Systolic reverse flow derived from 4D flow cardiovascular magnetic resonance in bicuspid aortic valve is associated with aortic dilation and aortic valve stenosis: a cross sectional study in 655 subjects

Abstract

Background Bicuspid aortic valve (BAV) disease is associated with increased risk of aortopathy. In addition to current intervention guidelines, BAV mediated changes in aortic 3D hemodynamics have been considered as risk stratification measures. We aimed to evaluate the association of 4D flow cardiovascular magnetic resonance (CMR) derived voxel-wise aortic reverse flow with aortic dilation and to investigate the role of aortic valve regurgitation (AR) and stenosis (AS) on reverse flow in systole and diastole. Methods 510 patients with BAV (52 ± 14 years) and 120 patients with trileaflet aortic valve (TAV) (61 ± 11 years) and mid-ascending aorta diameter (MAAD) > 35 mm who underwent CMR including 4D flow CMR were retrospectively included. An age and sex-matched healthy control cohort (n = 25, 49 ± 12 years) was selected. Voxel-wise reverse flow was calculated in the aorta and quantified by the mean reverse flow in the ascending aorta (AAo) during systole and diastole. Results BAV patients without AS and AR demonstrated significantly increased systolic and diastolic reverse flow (222% and 13% increases respectively, p < 0.01) compared to healthy controls and also had significantly increased systolic reverse flow compared to TAV patients with aortic dilation (79% increase, p < 0.01). In patients with isolated AR, systolic and diastolic AAo reverse flow increased significantly with AR severity (c = − 83.2 and c = − 205.6, p < 0.001). In patients with isolated AS, AS severity was associated with an increase in both systolic (c = − 253.1, p < 0.001) and diastolic (c = − 87.0, p = 0.02) AAo reverse flow. Right and left/right and non-coronary fusion phenotype showed elevated systolic reverse flow (> 17% increase, p < 0.01). Right and non-coronary fusion phenotype showed decreased diastolic reverse flow (> 27% decrease, p < 0.01). MAAD was an independent predictor of systolic (p < 0.001), but not diastolic, reverse flow (p > 0.1). Conclusion 4D flow CMR derived reverse flow associated with BAV was successfully captured even in the absence of AR or AS and in comparison to TAV patients with aortic dilation. Diastolic AAo reverse flow increased with AR severity while AS severity strongly correlated with increased systolic reverse flow in the AAo. Additionally, increasing MAAD was independently associated with increasing systolic AAo reverse flow. Thus, systolic AAo reverse flow may be a valuable metric for evaluating disease severity in future longitudinal outcome studies.

Four-dimensional flow cardiovascular magnetic resonance aortic cross-sectional pressure changes and their associations with flow patterns in health and ascending thoracic aortic aneurysm

“…Such backward flow, which starts during late systole and persists until late diastole, has been attributed to the local reversal of pressure gradients [41] , [42] , inducing a local reversal in blood flow, captured by the velocity sign on either 2D or 4D phase contrast CMR images. Flow reversal patterns are mostly located in the curved segments of the aorta [40] , which is in line with the higher convective relative pressures observed in the external part of such segments [18] and with cross-sectional changes in aortic pressure gradients found in our study.…”

“…Of note, WSS and vorticity values obtained in our population are in the same range as values provided in the above-mentioned WSS [32] , [37] , [38] and vorticity [12] studies. One might highlight however that changes in flow patterns in the thoracic aorta have been widely described through the quantitative evaluation of backward flow from 2D phase-contrast MRI [39] and more recently from 4D flow CMR [40] . Such backward flow, which starts during late systole and persists until late diastole, has been attributed to the local reversal of pressure gradients [41] , [42] , inducing a local reversal in blood flow, captured by the velocity sign on either 2D or 4D phase contrast CMR images.…”

Aortic flow is associated with aging and exercise capacity

“…Several studies investigating AO root dilatation have already studied systolic FD. 17 , 29 , 30 Not only is FD associated with AO dilatation, but it can also predict further dilatation at 1-year follow-up, 18 and is significantly linked to LV remodelling in patients with AO stenosis. 31 Similar observations were made by Albarran et al in pre-clinical pig models.…”