Fetal Circulation

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Fetal Circulation Adaptation

• Primitive heart starts beating at about 4 weeks
• Circulatory system of fetus established between
  8-12 weeks
• Fetus develops its own blood
• no mixing with mothers

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Fetal Circulation Adaptation

• Lungs only receive a tiny proportion of fetal
  blood
• Placenta carries out respiration
• ? Normal function of lungs is not required!

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Fetal Circulation
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Fetal Circulation
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Fetal Circulation
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Fetal Circulation Adaptation

• Transitional Changes
• Changes in ductal flow
• ?Pulmonary vascular resistance
• ?Systemic vascular resistance

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Fetal Circulation Adaptation

• Transition may take upto 48 hours.
• Consequences
• Innocent heart murmurs- due to transitional
  changes
• CHD having normal heart sounds in early hours,
  followed by collapse when transitional changes
  complete

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Fetal Circulation Adaptation

• Documentation - normal heart sounds at time of
  auscultation!
• Education- mothers to be aware of normal
  behaviour
• Seek advice when deviates from norm

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Heart Sounds

• They are basically the result of
• opening and closing of the heart valves
• vibration of blood against the heart and
  vessel walls

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Heart Sounds

• Most obvious of heart sounds are the first and
  second heart sounds
• S1 and S2
• Demarcates systole from diastole

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S1 first heart sound (lub)

• signifies the beginning of systole
• produced by closure of the AV valves
• (mitral tricuspid)
• Why?
• ? pressure in ventricles exceeds that in atria

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S2 second heart sound (dub)
Towards end of systole -    corresponds with
closure of the semilunar valves (aortic
pulmonary) Physiologically split sound Why?
Aortic valve closes slightly before pulmonic
valve (0.03-0.05 sec.)
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Heart Sounds

• How to distinguish between S1 S2
• Diastole takes about twice as long as systole
• ?longer pause between S2 S1 than S1 S2

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Heart Sounds

• Rapid heart rate (neonates) difficult to discern
  between S1 S2
• Palpate radial pulse when auscultating.
• Heart sound heard when first felt pulse is S1
• When pulse disappears, is S2

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Heart Murmurs
Caused by turbulent blood flow Most murmurs occur
during systole between SI and S2. Diastolic
murmurs are audible between S2 and S1 An echo is
usually carried out when a murmur is heard
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Heart Murmurs

• What causes murmurs in neonates?
• Consider transitions at birth!

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PDA

• Harsh, continuous rolling thunder murmur
• Localised -2nd L. intercostal space
• May radiate to L. clavicle/L. sternal border
• Bounding pulses

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Why is PDA a concern?
DA stays open ? oxygen-rich blood passes from the
aorta to the pulmonary artery Mixes with the
oxygen-poor blood already flowing to the
lungs.
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PDA
The blood vessels in the lungs have to handle a
larger amount of blood than normal. Bigger the
PDA-larger the amount of blood to lungs ? Higher
the pressure!
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PDA
Without medical treatment - blood vessels in the
lungs become diseased by the extra pressure.
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PDA
Because blood is pumped at high pressure through
the PDA ? the lining of the
pulmonary artery becomes irritated and inflamed.
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PDA
Bacteria in the bloodstream can infect this
injured area ? bacterial endocarditis
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Ventricular Septal Defects

• the most commonly occurring type of
  congenital heart defect
• occurs in 1-3 out of every 1,000 live
  births
• 4-7 out of every 1,000 premature births.

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VSD

• A loud harsh , blowing murmur
• Localised in lower left sternal border
• - Usually on 2nd or 3rd day

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Ventricular Septal Defects
Small VSD - a small amount of blood passes
through from the LV to RV. Large VSD - more
blood passes through and mixes with the normal
blood flow in the right heart.
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Ventricular Septal Defects
Extra blood causes higher pressure in the blood
vessels in the lungs. ? The larger the volume
of blood that goes to the lungs, the higher the
pressure.
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Ventricular Septal Defects
The lungs - able to cope with this extra
pressure for while. After a while, the blood
vessels in lungs become diseased by the extra
pressure
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Ventricular Septal Defects

• Pressure ? in the lungs
• Blood flow from the LV through the VSD into
  the RV gradually reduces
• Blood flow to the lungs will also diminish.
• Temporary relief only!

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VSD
Blood normally flows from areas of high
pressure to areas of low pressure. ? Eventually
pressure in the right side of the heart will
exceed pressure in the left. Oxygen-poor blood
flows from the RV, through the VSD, into the LV
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VSD
The body does not receive enough oxygen in the
bloodstream to meet its needs Tissue damage also
eventually occurs in the RV ? Bacterial
infection ? bacterial endocarditis
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Ventricular Septal Defects
Diagnosis? - a heart murmur - a noise caused by
the turbulence of blood flowing through the
opening from the left side of the heart to the
right.
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Coarctation of the Aorta

• Heard loudest in the back
• May detect absent femoral pulses

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Assessment of CVS

• HISTORY
• Maternal CHD - 10-15 risk in neonate
• Maternal diabetes - x3-4 risk than gen. pop

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Assessment of CVS

• Observe activity, tone
• ? passsively flexed ? flaccid
• Colour
• centrally pink, ? mottled ? Cyanosed
• ? Plethoric
• Capillary filling time not more than 3
• seconds

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Assessment of CVS

• Pulses-Femoral brachial
• - rate/rhythm/volume
• - absent/weak/bounding (PDA)

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Assessment of CVS

• HISTORY
• Observe activity/tone/colour
• Feeding pattern
• Auscultation
• Check femoral /brachial pulses
• Assess pulse volume
• Check capillary refill time (2 seconds)