BACKGROUND: Tricuspid valve regurgitation (TR) is associated with morbidity and mortality in hypoplastic left heart syndrome (HLHS). Over 25% of
HLHS patients require tricuspid valve (TV) repair within 10 years, while the mechanism of TR remains poorly understood. This study explores TV
remodeling in HLHS requiring surgical repair, using novel quantitative three-dimensional echocardiography (3DE) to further understand the
mechanisms of TV failure in HLHS.
METHODS AND RESULTS: This case-control study with prospectively acquired 3DE in 72 children with HLHS, 36 children prior to TV repair (group 1) and 36 age- and stage-matched controls with no TV repair and mild or less TR (group 2). All 3DE were analyzed using a specific custom TV software (MATLAB) to quantitate TV annulus and leaflet area (Figure), prolapse and tethering volumes, and bending angle. TV leaflets were segmented into the anterior (AL), septal (SL) and posterior (PL) to measure regional areas and volumes. We also measured position of papillary muscle (PM) and chord length. Variables were indexed by body surface area (BSA), and comparison was performed using t-test with significance at p < 0.05. Group 1 and 2 had similar age and BSA (mean: 2.3 years; 0.47 m2) at assessment. Group 1 had larger total annulus (10.3 vs 8.4 cm2/m2, P< 0.001) and leaflet (11.7 vs 9.3 cm2/m2, P= 0.002) area. SL area (2.66 vs. 2.00 cm2/m2, p= 0.009) was larger and AL trended to being larger (5.2 vs 4.2 cm2/m2, P= 0.05). Group 1 had larger total prolapse volume and for each leaflets (Total leaflet 140 vs 5.8 μl/m2, p=<0.002; AL: 39.4 vs 2.2 μl/m2, p= 0.004; SL: 2.2 vs 0.16 μl/m2, p= 0.017; PL: 2.7 vs 0.12 μl/m2, p= 0.032). No difference in tethering volume for total or each leaflet. Group 1 had greater bending angle (156.6 vs 151.8 degree, p= 0.034), hence a flatter annulus. No difference in PM angle and length, nor chord length between the groups.
CONCLUSION: Failing TV in children with HLHS had larger annulus and leaflet size, specifically in SL and AL, and greater prolapse of all the leaflets compared to HLHS with competent TV. Despite increased leaflet prolapse, there is no difference in chord or PM length, suggesting that failing TV prolapse is due to leaflet mal-adaptation, rather than chord or PM changes. This novel insight suggests future research into TV leaflet mal/adaptation in HLHS maybe important.