doppler use in obstetrics doppler in fetal anemia • during anemia, – the blood viscosity ↓the...
TRANSCRIPT
Doppler Use in Obstetrics
Danny Wu, MBChB FACOGClinical InstructorDivision of Maternal Fetal MedicineObstetrics, Gynecology and Reproductive SciencesUCSF
Outline• Background of Doppler ultrasound• IUGR• Fetal cardiovascular changes by Doppler
– Arterial• Umbilical artery• Middle Cerebral Artery
– Venous• Ductus Venosus
• Fetal Anemia– MCA Doppler
Doppler Ultrasound
Safety in Pregnancy
• Diagnostic ultrasound is safe• Doppler ultrasound diagnostic equipment
has greater time-averaged intensities.• In vitro and animal experiments
– potential bio-effects by thermal, cavitational, or other mechanisms.
• ALARA principle (As Low As Reasonably Achievable)
In-utero Growth Restriction• ACOG defined IUGR as EFW < 10th percentile• 4 million birth per year -- 400,000 babies are
IUGR• Consequences
– At birth and in infancy– Childhood and adult life : Barker Hypothesis
• Risk of hypertension, hypercholesterolemia, coronary heart disease, impaired glucose tolerance and diabetes
• Enormous burden
Not All IUGR Are the Same
• Small for gestational age (SGA)– “constitutionally small”
• Pathologically small – Maternal illness present– Fetal pathology present– No obvious reason
Optimal Timing of Delivery
• Despite over 10000 publications on the topic, confusion remains– Definition– IUGR is not a homogenous group– Mode of testing
• Timing of delivery for early IUGR is highly controversial
Fetal Circulation
Dopplers
placenta
ArterialUmbilical Artery
MCA
VenousUmbilical Vein
Ductus Venosus
Uterine artery
Umbilical Artery Doppler
Doppler waveform represents downstream impedance to flow
Doppler Waveform Analysis
Umbilical artery Doppler• As placental insufficiency worsens,
diastolic flow progressively decreases
Morrow RJ; Adamson SL; Bull SB; Ritchie JW SOAm J Obstet Gynecol 1989 Oct;161(4):1055-60.
Decreased Absent Reversed
30% 70%Abnormal Vasculature
Perinatal Outcomes
• Absent or reversed flow is associated with adverse perinatal outcome
• It may be present for weeks before additional sign of fetal compromise occurs
Doppler in High Risk Pregnancy
• Eleven RCTs involving nearly 7000 women were included
• Reduction in perinatal deaths (OR 0.71)• Fewer inductions of labor (OR 0.83)• Fewer admissions to hospital • No difference fetal distress in labor• No difference caesarean delivery
Cochrane Database Syst Rev. 2000;(2):CD000073
Routine Doppler in Low Risk Pregnancy
• Not Recommended• Five trials were included which recruited
14,338 women• No benefit
Cochrane Database Syst Rev. 2008
PhysiologicalChanges
Increased placental vascular resistance
Shunting to vital organs“Brain-sparing”
Impaired cardiacfunctions
UA S/D increases
MCA P/I decreases
Abnormal venous flow
Doppler Changes
MCA Doppler
Brain Sparing Effect
Cerebral Circulation“Brain Sparing Effect”
Cerebral Blood Flow
• Hypoxemia
• Hypoxemia + Acidemia
MCA Doppler1. Fetus at rest2. Circle of Willis3. Zoom – MCA 50% of
screen4. Sample volume 1mm
placed between origin of carotid and the middle of the artery
5. Angle between USS and blood flow = 0°
6. Consistent waveforms7. Repeat 3 times
Doppler Waveform Analysis
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
Example of an MCA Doppler tracing at 27 weeks
Middle Cerebral ArteryIUGR
MCA PI PO2
MCA PI PO2 2 – 4 SD
MCA PI PO2 < 4 SD
Ductus Venosus
Qualitative Assessmnet
• Blood flow should always be antegrade
• Absent or reversed flow is alwaysabnormal
SD
A
Outcomes related to Doppler changes
Baschat et al Ultrasound Obstet Gynecol 2006; 27: 41–47
Venous Doppler abnormalityis the strongest predictor
38.8%Venous
11.5%AEDF/REDF
5.6%SD elevated
Perinatal MortalityDoppler Abnormality
Baschat.Ultrasound Obstet Gynecol 2004; 23: 111–118
Timing of Delivery
• Abnormal venous Doppler selects out the fetuses that are at highest risk
• Limited options:1) Wait2) Deliver
• Gestational age remains a major factor for adverse perinatal outcome especially in very preterm infants
Baschat et al Obstet Gynecol vol 109 , no.2(1), 2007
Other considerations
• Picconi et al 2008– 19 fetuses with IUGR followed prospectively– 14 fetuses demonstrated intermittent DVRF
with median time to delivery or death in 13 days (1-57 days)
– Among those with continuous : medianinterval of 7 days (1-23 days)
– Cord pH and BE available for 10 fetuse:• Only one had abnormal pH and another one with
BE
Key Points
• Doppler study to characterize fetal cardiovascular changes offer promise when managing early IUGR
• Currently there is no consensus on– What is the best test– When is the best time
MCA Doppler
Peak velocity flow correlates well with fetal anemia
Fetal Anemia
• Causes– Red cell alloimmunization
• eg Anti-D, Anti-Kell, Anti-c – Parvovirus infection – Chronic fetomaternal hemorrhage – Inherited RBC disorders
• eg Alpha Thalassemia
MCA Doppler in Fetal Anemia
• During anemia, – the blood viscosity ↓ the blood velocity ↑
• The correction of the fetal anemia lowers the fetal blood velocity.
Advantage of MCA peak velocity
• Cerebral arteries respond quickly to hypoxemia1
• Easily visualized with 0° angle1
• Low intra-observer and inter-observer variability2
1. Mari G et al Obstet Gynecol 2002; 99:589–5932. Mari G et al Middle cerebral peak systolic velocity:technique and variability. J Ultrasound Med2005; 24:425–430.
MCA Doppler1. Fetus at rest2. Circle of Willis3. Zoom – MCA 50% of
screen4. Sample volume 1mm
placed between origin of carotid and the middle of the artery
5. Angle between USS and blood flow = 0°
6. Consistent waveforms7. Repeat 3 times
MCA PSV and Gestational Age
Mari et al 2000
• 111 fetuses at risk of Rh isoimmunisation vs 265 controls
• MCA-PSV (above 1.5 MoMs) for the prediction of moderate or severe anemia
• Sensitivity was 100% (95% CI 86-100), with a false positive rate of 12%
N Engl J Med 2000; 342:9-14.
Results
MCA Doppler vs Amniocentesis
• Oepkes et al • Multi-centered prospective study• 164 women with Rh(D), Rh(c), Rh(E), and
Fy(a) alloimmunized pregnancies with indirect antiglobulin titers ≥1:64 and antigen positive fetuses
N Engl J Med. 2006 Jul 13;355(2):156-64
Results
81 (72.0-88.0)81 (70.7-88.4)ΔOD450
Queenan’s
77 (67.3-84.0)76* (64.8-84.0)ΔOD450
Liley’s
82 ( 73.3 – 88.9 )88 ( 78.4-93.5 )MCA
Specificity% (CI)
Sensitivity% (CI)
Special Considerations • >35 week
– Higher false positive rate1
• After first transfusion– Useful to time repeat transfusion2
• After 2 transfusions– Correlations remains but data more limited3
1.Zimmerman et al RCOG 2002 Br J Obstet Gynaecol 109, pp. 746–7522.Detti et al AJOG Nov 2001, Pages 1048-1051 3.Mari et al AJOG 2005 Sep;193(3 Pt 2):1117-20
MCA After 1 Transfusion
Correlation after 2 Transfusions
Special Considerations
• Also useful in anemia due to other causes– Congenital parvovirus B19 infection1
– Maternal fetal hemorrhage2
– Twin-to-Twin Transfusion Syndrome3
1 Cosmi et al AJOG 2002 Nov;187(5):1290-3.2 Eichbaum et al Fetal Diagn Ther. 2006;21(4):334-8 3.Senat et al Am J Obstet Gynecol 2003; 189:1320–1324.
ACOG Technical Bulletin
• “ In a center with trained personnel and when the fetus is at an appropriate gestational age, middle cerebral artery Doppler measurements seem to be an appropriate noninvasive means to monitor pregnancies complicated by red cell alloimmunization”
ACOG Technical Bulletin no 75. 2006 Aug;108(2):457-64
Thank You