Tricuspid Valve Adaptation during the First Interstage Period in Hypoplastic Left Heart Syndrome

Background: Tricuspid regurgitation (TR) is an important risk factor for morbidity and mortality in hypoplastic left heart syndrome (HLHS), yet the evolution of tricuspid valve (TV) dysfunction in HLHS is poorly understood. This study sought to examine changes in TV function in HLHS between the first two stages of surgical palliation and to determine the mechanism of TR at the time of stage two surgery—bidirectional cavopulmonary anastomosis (BCPA). Methods: We prospectively investigated 44 infants at two time points—prior to Norwood-Sano (T1 - median age 5.4 days) and prior to BCPA (T2 - median age 4.7 months) using two-dimensional (2DE) and three-dimensional echocardiography (3DE). Right ventricular (RV) size, function and shape was assessed with 2DE. Extracted spatial coordinates from 3DE were used to calculate TV leaflet and annular area, tethering and prolapse volumes, bending angle, and coaptation index. TR was graded qualitatively, and 2D and 3D vena contracta (VC) were measured. Results: The cohort from T1 to T2 had increased indexed leaflet and annular area (P <.0001) and tethering volume (P <.0001), with no change in coaptation. Significant TR was present in 14 infants (32%) at T2 and was associated with greater leaflet (P =.02) and annular areas (P =.002) and greater prolapse volume (P =.008), but not tethering volume or reduced coaptation. At latest follow-up (median 23 months), 13 patients died or required transplantation. Only 3DE VC at T2 was associated with death or transplantation. Conclusions: The TV in HLHS adapts to interstage stressors (increased preload and afterload) by increasing leaflet size to maintain adequate leaflet coaptation. Significant TR at T2 was associated with greater leaflet size and prolapse. This may represent TV maladaptation from an excessive response in leaflet expansion to stressors.