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. 2022 Jan 10;9(2):1118–1126. doi: 10.1002/ehf2.13780

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© 2022 The Authors. ESC Heart Failure published by John Wiley & Sons Ltd on behalf of European Society of Cardiology.

This is an open access article under the terms of the http://creativecommons.org/licenses/by-nc-nd/4.0/ License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non‐commercial and no modifications or adaptations are made.

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Caval flow regulation natural phenomenon (CFRNP) or dynamic stenosis of the IVC. (A) Normal IVC in long‐axis view. (B) Abnormal IVC and dynamic restriction of the IVC flow. (C) Echo image showing IVC dynamic stenosis in expiration; the flow velocity is 1.8 m/s, which corresponds to 13.8 mmHg gradient. (D) Echo image showing IVC dynamic stenosis during inspiration; the flow velocity is 2.08 m/s, which corresponds to 17.3 mmHg gradient. (E) Important features of caval stenosis. (F) Schematic representation of the dynamic stenosis of the IVC.