Contraction Patterns of Post-Fontan Single Right Ventricle versus Normal Left and Right Ventricles in Children: Insights from Principal Strain Analysis

Background: Principal strain analysis (PSA) quantifies three-dimensional (3D) myocardial deformation using 3D speckle tracking echocardiography. It defines both amplitude and direction of the principal myocardial contraction, expressed as principal strain (PS), and a perpendicular secondary strain (SS) of lower intensity. We aim to apply PSA to describe the contractile pattern in the single right ventricle (SRV) functioning as a systemic chamber in hypoplastic left heart syndrome (HLHS), compared with normal left ventricle (LV) and right ventricle (RV), and to compare SRV function with conventional echocardiographic evaluations. Methods: Sixty-four post-Fontan HLHS patients and age-matched controls (LV: 64, RV: 48) underwent computation of PS-lines, ejection fraction (EF), end-diastolic volume indexed by body surface area (EDVi), PS, SS, circumferential strain (CS), and longitudinal strain (LS). The PS-lines were compared between groups. Linear regressions with coefficient determination (R2) of strains, fractional area change (FAC), and tricuspid annular plane excursion with EF and EDVi were assessed in SRV. Additionally, HLHS cohort was equally divided into two groups, higher and lower EF groups, followed by comparison of all parameters. Results: The pattern of PS-lines demonstrated a left-handed direction in anterior free wall, a right-handed direction in posterior free wall, and a circumferential direction in medial wall in SRV. In contrast, in the normal LV the principal contraction is in the circumferential direction whereas in the normal RV it is predominantly longitudinal. R2 of PS, SS, and CS on EF were high (0.88, 0.72, and 0.90, respectively), whereas R2 of LS was comparable with FAC (0.56 and 0.55). All parameters were independent of EDVi. PS-lines of higher EF group showed a more circumferential orientation than lower EF group in SRV. Conclusions: PSA provides a unique functional map of SRV contraction. This map differs from corresponding maps of normal LV and RV. This may be helpful in understanding the mechanisms of SRV function, although future longitudinal studies are needed.