Helical and retrograde secondary flow patterns in the aortic arch studied by three-directional magnetic resonance velocity mapping.

BACKGROUNDHelical and retrograde secondary flows have been recorded in the aorta, but their origins and movements in relation to the arch have not been clarified. We set out to do this using magnetic resonance velocity mapping.METHODS AND RESULTSThree-directional phase contrast cine magnetic resonance velocity mapping was used to map multidirectional flow velocities in the aortas of 10 healthy volunteers. Computer processing was used to visualize flow vector patterns in selected planes. Right-handed helical flows predominated in the upper aortic arch in late systole, being clearly recognizable in 9 of the 10 subjects. Nonaxial components of velocity in this region reached 0.29 m/s (+/- 0.05 m/s) as axial velocities declined from a peak of 1.0 m/s (+/- 0.1 m/s). Helical flow patterns in the upper descending aorta varied between subjects, apparently depending on arch curvature. End-systolic retrograde flow originated from regions of blood with low momentum, usually along inner wall curvatures. Flow studies ...