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Bicuspid aortic valve (BAV) is the most commonly diagnosed congenital heart defect with a prevalence ranging from 0.5 to 2% of the population1 and is often coincident with other congenital cardiovascular diseases, particularly left-sided obstructive lesions such as coarctation of the aorta.2 Pediatric BAV patients are known to have larger aortic dimensions than children with trileaflet valves, and are prone to progressive ascending aorta (AAo) dilatation.3 As these patients progress into adulthood, they are at increased risk for aortic dissection as a result of the disease4; however, the risk of primary cardiac events in childhood is minimal.5 Nonetheless, when diagnosed at an early age, BAV patients may require surgical intervention to normalize valve function and alter thoracic aorta anatomy in hopes of reducing long term risk.6 Time-resolved, three dimensional (3D) phase contrast (4D flow) MRI is increasingly used to study the role of cardiovascular hemodynamics in BAV.7 Recent studies in adult patients have shown that congenitally abnormal valves are associated with altered ascending aortic blood flow including high velocity outflow jet patterns and deranged helix and vortex type flow.8-12 Moreover, coarctation of the aorta can also result in varied hemodynamics in both the ascending and descending aorta in BAV patients.13 These hemodynamic alterations can result in changes in aortic wall shear stress (WSS) which have been shown to promote endothelial cell dysfunction and may ultimately lead to vascular remodeling.14 Elevated AAo WSS resulting from high velocity, asymmetric outflow jets in BAV patients has been hypothesized to play a role in progressive aortic dilatation in this cohort. Recent studies have demonstrated that adults with BAV have systematically higher and more asymmetric WSS relative to age and aortic size matched controls,9-11,15,16 and recent work by van Ooij et al using 4D flow MRI demonstrated increased volumetric WSS in the ascending aorta of adult BAV patients with aortic valve stenosis.17 Other hemodynamic parameters such as peak velocity, flow jet angle,18 and outflow eccentricity (flow displacement)19 have also been used in an attempt to quantify the impact of valvular heart disease on aortic hemodynamics. In the pediatric population, 4D flow MRI assessment has generally been described in small studies or case reports that have focused on patients with complex congenital heart or vascular defects or on postsurgical hemodynamics such as Fontan circulation.20-23 Truong et al recently used 2D phase contrast of the right pulmonary artery to measure WSS in children with pulmonary artery hypertension.24 However, the impact of BAV on changes in blood flow and the association with age and aortic size is poorly understood. In this pilot study, our aim was to describe the influence of BAV on thoracic aorta hemodynamic parameters in a group of pediatric and young adult patients using 4D flow MRI.

Doppler echocardiography (echo) is the reference standard for blood flow velocity analysis, and two-dimensional (2-D) phase-contrast magnetic resonance imaging (MRI) is considered the reference standard for quantitative blood flow assessment. However, both clinical standard-of-care techniques are limited by 2-D acquisitions and single-direction velocity encoding and may make them inadequate to assess the complex three-dimensional hemodynamics seen in congenital heart disease. Four-dimensional flow MRI (4-D flow) enables qualitative and quantitative analysis of complex blood flow in the heart and great arteries.The objectives of this study are to compare 4-D flow with 2-D phase-contrast MRI for quantification of aortic and pulmonary flow and to evaluate the advantage of 4-D flow-based volumetric flow analysis compared to 2-D phase-contrast MRI and echo for peak velocity assessment in children and young adults.Two-dimensional phase-contrast MRI of the aortic root, main pulmonary artery (MPA), and right and left pulmonary arteries (RPA, LPA) and 4-D flow with volumetric coverage of the aorta and pulmonary arteries were performed in 50 patients (mean age: 13.1 ± 6.4 years). Four-dimensional flow analyses included calculation of net flow and regurgitant fraction with 4-D flow analysis planes similarly positioned to 2-D planes. In addition, 4-D flow volumetric assessment of aortic root/ascending aorta and MPA peak velocities was performed and compared to 2-D phase-contrast MRI and echo.Excellent correlation and agreement were found between 2-D phase-contrast MRI and 4-D flow for net flow (r = 0.97, P 0.001) and excellent correlation with good agreement was found for regurgitant fraction (r = 0.88, P 0.001) in all vessels. Two-dimensional phase-contrast MRI significantly underestimated aortic (P = 0.032) and MPA (P 0.001) peak velocities compared to echo, while volumetric 4-D flow analysis resulted in higher (aortic: P = 0.001) or similar (MPA: P = 0.98) peak velocities relative to echo.Excellent flow parameter agreement between 2-D phase-contrast MRI and 4-D flow and the improved volumetric 4-D flow velocity analysis relative to echo suggests that 4-D flow has the potential to become a clinical alternative to 2-D phase-contrast MRI.

Background Echocardiography (echo) is the primary imaging modality for assessment of aortic and pulmonary blood flow velocities. 2D phase contrast (PC) MRI provides better access to all segments of the aortic and pulmonary system and is considered the standard for evaluating blood flow. Both techniques are limited by velocity analysis in 2D planes and by single-direction velocity measurement which may be inadequate to characterize the complex 3D hemodynamics in congenital heart disease (CHD). 4D flow MRI provides simultaneous assessment of 3D blood flow characteristics of all vessels within a 3D volume and offers the ability to retrospectively quantify blood flow parameters at selectable regions of interest. The aim of this study is to test the potential of 4D flow for accuracy of quantification of aortic and pulmonary flow parameters compared to the reference standards echo and 2D PC MRI in children and young adults with CHD. Methods 32 patients with CHD who underwent simultaneous 4D flow and 2D PC MRI and echo within 9 months of MRI were retrospectively included. 2D PC MRI flow quantification in the aortic root (Ao), pulmonary trunk (PT), and right and left pulmonary arteries (RPA, LPA) was analyzed using Medis (Medis, Leiden, The Netherlands). 4D flow data analysis included calculation of a 3D-PC-angiogram which was used to position analysis planes in the Ao, PT, LPA and RPA (EnSight, CEI, Apex, NC) for quantification of net flow, regurgitant fraction, Qp:Qs, and peak velocities. Ao peak velocities were assessed by echo. Linear regression analysis was performed. Pearson’ sc orrelation coefficient (r) was calculated. A correlation with p

Background Bicuspid aortic valve (BAV) is a congenital abnormality that is often associated with aortic coarctation. Evidence suggests this combination may increase the risk of secondary aortic complications compared to patients with BAV alone.[1] Altered aortic hemodynamics likely induce vascular remodeling[2] and may contribute to these complications. No study has investigated the impact of aortic coarctation on aortic hemodynamics in pediatric and young adult patients with BAV using time-resolved three-dimensional phase contrast (4D flow) MRI. The aim of this study is to utilize 4D flow MRI to compare thoracic aorta flow patterns in pediatric and young adult patients with BAV with and without aortic coarctation or coarctation repair. Methods In accordance with an IRB-approved protocol, 17 patients with BAV (age = 11.9 +/- 5.3 years) who underwent cardiovascular MRI including 4D flow as part of follow-up care were included. Seven patients had aortic coarctation including 5 patients with coarctation repairs. Images were processed using in-house software for noise reduction, anti-aliasing, and eddy current correction. Flow visualization and quantification were performed in EnSight (CEI, Apex, NC). Aortic root z-scores were calculated from MRI measurements and height and weight at time of scan in EchoIMS (Merge, Chicago, IL). Flow jet pattern and helicity were assessed in the ascending aorta, aortic arch, and descending aorta. Flow jet pattern was determined by the region of peak velocity in systole corresponding to anatomically designated quadrants of

[Figure][1] [![Graphic][3] ][3] A 9-year-old girl with a history of aortic coarctation, large ventricular septal defect (VSD), patent ductus arteriosus, and bicuspid aortic valve had previously undergone neonatal coarctation repair with ductal ligation followed by VSD closure at 4

Background Single ventricle physiology (SVP) is one of the most severe forms of complex congenital heart disease (CHD). Patients undergo multiple surgical interventions including the Fontan procedure (caval venous return is routed directly to the pulmonary arteries). Despite the apparent success of the procedure, it is unclear why some patients develop ‘failing Fontan physiology’ while others remain asymptomatic. However, there is growing evidence that underlying hemodynamics in the Fontan circulation may