Altered 4-D magnetic resonance imaging flow characteristics in complex congenital aortic arch repair.

BACKGROUND: Interrupted aortic arch (IAA) is a rare but severe congenital abnormality often associated with bicuspid aortic valve (BAV). Complex re-interventions are often needed despite surgical advances, but the impact of aortic hemodynamics in repaired patients is unknown. OBJECTIVE: Investigate effect of IAA repairs on aortic hemodynamics, wall shear stress and flow derangements via 4-D flow MRI. MATERIALS AND METHODS: We retrospectively analyzed age- and gender-matched cohorts (IAA [n=6], BAV alone [n=6], controls [n=6]) undergoing cardiac MRI including 4-D flow. Aortic dimensions were measured from standard MR angiography. We quantified peak systolic velocities, regurgitant fractions and wall shear stress in the ascending aorta (AAo), transverse arch and descending aorta (DAo) from 4-D flow, and we graded helix/vortex flow patterns from 3-D blood flow visualization. RESULTS: Children and young adults with IAA had a wide range of arch dimensions, peak systolic velocities, regurgitant fractions and flow grades. Peak transverse arch systolic velocities were higher in patients with IAA versus controls (P=0.02). Flow derangements in the AAo were found in patients with IAA (median grade=2, 5/6 patients, P=0.04) and BAV (median grade=3, 5/6 patients, P=0.03) versus controls. Flow derangements in the DAo were only seen in patients with IAA (median grade=1, 5/6 patients, P=0.04), and 5/6 people with IAA had helical flow in head and neck vessels. Wall shear stress was increased in people with IAA along the superior transverse arch and proximal DAo versus controls (P=0.02). CONCLUSION: Complex congenital aortic arch repairs can change aortic hemodynamics. Associated cardiac defects can further alter findings. Studies are warranted to investigate clinical implications in larger cohorts.