A pilot investigation of the tricuspid valve annulus in newborns with hypoplastic left heart syndrome.

Objective: Hypoplastic left heart syndrome (HLHS) is a congenital disease characterized by an underdevelopment of the anatomical components inside the left heart. Approximately 30% of HLHS newborns will develop tricuspid regurgitation (TR), and it is currently unknown how the valve annulus mechanics and geometry are associated with regurgitation. Thus, we present an engineering mechanics-based analysis approach to quantify the mechanics and geometry of the HLHS-afflicted tricuspid valve (TV), using 4-dimensional echocardiograms.

Methods: Infants born with hypoplastic left heart syndrome (=8) and healthy newborns (=4) had their tricuspid valves imaged, and the data was imported to the 3D Slicer. The annular curves were defined at five points in the cardiac cycle. The geometry and deformation (strain) of the TV annulus were calculated to elucidate the mechanics of this critical structure, and compare them between HLHS and normal neonates.

Results: For the annular geometry, HLHS-afflicted newborns had significantly larger annular circumferences (20-30%) and anterior-posterior diameters (35-45%) than the healthy patients. From a biomechanics perspective, the HLHS patients had significantly smaller strains in the anterior segments (-0.1±2.6%) during end diastolic and end isovolumetric relaxation (1.7±3.0%) compared to the healthy counterparts (-13.3±2.9% and 6.8±0.9%, respectively).

Conclusions: The image-based analysis in this study may provide novel insights into the geometric and mechanistic differences in the TV annulus between healthy and HLHS newborns. Future longitudinal studies of the biomechanics of TV annulus and other subvalvular structures may inform our understanding of the initiation and development of TR and the design of optimal repairs in this challenging population.