Peak Systolic Blood Flow in the MCA

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Expected Peak Velocity of Systolic Blood Flow in
the Middle Cerebral Artery (MCA) as a Function of Gestational Age

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Calculations
The Median Peak Systolic Velocity for this age is
Your measurement is Multiples of Median

The risk of anemia is highest in fetuses with a pre-transfusion peak systolic velocity of 1.5 times the median or higher.

Formula: MCA-PSV= e ^{(2.31 + 0.046 GA)}, where MCA-PSV is the peak systolic velocity in the middle cerebral artery and GA is gestational age

In fetuses with anemia the MCA PSV appears to increase above the normal range because of decreased blood viscosity and increased cardiac output associated with the anemia. Single measurements of the MCA PSV blood flow have been found to predict the presence of moderate or severe anemia in fetuses with a sensitivity of 100 percent and a false positive rate of 12 percent with the number of false positive results increased after 35 weeks gestation. Reference ranges of singletons are suitable to assess fetal anemia in monochorionic diamniotic twin pregnancies between 18 and 37 weeks of gestation.

The MCA PSV may used to evaluate anemia in fetuses affected by red blood cell alloimmunization, twin to twin transfusion, twin anemia-polycythemia sequence, alpha-thalassemia, parvovirus , fetomaternal hemorrhage , G6PD deficiency, placental chorioangioma, and other suspected causes of fetal anemia.

It is important that the gestational age be accurately determined since the middle cerebral artery (MCA) peak systolic velocity (PSV) naturally increases with gestational age.

Technique

The fetus should be at rest with no movements or breathing

Obtain an axial section of the fetal head . Image the Circle of Willis using color Doppler (Image A)

Visualize the entire length of the MCA and enlarge the area of the MCA so that it occupies 50% or more of the screen (Image B).

Superimpose the sample volume (1 mm) on the MCA 2 mm after its origin from the internal carotid artery

The ultrasound beam should be parallel to the direction of blood flow . The angle between the ultrasound beam and direction of blood flow should be zero degrees.

The highest peak systolic velocity is measured.

The measurement is taken at least 3 times

By Mark Curran, MD FACOG Updated 4/20/2021

REFERENCES

1.Mari G, Deter RL, Carpenter RL, Rahman F, Zimmerman R, Moise KJ Jr, Dorman KF, Ludomirsky A, Gonzalez R, Gomez R, Oz U, Detti L, Copel JA, Bahado-Singh R, Berry S, Martinez-Poyer J, Blackwell SC. Noninvasive diagnosis by Doppler ultrasonography of fetal anemia due to maternal red-cell alloimmunization. Collaborative Group for Doppler Assessment of the Blood Velocity in Anemic Fetuses. N Engl J Med. 2000 Jan 6;342(1):9-14. doi: 10.1056/NEJM200001063420102. PMID:10620643
2. Society for Maternal-Fetal Medicine (SMFM). Mari G, Norton ME, Stone J, Berghella V, Sciscione AC, Tate D, Schenone MH. Society for Maternal-Fetal Medicine (SMFM) Clinical Guideline #8: the fetus at risk for anemia--diagnosis and management. Am J Obstet Gynecol. 2015 Jun;212(6):697-710. PMID:25824811
3.Cerebral Blood Flow Velocity Waveforms: Clinical Application Detti L, Segata Mmaria, Mari G, In Maulik Dev et al ed: Doppler Ultrasound in Obstetrics and Gynecology , 2nd ed. New York.: Springer 2005 pp 206
4. Delle Chiaie L, et al., Prediction of fetal anemia with Doppler measurement of the middle cerebral artery peak systolic velocity in pregnancies complicated by maternal blood group alloimmunization or parvovirus B19 infection. Ultrasound Obstet Gynecol. 2001;18:232-6. PMID:11555452
5. Mari G, Abuhamad AZ, Cosmi E, Segata M, Altaye M, Akiyama M. Middle cerebral artery peak systolic velocity: technique and variability. J Ultrasound Med. 2005 Apr;24(4):425-30. doi: 10.7863/jum.2005.24.4.425. PMID:15784760.
6. Klaritsch P, Deprest J, Van Mieghem T, Gucciardo L, Doné E, Jani J, Lewi P, Rasmussen S, Lewi L. Reference ranges for middle cerebral artery peak systolic velocity in monochorionic diamniotic twins: a longitudinal study. Ultrasound Obstet Gynecol. 2009 Aug;34(2):149-54. doi: 10.1002/uog.6436. PMID:19644951
7. Picklesimer AH, Oepkes D, Moise KJ Jr, Kush ML, Weiner CP, Harman CR, Baschat AA. Determinants of the middle cerebral artery peak systolic velocity in the human fetus. Am J Obstet Gynecol. 2007 Nov;197(5):526.e1-4. doi: 10.1016/j.ajog.2007.04.002. PMID:17980196

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