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Optimisation criterion for pulsatile timing: observation in the human fetus

Gonser, M. and Pahlevan, N. M. and Gharib, M. (2020) Optimisation criterion for pulsatile timing: observation in the human fetus. Ultrasound in Obstetrics and Gynecology, 56 (S1). pp. 197-198. ISSN 0960-7692.

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Objectives: Pulsatile cardiac action is an energy consuming process. During pulse wave (PW) travel to the periphery, reflection back to the LV occurs. The concept of wave condition number, WCN, provides evidence that energy consumption of cardiac action is minimised when time of return Tr to LV takes a certain percentage of the cardiac cycle T. Our objective was to assess WCN and reflection timing Tr/T in the human fetus. Methods: Based on the WCN relation: WCN = HR×L/PWV, energy consumption of pulsatile LV action is optimised for WCN = 0.1 (HR: heart rate, L: effective aortic length, PWV: aortic PW velocity; Pahlevan 2014, 2020). Rearranging with Tr = 2L/PWV (figure) yield Tr/T = 0.2 as optimal reflection timing. To obtain Tr in the fetus by Doppler, hemodynamic modelling is required (figure): PWs arrive twice at cerebral circulation: 1st as a primary wave and 2nd after reflection and return. A systolic shoulder (S) in MCA Doppler (MCA‐S) represents this 2nd impulse and delay δt corresponds to Tr (Mills 1970). Results: Tr data of IUGR fetuses with MCA‐S were obtained by this method (Gonser 2018): Tr = 96 ± 15ms (GA 31 ± 3w). T = 423ms (FHR 140bpm) yield Tr/T = 96ms/423ms = 0.23, showing good agreement with optimal reflection timing of 20%, as suggested by the WCN. Conclusions: In spite of circulatory stress, IUGR fetuses maintain nearly optimal pulsatile timing, probably due to the priority of minimal energy consumption. Thus appearance of MCA‐S is not an artifact, but a sign of nearly optimal timed PW reflection.

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Gharib, M.0000-0002-2204-9302
Additional Information:© The Authors 2020. Issue Online: 15 October 2020; Version of Record online: 15 October 2020; Manuscript accepted: 18 August 2020; Manuscript revised: 09 August 2020; Manuscript received: 19 June 2020.
Issue or Number:S1
Record Number:CaltechAUTHORS:20201019-080247006
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Official Citation:Gonser, M., Pahlevan, N. and Gharib, M. (2020), VP34.06: Optimisation criterion for pulsatile timing: observation in the human fetus. Ultrasound Obstet Gynecol, 56: 197-198. doi:10.1002/uog.22839
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106133
Deposited By: Tony Diaz
Deposited On:20 Oct 2020 16:00
Last Modified:20 Oct 2020 16:00

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