Apical inflow is associated with increased energy loss during left ventricular diastole in patients with a repaired atrioventricular septal defect: a 4D flow MRI study
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KeywordsAtrioventricular Valve Apical Level Valve Morphology Atrioventricular Septal Defect Left Ventricular Diastole
Patients after atrioventricular septal defect (AVSD) repair have aberrant atrioventricular valve morphology resulting in a disorganized left ventricular (LV) inflow  with an increased amount of inflow reaching the apical level of the LV and retaining there during the subsequent systole .This may elevate energy loss in LV flow due to friction. We aimed to evaluate the association between the percentages (retained) apical inflow with viscous energy loss during diastole in AVSD-repaired patients compared to healthy controls using 4D flow MRI.
21 AVSD-repaired patients (age: 33 ± 9 years) and 16 healthy controls (age: 35 ± 11 years, p = 0.52) underwent free-breathing whole-heart 4D flow MRI at 3T(VENC =150 cm/s in all directions, spatial resolution 2.3 × 2.3 × 3.0-4.2 mm3, 30 retrospectively reconstructed phases over a cardiac cycle). The workflow in  was used to compute, relative to total inflow, percentages of apical inflow (AI%: inflow that reaches apical level during diastole), and retained apical inflow (RAI%: part of apical inflow that is not ejected during subsequent systole). The LV was segmented and the total non-turbulent viscous energy loss was computed over diastole (EL_diastole in Joule (J)) using the Navier-Stokes energy equations . The 95%CI (confidence interval) for AI% and RAI% was computed from healthy controls. Patients were then classified as: below or above upper limit of 95%CI of AI%, and below or above upperlimit of 95%CI of RAI%. Parameters were compared using Student's t-test. Association between EL_diastole with AI% and RAI% was evaluated using Pearson's correlation.
This is the first study to reveal the adverse impact of increased (retained) apical inflow on LV energy loss. Elevated viscous energy loss in patients reflects increased blood flow friction. This could potentially result in apical blood stagnation. Future-studies are needed to assess the impact of the reported association on LV function. The provided 4D flow workflow may permit a non-invasive tool to assess blood inflow efficiency in different patient groups.
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