CARD32: Fontan Assist Device: Investigation of hemodynamic effects and wall shear stress using a cardiovascular simulator with computational fluid dynamic coupling

Abstract

Study: The Fontan Assist Device (FAD), comprising of two tiny axial pumps, has potential use for single-ventricle patients by providing support for pulmonary blood flow and mitigating chronic venous hypertension. This study examines the FAD’s effects on hemodynamics under various medications and provides a method to assess wall shear stress (WSS) on the Fontan structure throughout the cardiac cycle. Method: A 0D lumped parameter model of the Fontan circulation was created in Matlab Simulink and tuned from patient-specific clinical data. For FAD evaluation, two axial pumps were placed in the pulmonary arteries. Changes in hemodynamic conditions with FAD +/- medical therapy (vasodilator and/or diuretic) were modeled and compared to the baseline condition. For 3D analysis of the FAD in situ, the segmented Fontan anatomy was obtained for computational fluid dynamics (CFD) assessment in Ansys CFX. 0D and 3D models were coupled to account for physiological changes simulated in 0D on the 3D boundary conditions. The FAD was modelled as two cylindrical momentum sources. Result: In 0D: At baseline, cardiac output (CO) was 4.2 L/min, and Fontan pressure was 16 mmHg. With FAD, CO improved to 5.1 L/min and could reach higher with vasodilator. Venous pressure can be reduced to 8 mmHg when paring with diuretic treatment. FAD + vasodilator + diuretic achieved venous pressure of 12.4 mmHg, Fontan pressure of 12.1 mmHg and CO of 5.0 L/min. In 0D-3D: cardiac output increased to 5.2 L/min with FAD compared to 4.6 L/min without while WSS also increased from 2.33 Pa to 10.2 Pa in the right pulmonary arteries. Future work includes optimizing both the design and placement of the FAD.Figure 1. 0D model pressure waveform of baseline condition and with different medical treatmentsFigure 2. Shear stress of baseline conditionFigure 3. Shear stress with FAD treatment