Non-uniform mixing of hepatic venous flow and inferior vena cava flow in the Fontan conduit.

Friso M Rijnberg,Arno A W Roest,Sasa Kenjeres,Monique R M Jongbloed,Hans C Van Assen,Hildo J Lamb,Jolanda J Wentzel,Joe F Juffermans,Mark G Hazekamp,Jos J M Westenberg,Séline F S Van Der Woude

doi:10.1098/rsif.2020.1027

Abstract

Fontan patients require a balanced hepatic blood flow distribution (HFD) to prevent pulmonary arteriovenous malformations. Currently, HFD is quantified by tracking Fontan conduit flow, assuming hepatic venous (HV) flow to be uniformly distributed within the Fontan conduit. However, this assumption may be unvalid leading to inaccuracies in HFD quantification with potential clinical impact. The aim of this study was to (i) assess the mixing of HV flow and inferior vena caval (IVC) flow within the Fontan conduit and (ii) quantify HFD by directly tracking HV flow and quantitatively comparing results with the conventional approach. Patient-specific, time-resolved computational fluid dynamic models of 15 total cavopulmonary connections were generated, including the HV and subhepatic IVC. Mixing of HV and IVC flow, on a scale between 0 (no mixing) and 1 (perfect mixing), was assessed at the caudal and cranial Fontan conduit. HFD was quantified by tracking particles from the caudal (HFDcaudal conduit) and cranial (HFDcranial conduit) conduit and from the hepatic veins (HFDHV). HV flow was non-uniformly distributed at both the caudal (mean mixing 0.66 ± 0.13) and cranial (mean 0.79 ± 0.11) level within the Fontan conduit. On a cohort level, differences in HFD between methods were significant but small; HFDHV (51.0 ± 20.6%) versus HFDcaudal conduit (48.2 ± 21.9%, p = 0.033) or HFDcranial conduit (48.0 ± 21.9%, p = 0.044). However, individual absolute differences of 8.2–14.9% in HFD were observed in 4/15 patients. HV flow is non-uniformly distributed within the Fontan conduit. Substantial individual inaccuracies in HFD quantification were observed in a subset of patients with potential clinical impact.

Highlights

The Fontan operation is the palliative procedure for single-ventricle patients, in which both venae cavae are connected with the pulmonary arteries (PAs), called the total cavopulmonary connection (TCPC)
Patient characteristics and magnetic resonance imaging (MRI) flow measurements are presented in table 1
An evident streaming pattern of hepatic venous (HV) flow within the Fontan conduit was present resulting in non-uniform distribution of HV flow within the Fontan conduit, most shown in the caudal part of the Fontan conduit

Summary

Introduction

The Fontan operation is the palliative procedure for single-ventricle patients, in which both venae cavae are connected with the pulmonary arteries (PAs), called the total cavopulmonary connection (TCPC). BSA, body surface area (Haycock); MRI, magnetic resonance imaging; ECC, extracardiac conduit; LT, lateral tunnel; Q, flowrate; IVC, inferior vena cava; HV, hepatic veins. Patient-specific platforms using a combination of computational fluid dynamics (CFD) and magnetic resonance imaging (MRI) are emerging as a valuable tool for clinicians for evaluating HFD and power loss [3,4]. These platforms allow for performing ‘virtual surgery’, by which multiple different TCPC geometries can be virtually created and associated blood flow can be predicted. The optimal TCPC geometry with minimal power loss and a balanced HFD can be determined thereby guiding surgical and catheter-based interventions [5,6]

Objectives

Results

Conclusion