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. 2021 Jun 9;107(1):65–69. doi: 10.1136/archdischild-2020-321431

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© Author(s) (or their employer(s)) 2022. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

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Cross section of the hepatic vein over time using colour Doppler M-mode. Blood flow direction alternates between antegrade (blue) and retrograde (red) with a high frequency and corresponding ECG signal.