A Novel In Vitro Fontan Circulation Mock Loop for Testing Flow Dynamics and Mechanical Assist Devices

The Thoracic and Cardiovascular Surgeon, vol. 74, pp. S1–S70

Abstract

All articles of this category (opens in new window) Background: As a basis for comprehensive research in the field of the Failing Fontan, an in vitro Fontan Circulation mock loop would be desirable. We sought to develop such a model. Methods: The model was constructed using clinical-grade cardiopulmonary bypass components, including 3/8 inch tubing and peristaltic pumps. A custom-made compliance chamber was used in the “systemic” circulation. The two lungs were represented by air-tight cardiotomy reservoirs with a pneumatically adjustable air access, allowing modulation of resistance. The working fluid consisted of glycerin and distilled water, mimicking a physiologic blood density. Different anatomic and functional types of total cavo-pulmonary connections were analyzed, like caval offset, flaring of the anastomosis, bilateral superior caval veins, and azygos continuity. Ports for insertion of “subpulmonary” and “systemic” assist devices were integrated. Visual flow analysis was achieved using food coloring. Flow behavior was recorded with a camera and analyzed using RGB color analysis, which quantifies the red, green, and blue color intensities (0–255) from digital images. Measurements were performed in the inflow regions (superior vena cava (SVC), inferior vena cava (IVC)) and outflow regions (left and right pulmonary arteries (PAs)), and results were compared with real-time flow velocity data (transonic, ELSA H9FX flow sensors), and pressure data were recorded, respectively. Results: Different anatomic and functional variations were successfully established and analyzed by pressure, flow, and color studies. The RGB values in the PAs correlated with the flow rates, and visual RGB analysis clearly showed the volume fraction from each caval vein and its distribution to the PAs. For example, in the bilateral SVC model (Blue: IVC, Yellow: right SVC, Red: left SVC), LPA was perfused almost entirely by LSVC and IVC (RGB: 28;4;28), RPA mainly by RSVC (RGB: 9;77;15). A total of 12 axial flow pump insertion processes were uncomplicated (subpulmonary 65 ± 14 seconds, systemic 45 ± 12 seconds). Conclusion: This mock loop represents a functional model of the Fontan circulation mimicking selected patients’ situations. Its modular and accessible design allows for rapid modeling of patient-specific anatomy and hemodynamics, supporting individualized surgical planning. The in vitro model will serve as a preliminary testing platform for novel assist devices in the treatment of failing Fontan circulation. Publication History Article published online: 17 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

Authors 12

1. C. Ciobotaru

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

2. Martin Eide

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

3. G Lutter

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

4. Hanna Gravert

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

5. B. Panholzer

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

6. Jens Scheewe

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

7. JH. Hansen

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

8. Jill Jussli-Melchers

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

9. Anselm Sebastian Uebing

   University Hospital Schleswig-Holstein

   Affiliation as printed

   Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

10. G. Warnecke

    University Hospital Schleswig-Holstein

    Affiliation as printed

    Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland

11. C. Feldmann Aachen Fachhochschule Aachen

    FH Aachen

    Affiliation as printed

    Fachhochschule Aachen, Campus Jülich, Heinrich-Mußmann-Straße, Jülich, Germany, Jülich, Deutschland

12. Tim Attmann

    University Hospital Schleswig-Holstein

    Affiliation as printed

    Universitätsklinikum Schleswig-Holstein, Campus Kiel, Arnold-Heller-Straße, Kiel, Deutschland, Kiel, Deutschland