Modeling of the Tricuspid Valve and Right Ventricle in Hypoplastic Left Heart Syndrome With a Fontan Circulation

Abstract

Background: In hypoplastic left heart syndrome, tricuspid regurgitation (TR) is associated with circulatory failure and death. We hypothesized that the tricuspid valve (TV) structure of patients with hypoplastic left heart syndrome with a Fontan circulation and moderate or greater TR differs from those with mild or less TR, and that right ventricle volume is associated with TV structure and dysfunction.

Methods: TV of 100 patients with hypoplastic left heart syndrome and a Fontan circulation were modeled using transthoracic 3-dimensional echocardiograms and custom software in SlicerHeart. Associations of TV structure to TR grade and right ventricle function and volume were investigated. Shape parameterization and analysis was used to calculate the mean shape of the TV leaflets, their principal modes of variation, and to characterize associations of TV leaflet shape to TR.

Results: In univariate modeling, patients with moderate or greater TR had larger TV annular diameters and area, greater annular distance between the anteroseptal commissure and anteroposterior commissure, greater leaflet billow volume, and more laterally directed anterior papillary muscle angles compared to valves with mild or less TR (all P<0.001). In multivariate modeling greater total billow volume, lower anterior papillary muscle angle, and greater distance between the anteroposterior commissure and anteroseptal commissure were associated with moderate or greater TR (P<0.001, C statistic=0.85). Larger right ventricle volumes were associated with moderate or greater TR (P<0.001). TV shape analysis revealed structural features associated with TR, but also highly heterogeneous TV leaflet structure.

Conclusions: Moderate or greater TR in patients with hypoplastic left heart syndrome with a Fontan circulation is associated with greater leaflet billow volume, a more laterally directed anterior papillary muscle angle, and greater annular distance between the anteroseptal commissure and anteroposterior commissure. However, there is significant heterogeneity of structure in the TV leaflets in regurgitant valves. Given this variability, an image-informed patient-specific approach to surgical planning may be needed to achieve optimal outcomes in this vulnerable and challenging population.

Keywords: Fontan procedure; heart ventricles; hypoplastic left heart syndrome; tricuspid valve; tricuspid valve insufficiency.

Figure 1.

Visualization of leaflet metrics. A, Anterior leaflet distance (anterior septal commissure [ASC] to anterior posterior commissure [APC]) along the annular curve. B, Tricuspid valve (TV) anterior leaflet area from the atrial view. C, Coaptation length (red), area (gray), and height (navy). D, Total leaflet billow volume. E, Total leaflet tenting volume; F, Papillary muscle angle (red) as measured between the plane of the annulus (navy) and the muscle chord. LV indicates left ventricle, and PSC, posterior septal commissure.

Figure 2.

Comparison of trivial regurgitation population mean shape and individual patient valves. A, Leaflet model of patient with significant billow and moderate or greater tricuspid regurgitation (TR); (B) Overlay of patient with billow leaflet model (red) on trivial population mean shape (gray); (C) Vector model displaying difference between billowing leaflet shape and mean shape of trivial TR population; (D) Leaflet model of patient with significant tenting and moderate or greater TR; (E) Overlay of patient with tenting leaflet model (blue) on trivial population mean shape (gray); (F) Vector model displaying difference between patient with tenting leaflet shape and mean shape of trivial TR population.

Figure 3.

Shape analysis of tricuspid valves by tricuspid regurgitation (TR) group. A, Trivial/mild TR mean population shape n=65 and moderate/severe population mean shape n=35; (B) Trivial population mean shape n=17 and severe population mean shape n=5; (C) Visual representation of the separating hyperplane (in red) created using distance-weighted discrimination that separates the valves into two regurgitant groups. Valves more distant from the hyperplane are statistically more likely to be in their assigned group using distance-weighted discrimination.

Figure 4.

Leaflet and annular metrics versus total annulus area; anterior papillary muscle angle versus ventricular volume. A-C, Leaflet area versus total annulus area (mid-systole [MS]). D, Comparison of slopes of leaflet area versus total annulus area (MS). E-G. Leaflet distance along annulus curve versus total annulus area (MS). H, Comparison of slopes of leaflet distance along annulus curve versus total annulus area (MS). I-J, Transformed global billow and tenting volume versus total annulus area (MS). K, Annular height versus total annulus area (MS). L, Transformed anterior papillary muscle (APM) angle (MS) versus ventricular volume (end-diastole [ED]). Linear regression: solid line=best fit line, shaded area=95% confidence limits, dashed line=95% prediction limits, P values computed via linear regression t test. Whisker plot: b=slope in $\hat{y}=a+bx$, bars=95% confidence limits of slope. 3D indicates 3-dimensional; APC, anterior posterior commissure; ASC, anterior septal commissure; BC, Box-Cox Transformation: $y_i=\left(y_i^{\lambda }-1\right)/\lambda$; and PSC, posterior septal commissure.