Vortex formation time as an index of left ventricular filling efficiency: comparison between children volunteers and patients with tetralogy of Fallot

BACKGROUND: Vortex formation time (VFT) had been considered a useful marker for assessing diastolic performance. the VFT assessment of diastolic function using four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has not been used in repair of tetralogy of Fallot (rTOF) patient. The aims of this study were as follows: (I) establish reference ranges for VFT measurements in healthy children and adolescents using 4D flow CMR imaging; and (II) analyze VFT parameters to assess diastole dysfunction in rTOF patients group. METHODS: We acquired the CMR data was of 62 healthy participants (aged 6–18 years; male: 40, female: 22) and 20 patients with rTOF (aged 10–13 years; male: 15, female: 5) using 4D flow and cine sequence in routine chamber view. The VFT was calculated based on comparison of different algorithms from cine measurements (VFT(volume)) and 4D flow measurements (VFT(blood)). Then, VFT measurements were compared to subject peak filling rate (PFR), age, and cardiac mass using simple linear regression and multiple regression analyses. Data were also categorized according to age for VFT and cardiac functional assessment comparisons between 3 age groups (Group 1: 6–9 years; Group 2: 10–13 years; Group 3: 14–18 years). The correlation of VFT and cardiac function parameters were analyzed in the rTOF group. RESULTS: Normal mean value of VFT(volume) and VFT(blood) were 4.25±0.92 and 3.77±1.11 in healthy children participants. The VFT(volume) was correlated with VFT(blood) (r=0.61, P<0.001). There was a moderately significant correlation between VFT(volume) and PFR (r=0.46, P<0.001) and between VFT(blood) and PFR (r=0.47, P<0.001), age (r=0.41, P=0.002) and left ventricular (LV) mass (r=0.48, P<0.001). Multiple regression analyses demonstrated that VFT(volume) was independently associated with PFR (T=2.239; P<0.05) and VFT(blood) (T=4.361; P<0.001). There was a significant difference in VFT(volume) between healthy controls and rTOF patients (5.44±1.93 vs. 4.27±0.88, P=0.018). CONCLUSIONS: The VFT measurements showed that the LV that had appropriate space to form the optimal vortex ring in normal children and adolescents aged 6–18 years old. The VFT(volume) could potentially be helpful in improving our understanding of LV diastolic dysfunction in rTOF patients.