Patient-specific CFD models for intraventricular flow analysis from 3D ultrasound imaging: Comparison of three clinical cases

Abstract

Background: As the intracardiac flow field is affected by changes in shape and motility of the heart, intraventricular flow features can provide diagnostic indications. Ventricular flow patterns differ depending on the cardiac condition and the exploration of different clinical cases can provide insights into how flow fields alter in different pathologies.

Methods: In this study, we applied a patient-specific computational fluid dynamics model of the left ventricle and mitral valve, with prescribed moving boundaries based on transesophageal ultrasound images for three cardiac pathologies, to verify the abnormal flow patterns in impaired hearts. One case (P1) had normal ejection fraction but low stroke volume and cardiac output, P2 showed low stroke volume and reduced ejection fraction, P3 had a dilated ventricle and reduced ejection fraction.

Results: The shape of the ventricle and mitral valve, together with the pathology influence the flow field in the left ventricle, leading to distinct flow features. Of particular interest is the pattern of the vortex formation and evolution, influenced by the valvular orifice and the ventricular shape. The base-to-apex pressure difference of maximum 2mmHg is consistent with reported data.

Conclusion: We used a CFD model with prescribed boundary motion to describe the intraventricular flow field in three patients with impaired diastolic function. The calculated intraventricular flow dynamics are consistent with the diagnostic patient records and highlight the differences between the different cases. The integration of clinical images and computational techniques, therefore, allows for a deeper investigation intraventricular hemodynamics in patho-physiology.

Keywords: CFD with prescribed moving boundaries; Intraventricular flow; Patient-specific models; Ventricular vortex analysis.

Figure 1

upper panel: patient geometries, showing the anterolateral and posterior walls of the LV. The dimensions of the major (Ax₁) and minor (Ax₂) axes are reported in table 1. Lower panel: LV volume curves calculated from the segmented ventricles. Sections S₁, CS₁ and CS₂ used to report relevant results in figure 2 and 3.

Figure 2

moving walls and valvular leaflets in the three patients at late systole, E-peak and late diastole.

Figure 3

Intraventricular flow on a 2D slice and pressure variations (section S₁ indicated in fig.1) at four relevant time-points. Right panels: volume flow rate curve (solid line), calculated at the atrial inlet, intraventricular pressure gradient, calculated as the difference of the average pressure between the cross section 1 and 2 (CS₁ and CS₂) of figure 1. Note that the scale of the pressure changes in each panel.

Figure 4

Intraventricular vortex visualization (λ₂) and velocity streamlines at four relevant time-points. Right panels: flow curve and viscous energy dissipation curve.