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Discordant blood flow velocity waveforms in left and right brachial arteries in growth-retarded fetuses
W Sepulveda1, S Bower, P Nicolaidis
1Centre for Fetal Care, Royal Postgraduate Medical School, London, United Kingdom.
Insights
Fetal hypoxemia causes discordant blood flow in upper limb arteries, indicating altered circulation during growth restriction. This "brain-sparing" effect impacts brachial artery hemodynamics, suggesting complex fetal circulatory responses.
Area of Science:
- Fetal Medicine
- Cardiovascular Physiology
- Neonatal Circulation
Background:
- Fetal hypoxemia can trigger a "brain-sparing" effect, prioritizing blood flow to the brain.
- Understanding circulatory adaptations in fetal growth restriction is crucial for perinatal care.
Purpose of the Study:
- To investigate the relationship between the "brain-sparing" effect and upper extremity hemodynamics in fetuses with hypoxemia.
- To determine if fetal hypoxemia leads to discordant blood flow patterns in the brachial arteries.
Main Methods:
- Studied 12 fetuses with severe growth retardation and abnormal umbilical artery Doppler, alongside 12 controls.
- Utilized high-resolution color Doppler ultrasonography to measure pulsatility index (PI) in both right and left brachial arteries.
- Compared brachial artery impedance indices between growth-retarded and control fetuses.
Main Results:
- Growth-retarded fetuses exhibited significantly lower impedance indices in the right brachial artery compared to the left (mean delta PI 1.0, P < .001).
- Control fetuses showed no significant difference in brachial artery impedance indices between the right and left sides (mean delta PI 0.0).
- These findings demonstrate discordant hemodynamics in the upper extremities of fetuses experiencing growth restriction and cerebral vasodilation.
Conclusions:
- Discordant left and right brachial artery blood flow velocity waveforms are observed in fetuses with growth retardation and cerebral vasodilation.
- This discordance may result from increased blood flow to the brachiocephalic circulation or altered distribution of ventricular output.
- These hemodynamic changes reflect complex adaptive responses to fetal hypoxemia within the fetal circulatory system.
Objective:
To determine if the increase in cerebral blood flow ("brain-sparing" effect) with fetal hypoxemia is associated with discordant hemodynamics in the upper extremities.
Methods:
We studied 12 fetuses with severe growth retardation, absent or reverse end-diastolic blood flow in the umbilical artery, and low pulsatility index (PI) in the middle cerebral artery, and 12 appropriately grown control fetuses with normal fetoplacental Doppler studies. The right and left brachial arteries were identified by high-resolution color Doppler ultrasonography, and the PI was measured in each brachial artery.
Results:
All growth-retarded fetuses had lower impedance indices in the right than in the left brachial artery (mean delta PI 1.0, 95% confidence interval [CI] 0.7-1.3, P < .001). No differences in the brachial artery impedance indices were found in control fetuses matched for gestational age (mean delta PI 0.0, 95% CI -0.2 to 0.2).
Conclusions:
Left and right brachial artery blood flow velocity waveforms are discordant in fetuses with growth retardation and cerebral vasodilation. Because the right arm receives its blood supply from the same source as the brain (brachiocephalic artery) and given the proximity of the left subclavian artery to the ductus arteriosus, we speculate that this might be the result of increased blood flow into the brachiocephalic circulation and/or functional differences in the distribution of left and right ventricular output within the aortic arch in response to fetal hypoxemia.