Factors influencing the end‐diastolic vortex assessed by using vector flow mapping

Age-Related Changes in Left Ventricular Vortex Formation and Flow Energetics

Analysis of the cardiac vortex has been used for a deeper understanding of the pathophysiology in heart diseases. However, physiological changes of the cardiac vortex with normal aging are incompletely defined. Vector flow mapping (VFM) is a novel echocardiographic technique based on Doppler and speckle tracking for analysis of the cardiac vortex. Transthoracic echocardiography and VFM analysis were performed in 100 healthy adults (33 men; age = 18–67 years). The intracardiac flow was assessed throughout the cardiac cycle. The size (cross-sectional area) and circulation (equivalent to the integral of normal component of vorticity) of the largest vortices in systole (S-vortex), early diastole (E-vortex), and late diastole (A-vortex) were measured. Peak energy loss (EL) was calculated from information of the velocity vector of intracardiac flow in systole and diastole. With normal aging, the circulation (p = 0.049) of the E-vortex decreased, while that of the A-vortex increased (both p < 0.001). E-vortex circulation correlated directly to e’ (p = 0.003), A-vortex circulation correlated directly to A and a’ (both p < 0.001), and S-vortex circulation correlated directly to s’ (p = 0.032). Despite changes in vortex patterns, energy loss was not significantly different in older individuals. Normal aging is associated with altered intracardiac vortex patterns throughout the cardiac cycle, with the late-diastolic A-vortex becoming physiologically more dominant. Maintained energy efficiency accompanies changes in vortex patterns in aging hearts.

Functional significance of intra-left ventricular vortices on energy efficiency in normal, dilated, and hypertrophied hearts

PURPOSE

To investigate the influence of changes in vortices within the left ventricle (LV) on energy efficiency (EE) in normal and diseased hearts.

METHODS

We performed vector flow mapping echocardiography in 36 normal participants (N), 36 patients with dilated cardiomyopathy (D), and 36 patients with LV hypertrophy (H). The circulation of the main anterior vortex was measured as a parameter of vortex strength. Energy loss (EL) was measured for one cardiac cycle, and EE was calculated as EL divided by stroke work (SW), which represents the loss of kinetic energy per unit of LV external work.

RESULTS

Circulation increased in the order of N, H, and D (N: 15 ± 4, D: 19 ± 8, H: 17 ± 6 × 10^-3 m² /s; analysis of variance [ANOVA] P < .01). Conversely, EE increased in the order of N, D, and H (N: 0.22 ± 0.07, D: 0.26 ± 0.16, H: 0.30 ± 0.16 10^-5 J/mm Hg mL m s; ANOVA P = .04), suggesting worst EE in group H. We found a positive correlation between circulation and SW only in group N, and positive correlation between circulation and EE only in diseased groups (D: R = 0.55, P < .01; H: R = 0.44, P < .01). Multivariable analyses revealed that circulation was the independent determinant of EE in groups D and H.

CONCLUSIONS

Enhanced vortices could be associated with effective increase in LV external work in normal hearts. Conversely, they were associated with loss of EE without an optimal increase in external work in failing hearts, regardless of the LV morphology.

Numerical simulations of flow patterns in the human left ventricle model with a novel dynamic mesh morphing approach based on radial basis function

We present a new numerical simulation framework for prediction of flow patterns in the human left ventricle model. In this study, a radial basis function (RBF) mesh morphing method is developed and applied within the finite-volume computational fluid dynamics (CFD) approach. The numerical simulations are designed to closely mimic details of recent tomographic particle image velocimetry (TomoPIV) experiments. The numerically simulated dynamic motions of the left ventricle and tri-leaflet biological mitral valve are emulated through the RBF morphing method. The arbitrary Lagrangian-Eulerian (ALE) based CFD is performed with the RBF-defined deforming wall boundaries. The results obtained show a good agreement with experiments, confirming the reliability and accuracy of the developed simulation framework.