Heart Embryology and the defect that may happen during development

1. Heart Defects
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2. Heart Defects - 1
• Heart and vascular abnormalities make up the
largest category of human birth defects.
• Genetic factors
• Environmental agents
• Both (multifactorial causes)
• Cardiovascular teratogens include rubella
virus and thalidomide. Others include retinoic
acid (Accutane), alcohol.
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3. Heart Defects - 2
• Atrial Septal Defect
• Tricuspid atresia
• Ebstein anomaly
• Ventricular septal defects (VSDs)
• Persistent truncus arteriosus
• Transposition of the great vessels
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4. Atrial septal defect (ASD)
• A congenital heart abnormality with an
incidence of 6.4/10,000 births.
• 2:1 prevalence in female to male infants.
• Most significant defects is the:
• Ostium secundum defect.
• Persistent atrioventricular canal
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5. • A. Normal atrial septum formation.
• B,C. Ostium secundum defect caused by excessive resorption of the septum
primum.
• D,E. Similar defect caused by failure of development of the septum secundum.
• F. Common atrium, or cor triloculare biventriculare, resulting from complete failure
of the septum primum and septum secundum to form. 5

6. Persistent atrioventricular canal
• Endocardial cushions : Structures consisting of
loose connective tissue covered by endothelium
that are responsible for most septation processes
occurring in the heart.
• Divide the canal into a right and left orifice.
• Participate in formation of the membranous
portion of the interventricular septum and in
closure of the ostium primum.
• Persistent atrioventricular canal happens when
Endocardial cushions fail to fuse.
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7. • A. Persistent common
atrioventricular canal.
This abnormality is
always accompanied by
a septum defect in the
atrial as well as in the
ventricular portion of
the cardiac partitions.
• B. Valves in the
atrioventricular orifices
under normal
conditions.
• C. Split valves in a
persistent
atrioventricular canal.
• D,E. Ostium primum
defect caused by
incomplete fusion of
the atrioventricular
endocardial cushions. 7

8. Tricuspid atresia
• Obliteration of the right atrioventricular orifice.
• characterized by the absence or fusion of the
tricuspid valves.
• Always associated with
• (a) patency of the oval foramen
• (b) ventricular septal defect
• (c) underdevelopment of the right ventricle
• (d) hypertrophy of the left ventricle.
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9. • A. Normal heart.
• B. Tricuspid atresia. Note the small right ventricle and
the large left ventricle. 9

10. Ventricular septal defects (VSDs)
• Involves the membranous or muscular portion
of the septum.
• Most common congenital cardiac
malformation (12/10,000 births)
• Often associated with abnormalities in
partitioning of the conotruncal region
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11. • A. Normal heart.
• B. Isolated defect in the membranous portion of
the interventricular septum. Blood from the left
ventricle flows to the right through the
interventricular foramen (arrows). 11

12. Tetralogy of Fallot
• Most frequently occurring abnormality of the
conotruncal region.
• Due to an unequal division of the conus resulting from
anterior displacement of the conotruncal septum
• produces four cardiovascular alterations:
• (a) pulmonary infundibular stenosis
• (b) a large defect of the interventricular septum;
• (c) an overriding aorta that arises directly above the
septal defect
• (d) hypertrophy of the right ventricular wall because of
higher pressure on the right side.
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13. • A. Surface view.
• B. The four components of the defect: pulmonary
stenosis, overriding aorta, interventricular septal
defect, and hypertrophy of the right ventricle.
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14. Persistent truncus arteriosus
• Results when the conotruncal ridges fail to
fuse and to descend toward the ventricles
• Occurs in 0.8/10,000 births
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15. • The pulmonary artery originates from a common
truncus (A).
• The septum in the truncus and conus has failed to
form (B).
• This abnormality is always accompanied by an
interventricular septal defect. 15

16. Transposition of the great vessels
• Occurs when the conotruncal septum fails to
follow its normal spiral course and runs straight
down.
• As a consequence, the aorta originates from the
right ventricle, and the pulmonary artery
originates from the left ventricle.
• Occurs in 4.8/10,000 births
• Sometimes is associated with a defect in the
membranous part of the interventricular septum.
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17. • A. Transposition of the great vessels.
• B. Pulmonary valvular atresia with a normal aortic
root. The only access route to the lungs is by way of
a patent ductus arteriosus. 17

18. • A. Aortic valvular stenosis.
• B. Aortic valvular atresia. Arrow in the arch of the
aorta indicates direction of blood flow. The
coronary arteries are supplied by this retroflux.
Note the small left ventricle and the large right
ventricle. 18

19. Valvular stenosis
• Valvular stenosis of Pulmonary artery or aorta
occurs when the semilunar valves are fused
for a variable distance.
• Similair incidence for both, occurs in 3 to
4/10,000 births.
• Valvular stenosis of the pulmonary artery: the
trunk of the pulmonary artery is narrow or
even atretic.
• Aortic valvular stenosis
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20. Some other defects
• DiGeorge sequence: characterized by a
pattern of malformations that have their
origin in abnormal neural crest development.
• Ectopia cordis: a rare anomaly in which the
heart lies on the surface of the chest.
• Ebstein anomaly: a condition where the
tricuspid valve is displaced toward the apex of
the right ventricle.
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