEF) to enhance understanding of RV remodelling in ToF patients.
Methods: Three-dimensional dynamic RV meshes were obtained from RV-focused 3DE studies of 50 ToF patients and 50 healthy controls, using commercially available software (TomTec 4D RV-Function). Regional morphological RV remodelling was assessed over nine regions using MC. Global and regional functional RV remodelling was evaluated over three regions using dEF in longitudinal (LT), radial (RD), and anteroposterior (AP) motion directions. A custom software application was developed for the calculation of both parameters, after which values were analysed and statistically compared within and between ToF patients and healthy controls. Correlations between dEF and left ventricular ejection fraction (LVEF) were investigated.
Results: RV remodelling was found to be a heterogeneous process, with different expressions throughout regions. Morphological RV remodelling was most evident in the posterior boundary, apex, and RV outflow tract regions, showing highly significant decreases of MC in ToF compared to healthy controls (p<0.001). Functional RV remodelling showed the most significant reduction of dEF in the AP motion direction in ToF patients compared to healthy controls (p<0.001), most evident in the anterior free wall region. The AP component of dEF was the only motion direction that did not show significant correlation with LVEF.
Conclusion: The posterior boundary, apex, and RV outflow tract regions showed largest decreases in curvature, making them highly interesting for further investigation. Deterioration of RV function was mostly assigned to decreased contribution of the AP wall motion direction to dEF, which showed no significant correlation with LVEF. Therefore, deterioration of the AP component of dEF was identified as a distinct feature of RV remodelling, making it an interesting candidate for advanced assessment of functional RV remodelling in ToF patients. Future research in ToF patients should focus on longitudinal follow-up, allowing for the identification of regions with significant remodelling over time. With the development of the software application, morphological and functional RV remodelling in any patient population can be investigated.