WTSA - Fontan Surgery in Patients with an Interrupted IVC: Guidelines for Optimizing the Hepatic Baffle Design


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Fontan Surgery in Patients with an Interrupted IVC: Guidelines for Optimizing the Hepatic Baffle Design

Diane A de Zelicourt¹, Christopher M Haggerty¹, Kartik S Sundareswaran¹, Brian S Whited¹, Jarek R Rossignac¹, Mark A Fogel², *Kirk R Kanter³, *William J Gaynor², *Thomas L Spray², Ajit P Yoganathan¹
¹Georgia Institute of Technology, Atlanta, GA;²Children's Hospital of Philadelphia, Philadelphia, PA;³Emory University School of Medicine, Atlanta, GA

BACKGROUND: Single-ventricle patients with interrupted inferior vena cava (IVC) and azygos continuation commonly require a Fontan connection after the Kawashima procedure to reverse the development of pulmonary arteriovenous malformations (PAVMs). However, in a few cases, the design of the hepatic baffle (HB), relative to the existing anatomy, results in an unbalanced hepatic flow distribution (HFD) to the lungs and subsequent recurrence of PAVMs. In this study, we combine virtual surgery and numerical simulations to identify the optimal HB designs for patients with interrupted IVC.
METHODS: Six patients with interrupted IVC and severe PAVMs were separated into two groups. Group 1 (G1: n=3) patients had a single superior vena cava (SVC), while Group 2 (G2: n=3) patients had a persistent left SVC (LSVC). In vivo anatomies were reconstructed from MRI (n=4) and CT (n=2). Using a virtual-surgery interface, nine possible HB designs, on average, were generated for each patient. The options considered included various HB-to-SVC offsets, intra and extra-cardiac baffles, and HB-to-azygos and azygos-to-HB connections. HFD was assessed for all options using a fully validated computational flow solver.
RESULTS: For all cases, HFD was very sensitive to the HB-to-SVC offset. For G1 (Figure 1), simply connecting the HB to the Kawashima connection proved dangerous, as even a small left or right offset led to a highly preferential HFD to the associated lung because of the greater momentum carried by the superior return. Best results were obtained with either a Y-shaped HB to evenly split the flow (1 pt), or an HB-to-azygos connection to promote mixing in the Kawashima (2 pts). In G2 (Figure 2), optimal results were obtained by centrally connecting the HB between the SVCs. Options with a biased HB orientation (left or right) led to highly preferential HFD to the associated lung. One major exception was found for one patient who had a significant imbalance in the distribution of the superior return. Specifically, the SVC and right-sided azygos carried 70% of the cardiac output, forcing the hepatic flow (only 10% CO) to the left. This configuration was found to be more like G1 cases, and the optimal solution was a combination azygos-to-HB and Y-graft. This case underscores the importance of pre-operative flow assessment with MRI for characterizing the existing hemodynamics of the connection. Although post-operative MRI data are lacking, the use of these approaches has generally led to increased oxygen saturations testifying for improved HFD.
CONCLUSION: Our experience of surgical planning for six Fontan patients with an interrupted IVC has demonstrated that, by properly characterizing pre-operative anatomy and hemodynamics in these complex patients, a set of simple yet efficient guidelines can be defined to optimize HFD and ultimately minimize the chances of PAVMs.

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