Fetal physiology and echo Flashcards
What % of combined ventricular output does the RV handle vs the LV?
RV= ~ 60%, LV ~ 30% aka double
What % of combined ventricular output goes through the pulmonary circulation?
7%
What % of combined venticular output goes through the transverse aorta?
Just 10%
What is the function of the foramen ovale?
To shunt oxygenated blood into the left circulation so it can reach the brain and coronaries
Is the fetal circulation a parallel or in series circulation?
Parallel
Umbilical vein:
- Describe anatomy
- Describe normal doppler pattern
Vein brings oxygenated blood from the placenta to the fetal circulation (think of how it is in the venous circulation for the baby, but how the oxygenation is different d/t placenta)
Normal doppler pattern is a low velocity, non-pulsatile pattern
Describe abnormal doppler patterns in the umbilical vein
Progression from single pulsation to double pulsation (progressive risk of mortality)
Ductus venosus
- Describe anatomy
- Describe the normal doppler pattern
Bypasses the hepatic circulation so that oxygenated blood is preserved when entering the heart. Can see on echo via aliasing in the liver.
Normal doppler pattern may have some pulsatility due to sphincter (more so than the UV) but is also mostly continuous, low velocity
Describe abnormal doppler patterns in the ductus venosus
1) reduced, absent or reversal of flow
2) abnormalities in velocity and pulsatility index
What is reversal of flow in the ductus venosus doppler associated with?
Right sided heart disease such as tricuspid valve abnormalities or pulmonary abnormalities that alter the pressure in the RA
How do you calculate combined ventricular output in a fetal echo?
Output across valve = Valve area x fetal HR x VTI
Then add the two outputs together
What physiologic changes may account for gradual increase in combined ventricular output in fetus over time?
1) Increased ventricular compliance increasing SV
2) Decreased peripheral vascular resistance decreasing afterload
What is a normal combined ventricular output in a fetus?
420-450 ml/kg/min
What disease state can restriction or PFO closure result in?
Right heart CHF - ventricular hypertrophy, dilation, tricuspid regurgitation, etc.
Describe the typical doppler pattern through a PFO
Right to left, laminar flow
What disease processes can result in reduced or reversal of flow (L->R) through the fetal PFO?
Processes that increase left sided pressures, such as MV disease or HLHS or coarctation
Describe pulmonary vein doppler patterns
Forward flow in systole and diastole, may get some cessation of flow or reversal at atrial systole
What disease state can premature closure of the ductus result in?
RV pressure overload, hydrops, fetal death
What does a normal middle cerebral artery doppler look like?
Pulsatile with reduction in velocity during diastole but does not go to zero or reverse
What may an increase in peak systolic velocity in the MCA represent?
Fetal anemia with increased CO
What may blunting of the pulsatility of the MCA via doppler represent?
Problems with blood flow to fetus resulting in cerebral vasodilation
What may increased pulsatility in the MCA via doppler represent? What would this look like on doppler?
Right sided obstruction lesions with ductal run off from the aorta into the pulmonary arteries
Would look like sharp narrow peaks
What does a normal umbilical artery doppler look like? What may cause abnormalities?
Normal doppler looks alot like aortic doppler with pulsatile antegrade flow during systole and diastole
Abnormalities usually reflective of changes in fetal peripheral resistance or systemic resistance - placental issues
Most common indication for fetal echo?
Abnormal screening ultrasound by OB (40-50% will actually have disease)
