Abstract
The aim of the current study was to assess the scan–rescan reproducibility of left ventricular (LV) kinetic energy (KE), viscous energy loss (EL) and vorticity during diastole from four-dimensional flow magnetic resonance imaging (4D flow MRI) in healthy subjects. Twelve volunteers (age 27 ± 3 years) underwent whole-heart 4D flow MRI twice in one session. In-scan consistency was evaluated by correlation between KE and EL. ELindex was computed to measure the amount of EL relative to KE over diastole. Scan–rescan analysis was performed to test reproducibility of volumetric measurements of KE, EL, ELindex and vorticity in the LV over early (E) and late (A) diastolic filling. In-scan consistency between KE and EL was strong-excellent (E-filling scan1: r = 0.92, P < 0.001; scan2: ρ = 0.96, P < 0.001 and A-filling scan1: ρ = 0.87, P < 0.001; scan2: r = 0.99, P < 0.001). For the majority of subjects (10 out of 12), KE and EL measures showed good to strong reproducibility. However, with a wide range of agreement [intraclass correlation (ICC): 0.64–0.95] and coefficients of variation (CV) ≤ 25%. ELindex showed strong reproducibility for all 12 subjects with a strong ICC (0.94, P < 0.001) and a CV of 9%. Scan–rescan reproducibility of volumetric vorticity showed good–excellent ICCs (0.83–0.95) with CVs ≤ 11%. In conclusion, the current study shows strong–excellent in-scan consistency and overall good agreement between scans for 4D flow MRI assessment of left ventricular kinetic energy, energy loss and vorticity over diastole. However, substantial differences between the scans were also found in some parameters in two out of twelve subjects. Strong reproducibility was found in the dimensionless ELindex, which measures the amount of viscous energy loss relative to the average kinetic energy over diastole.
Highlights
Congenital and acquired heart diseases affect the efficacy of intracardiac flow patterns and energy distribution [1, 2]
Kinetic energy, viscous energy loss and vorticity inside the left ventricle during diastole are derived from 4D flow MRI and scan–rescan reproducibility of these parameters is tested
Scan–rescan reproducibility is essential for the clinical application of a parameter since it reflects the reliability of a measurement and feasibility of repeated measurement evaluations
Summary
Congenital and acquired heart diseases affect the efficacy of intracardiac flow patterns and energy distribution [1, 2]. The International Journal of Cardiovascular Imaging (2018) 34:905–920 intraventricular KE derived from 4D flow MRI has been used to assess left ventricular (LV) and right ventricular (RV) (dys)function in patients with different stages of heart failure (HF) [4,5,6,7] This is the case in various congenital heart diseases. The curl of velocity, is a fundamental quantity in fluid mechanics that describes the local spinning rate of fluid particles and can characterize vortex flow [10] Quantitative vortex parameters, such as vorticity, have been used to assess diastolic (dys) function in several patient groups [8, 9, 11, 12]. In patients with complex congenital intracardiac deformations such as after the Fontan operation, flow collision with remaining septal structures and stagnation of flow through a ventricular septal defect may result in altered EL and vortex formation [13]
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