Vortex-ring mixing as a measure of diastolic function of the human heart: Phantom validation and initial observations in healthy volunteers and patients with heart failure

Purpose To present and validate a new method for 4D flow quantification of vortex-ring mixing during early, rapid filling of the left ventricle (LV) as a potential index of diastolic dysfunction and heart failure. Materials and Methods 4D flow mixing measurements were validated using planar laser-induced fluorescence (PLIF) in a phantom setup. Controls (n = 23) and heart failure patients (n = 23) were studied using 4D flow at 1.5T (26 subjects) or 3T (20 subjects) to determine vortex volume (VV) and inflowing volume (VV_inflow). The volume mixed into the vortex-ring was quantified as VV_mix-in = VV-VV_inflow. The mixing ratio was defined as MXR = VV_mix-in/VV. Furthermore, we quantified the fraction of the end-systolic volume (ESV) mixed into the vortex-ring (VV_mix-in/ESV) and the fraction of the LV volume at diastasis (DV) occupied by the vortex-ring (VV/DV). Results PLIF validation of MXR showed fair agreement (R² = 0.45, mean ± SD 1 ± 6%). MXR was higher in patients compared to controls (28 ± 11% vs. 16 ± 10%, P < 0.001), while VV_mix-in/ESV and VV/DV were lower in patients (10 ± 6% vs. 18 ± 12%, P < 0.01 and 25 ± 8% vs. 50 ± 6%, P < 0.0001). Conclusion Vortex-ring mixing can be quantified using 4D flow. The differences in mixing parameters observed between controls and patients motivate further investigation as indices of diastolic dysfunction.