4D Flow MRI Velocity and Turbulence Mapping in Mild Valvular Heart Disease.

Background: Valvular heart disease (VHD) commonly leads to the development of turbulent blood flow. Turbulent kinetic energy (TKE), measured with 4D flow MRI, may be a complement to current metrics for early identification of VHD.

Purpose: To investigate TKE as a marker of VHD in relation to flow velocity and cardiovascular geometry.

Study Type: Retrospective observational cross-sectional.

Population: Twenty controls and 106 subjects with VHDs, including mitral regurgitation, aortic regurgitation, pulmonary regurgitation, tricuspid regurgitation, and aortic stenosis.

Field Strength/sequences: Four-dimensional flow MRI using a spoiled gradient-echo phase-contrast sequence with asymmetric 4-point motion encoding at 1.5 or 3 T.

Assessment: Time-resolved segmentations of the left and right ventricles (LV, RV), atria (LA, RA), and aorta were performed. Total and maximum TKE, maximum and average velocity, and diameters were evaluated in each. Correlations between TKE, velocity, and diameter were assessed, along with group differences between VHD subjects and controls.

Statistical Tests: Student's t-test, Wilcoxon rank-sum test, chi-squared test, Pearson's correlation, two-way analysis of covariance. A p value < 0.05 was considered significant.

Results: Total and maximum TKE correlated significantly with maximum velocity (r = 0.45-0.76) and averaged velocity (r = 0.22-0.44) and less strongly with diameters for aorta, LV, LA, and RV (r = 0.18-0.37). Compared to controls, total and maximum aortic TKE were significantly higher in aortic stenosis (3.8 vs. 1.6 mJ; 291.7 vs. 133.7 J/m). Maximum LV TKE was significantly elevated in aortic regurgitation (106.6 vs. 91.8 J/m). Total TKE was significantly elevated in LA for mitral regurgitation (1.1 vs. 0.6 mJ), in RA for tricuspid regurgitation (1.6 vs. 0.7 mJ), and in RV for pulmonary regurgitation (1.7 vs. 1.0 mJ).

Data Conclusion: TKE is elevated in mild VHD. When evaluated alongside velocity as a marker for VHD, TKE may be more discriminative. Consequently, it has potential to be a hemodynamic marker of early VHD conveying complementary information to velocity.

Evidence Level: 4.

Technical Efficacy: Stage 1.