The document summarizes the embryology and fetal circulation of the heart. It describes how the heart develops from a single tube into a four-chambered structure over the first 8 weeks of gestation. During this period, the circulatory system changes from receiving oxygenated blood directly from the placenta to pulmonary circulation after birth. The document then outlines several common congenital cardiac anomalies such as atrial and ventricular septal defects, transposition of the great vessels, and tetralogy of Fallot.

1. EMBRYOLOGY OF HEART
AND FETAL CIRCULATION
Dr.Archana Koshy

2. • Formation of the cardiovascular system begins
during the 3rd week of gestation and is
completed by the end of the 8th week

3. • In the third week of development, the germ disk has the appearance of a flat
oval disk and is composed of two layers: THE EPIBLAST AND THE
HYPOPLAST.
• The first faces the amniotic cavity and the latter faces the yolk sac.
• A prim itive groove, appears at approximately 16 days of development and
extends half the length of the embryo. Serves as a conduit for epiblast cells
that migrate inwards toward the hypoblast and replace it to form the
endoderm

4. EMBRYONIC FOLDING
• The flat germ disk transforms into a tubular structure
during the fourth week of development
• Through a process of differential growth causing the
embryo to fold in two different dimensions:
1. Craniocaudal axis due to the more rapid growth of the
neural tube forming the brain at its cephalic
end. Growth in this direction will cause the embryo
to become convex shaped.
2. Lateral folding causing the two lateral edges of
the germ disk to fold forming a tube-like structure

5. • Prior to embryonic folding, angiogenic cell clusters coalesce
to form capillaries in mesoderm of the germ disk.
• The blood vessels on either side of the neural tube join at
their cranial end.
• As the embryo folds in its lateral dimension, it causes the
embryo to acquire a tubular form
• The two outer endocardial tubes will start fusing cranially to
caudally, thus forming a single median tube—the primitive
heart tube.

7. PRIMITIVE HEART
• The single tubular heart develops many
constrictions outlining future structures.

8. • Looping of the primitive heart occur on approximately day 23
of development .
• As the heart tube loops, the cephalic end of the heart tube
bends ventrally, caudally, and slightly to the right.
• The bulboventricular sulcus becomes visible from the
outside, and from the inside a primitive interventricular
foramen forms.
• The bulbus cordis forms the right arm of the U-shaped heart
tube and the primitive ventricle forms the left arm

13. 1. The atria and inlet portion of the ventricle enlarge and the
AV junction lags behind.
2. The sulcus tissue to invaginate into the ventricular cavity,
forming a hanging flap.
3. The endocardial cushion tissue is located at the tip of this
flap, which is formed from three layers.
4. The inlet portion of the ventricles then becomes
undermined, forming the tethering cords holding the newly
formed valve leaflets.

20. FETAL CIRCULATION

21. • Blood oxygenated in the placenta is returned by the
umbilical veins which enters at the umbilicus and
joins the course of the portal vein .
• DUCTUS VENOSUS - Provides a low resistance
bypass between the Portal vein and Inferior Vena
cava .
- Shunts most of the umbilical venous blood into IVC .
• IVC directly enters the right atrium .

26. KEY POINTS
1. Presence of placental circulation which provides for
the gas exchange in the fetus .
2. Absence of gas exchange in the collapsed lungs
3. DUCTUS VENOSUS
4. Foramen ovale
5. DUCTUS ARTERIOSUS

27. POST NATAL CIRCULATION
• Circulatory adjustments occur immediately
following birth
• Brought about by a shift from placental
dependence for gas exchange in the fetus to
pulmonary exchange in the neonate .
• Loss of placental circulation causes a sudden
reduction of flow through the ductus venosus –
closes off .
• Closure of Foramen ovale

30. NEONATAL CIRCULATION

31. CONGENITAL CARDIAC
ANOMALIES

32. ATRIAL SEPTAL DEFECT
 Communication between
the right and left atria.
 Due to the low pressures
of the atria the lesion is
typically asymptomatic
until adulthood despite 2-4
times the normal
pulmonary blood flow.
 Gradual (high
output) congestive cardiac
failure eventually
develops, usually
becoming symptomatic by
the age of 30.

33. PLAIN FILM (CXR)
CAN BE NORMAL IN EARLY STAGES
WHEN THE ASD IS SMALL
1. SIGNS OF INCREASED
PULMONARY FLOW (SHUNT
VASCULARITY)
• Enlarged pulmonary vessels
• Upper zone vascular
prominence
• Vessels visible to the
periphery of the film
• Eventual signs of pulmonary
arterial hypertension
2. CHAMBER ENLARGEMENT
• Right atrium
• Right ventricle

35. VENTRICULAR SEPTAL DEFECT
• 20%–40%
• Results in an abnormal hemodynamic
communication between the right and left
ventricles, causing a left-to-right shunt.
• A large VSD is easily diagnosed on the four-
chamber view alone.

39. TRANSPOSITION OF THE GREAT
VESSELS
• The most common cyanotic congenital heart lesion
found in neonates, accounts for 5%–7% of
congenital cardiac malformations.
• This malposition, in association with stress-induced
thymic atrophy and hyperinflated lungs, results in
the apparent narrowing of the superior
mediastinum on radiographs.
• Produced by a ventriculoarterial discordance in
which the aorta arises from the morphologic right
ventricle and the pulmonary artery arises from the
morphologic left ventricle.

41. • The volume of the pulmonary flow may be
normal in the first few days after birth, but it
increases with closure of the ductus arteriosus.
• This increase may be mild to severe, depending
on the size of the communication.
• A large communication also leads to
enlargement of the heart unless the shunt is
balanced or impeded by an obstruction of the
pulmonary artery.

44. TOTAL ANOMALOUS PULMONARY
VENOUS RETURN
• Occurs when the pulmonary veins fail to drain into the
left atrium and instead form an aberrant connection
with some other cardiovascular structure.
1. TYPE I(55%)-The anomalous pulmonary veins
terminate at the supracardiac level
2. TYPE II(30%)- involves a pulmonary venous
connection at the cardiac level; join either the
coronary sinus or the right atrium.
3. TYPE III-always accompanied by some degree of
obstructed venous return causes cyanosis early
and severe congestive heart failure
4. Type IV- Anomalous venous connections at two or
more levels.

45. • The structure in which the anomalous vein
terminates appears dilated.
• All the systemic venous and pulmonary venous
blood enters the right atrium .
• The only path for its exit to the left heart is, usually
a large atrial septal defect or patent foramen ovale.
• This right-to-left shunt is essential for survival
• The right heart is prominent in TAPVR because of
the increased flow volume, but the left atrium
remains normal in size.

47. PARTIAL ANOMALOUS PULMONARY
VENOUS RETURN
• Anomalous pulmonary vein that drains any or all of
the lobes of the right lung.
• Scimitar vein curves outward along the right cardiac
border and empties into the inferior vena cava .
• SCIMITAR SYNDROME
(a) Hypoplasia of the right lung with dextroposition of
the heart
(b) Hypoplasia of the right pulmonary artery, and
(c) Anomalous arterial supply of the right lower lobe
from the abdominal aorta.

48. • Many patients with a scimitar vein are asymptomatic and
have a normal or near-normal life span.
• Symptoms generally do not occur unless 50% or more of
the pulmonary flow shifts from the left to the right.

49. ENDOCARDIAL CUSHION DEFECTS(4%)
• Results from interruption
of the normal
development of the
endocardial tissues during
gestation.
• The endocardial cushion
normally forms the lower
portion of the atrial
septum, the upper portion
of the interventricular
septum and the septal
leaflets of the mitral valve
and the tricuspid valve.

50. GOOSE NECK DEFORMITY :
• Deficiency of both the conus and sinus portions of
the interventricular septum, with narrowing of the
left ventricular outflow tract.
•

52. TETRALOGY OF FALLOT( 10%–11%)

53. • Uplifting of the cardiac apex because of right ventricular
hypertrophy and concavity of the main pulmonary artery.
• Pulmonary oligemia
• More severe the obstruction of the right ventricular
outflow tract, the more pronounced that deformity

55. COARCTATION OF AORTA/DUCTUS ARTERIOSUS
• Produced by a deformity of the aortic media and intima, which
causes a prominent posterior infolding of the aortic lumen.
• Occurs at or near the junction of the aortic arch and the
descending thoracic aorta.
• Luminal narrowing in turn obstructs the flow of blood from the
left ventricle.
CLINICAL MANIFESTATIONS
• Congestive heart failure in infancy to hypertension with
differential pressures between the upper and lower extremities
in adulthood.
• TWO TYPES :
1. Localized coarctation –Post ductal ( adult )
2. Tubular hypoplasia- Pre ductal ( infantile )

59. EBSTEIN’S ANOMALY
• Downward displacement of the septal leaflets and
posterior leaflets of the tricuspid valve into the inflow
portion of the right ventricle.
• Results in the formation of a common right
ventriculoatrial chamber and causes tricuspid
regurgitation
• The right atrium becomes enlarged, and a R-L shunt is
seen in most patients.
• Cyanosis is caused primarily by the right-to-left shunt.