Poster U1 - Virtual Surgery Treatment Planning in Hypoplastic Left Heart Syndromes with Interrupted Inferior Vena Cava

Introduction: Hypoplastic Left Heart Syndrome (HLHS) with interrupted inferior vena cava (IVC) poses significant surgical challenges, particularly to re-direct the hepatic vein flow through vena cava pathways. Interrupted IVC is a rare condition where the infrahepatic portion of the IVC is absent, a result of the failure of the vitelline and subcardinal veins to fuse during embryological development. Interrupted IVC is often characterized by the continuation of the hepatic venous return through an enlarged azygos or hemiazygos vein, which then drains into the superior vena cava or brachiocephalic veins. Current surgical approaches, such as the extracardiac conduit (ECC) and H-graft placement, can yield suboptimal outcomes. This study investigates the potential of virtual surgery in optimizing surgical plans, comparing H-graft configurations against ECC, to enhance hemodynamic outcomes and help mitigating pulmonary arterial hypertension (PAH) commonly seen post-intervention.

Materials and

Methods: This study utilized retrospective computational fluid dynamics (CFD) simulations using HARVEY, a massively paralleled CFD solver and based on 3D MRI scan of an HLHS patient with interrupted IVC. Patient-specific anatomy was reconstructed from 3D MRI scan with flow wave forms in major branches quantified from phase-contrast MRIs. Simulations of H-graft and ECC configurations were performed at 3 candidate graft diameters (Figure 1A), i.e., 10, 12, and 14 mm, to assess their effects on time-average wall shear stress (TAWSS; the friction of flowing blood on the artery wall) and blood flow distribution. Inlet boundary condition was updated at the hepatic ends to account for re-directed hepatic flow (right hepatic vein average flow = 2.89 mL/sec , left hepatic vein average flow = 2.54 mL/sec; total hepatic flow = 5.43 mL/sec) post-intervention (Figure 1A). Hemodynamic parameters were statistically analyzed using one-way ANOVA with Tukey’s post hoc test.

Results, Conclusions, and Discussions: CFD simulations revealed significant changes in TAWSS across various surgical configurations (Figure 1B), notably in the pulmonary arteries, the azygos vein, and the superior vena cava (SVC). In the pulmonary arteries, both ECC and H-graft surgeries improved TAWSS: ECC increased it by a mean difference of 0.184 (95% CI [0.1712, 0.1968], p < 0.001), and H-graft by 0.1783 (95% CI [0.1655, 0.1911], p < 0.001). The SVC also showed significant improvements as indicated in Figure 2A; ECC increased TAWSS by 0.0254 (95% CI [0.0122, 0.0386], p < 0.001) and H-graft by 0.0241 (95% CI [0.0109, 0.0373], p = 0.0001), with no significant difference between them (-0.0013, 95% CI [-0.0145, 0.0119], p = 0.9714). In the azygos vein, H-graft significantly increased TAWSS from the baseline (mean difference of 0.1165, p < 0.001) and relative to ECC (mean difference of 0.1109, p < 0.001), indicating a substantial enhancement in local hemodynamics specific to this surgical procedure (Figure 2B). Furthermore, pulmonary artery flow ratios demonstrated that ECC configurations provided a more balanced flow between the right and left pulmonary arteries, with ratios nearing 1:1 (ECC 10 mm: 1.11, ECC 12 mm: 1.13, ECC 14 mm: 1.15) compared to H-graft (H-graft 10 mm: 1.27, H-graft 12 mm: 1.31, H-graft 14 mm: 1.33), suggesting a more symmetrical hemodynamic distribution with ECC. A closer balance of flow maintained in ECC surgical configurations might be preferable for achieving optimal physiological outcomes and symmetry of flow distribution post-intervention. The H-graft, while causing some imbalance in flow ratios, proved particularly beneficial in improving critical hemodynamic parameters in regions susceptible to low shear stress. These findings underscore the utility of virtual surgery in pre-surgical planning for complex cardiovascular conditions like HLHS with interrupted IVC. By enabling precise modeling of surgical scenarios, clinicians can predict and optimize outcomes, customizing treatments to patient-specific anatomical and physiological needs. The comparative effectiveness of ECC and H-graft in improving TAWSS across different vascular regions provides critical insights into selecting surgical strategies. This research supports the broader adoption of computational techniques in pediatric cardiology, enhancing surgical precision and potentially leading to better patient outcomes.

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