Vortices and Hemodynamic Forces in the Left Ventricle: Comparison between High Frame Rate Echo-Particle Image Velocimetry and 4D Flow MRI

Objective
Assessing advanced blood flow parameters, such as hemodynamic forces (HDF) and vortex circulation (VC), may offer insights into cardiac function and remodeling. Vortices conserve energy and balance myocardial workload, with VC reflecting vortex intensity and size. HDF quantifies the intraventricular pressure gradients driving blood flow. This study compares HDF and VC between echoPIV and 4D flow MRI, as well as between patient groups.
Methods
We acquired high-frame-rate contrast-enhanced ultrasound (three apical views) and 4D flow MRI from 26 patients referred for cardiac MRI. Echo image planes with insufficient quality or poor alignment with MRI were excluded from the comparison. Time-trace correlation coefficients (of the time traces) and linear regressions of the temporal root mean square (RMS) values were used to compare HDF and VC between modalities.
Results
Echo and MRI measurements of longitudinal HDF (HDFlong) and principal VC showed strong correspondence. Correlation coefficients were 0.70 (HDFlong) and 0.66 (VC), with linear regression yielding r = 0.80 and r = 0.76 for HDF and VC RMS. Patients with impaired left ventricle systolic function showed significantly lower HDFlong and lower volume-normalized VC RMS.
Conclusion
EchoPIV accurately quantified HDFlong and VC across heart conditions, aligning closely with 4D flow MRI. Differences between echoPIV and MRI were smaller than those observed across pathology spectrum. Within this study cohort, HDFlong and VC magnitudes could be correlated to underlying heart conditions.