This document discusses congenital heart diseases (CHDs), which are abnormalities of the heart or blood vessels present from birth. CHDs result from faulty development of cardiovascular structures during weeks 3-8 of gestation. The document covers cardiac development, pathogenesis of CHDs, classification of CHDs into cyanotic and non-cyanotic types, clinical presentations of common CHDs like atrial septal defect and ventricular septal defect, and cyanotic CHDs such as tetralogy of Fallot. Common CHDs are described in detail, including abnormal blood flow patterns, clinical findings, and treatments.

1. Congenital Heart Diseases
Basant Raj Joshi
Bibek Ghimire
PAHS SOM Third Batch
Junior Clerkship-Pediatrics
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2. Congenital Heart Disease
• General term used to describe abnormalities of Heart or Great
Vessels that are present from birth.
• This results due to faulty embryogenesis during gestational
weeks 3-8. (This is when major cardiovascular structures form
and begin to function)
• Most severe anomalies are incompatible even to intrauterine
life.
• If they are compatible till embryologic maturation and birth;
only individual chambers or discrete regions of heart are
affected.
• Remainder of the heart develops relatively normally.
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3. Human Cardiac Development
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4. 18December2015
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5. Development of Heart
• Both heart fields contain multipotent progenitor cells for all
major cell types of heart.
• Endocardium
• Myocardium
• Smooth muscle
• Even at this early stage, each heart field is destined to give rise
to particular portions of the heart.
• First heart field: left ventricle
• Second heart field: outflow tract, right ventricle and most of the
atria.
• Neural crest cells migration into the outflow tract and septation
of atrial chambers
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6. Pathogenesis
• Proper orchestration and transformation of these cells into
different structure depends upon different transcription factors
mediated by various signaling molecules.
• Hemodynamic forces also play vital role in development of
cardiac structures.
• Many genetic defects can lead to cardiac malformations and
many of them are autosomal dominant
• Cause partial loss of one or another transcription factors
• These include
• Single gene mutations
• Small chromosomal deletions
• Additions or deletions of whole chromosomes(trisomies or
monosomies) e.g., trisomy 21
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8. 3 major categories of CHD.
• Malformations causing a left-to-right shunt
• Malformations causing a right-to-left
• Malformations causing an obstruction
• Shunt = abnormal communication between chambers or blood
vessels.
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9. Classification of CHD
Non-cyanotic Cyanotic
With shunts With shunts
Atrial septal defect
Ventricular septal defect
Patent ductus arteriosus
Partial anomalous venous drainage
Fallot’s tetralogy
Transposition of the great vessels
Severe Ebstein’s anomaly
Without shunts Without shunts
Coarction of the aorta
Congenital aortic stenosis
Severe pulmonary stenosis
Tricuspid atresia
Pulmonary atresia
Hypoplastic left heart
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10. NADA’s Criteria
Major
• Systolic murmur Grade III
or more
• Diastolic murmer
• Cyanosis
• CCF
Minor
• Systolic murmur grade <
III
• Abnormal second sound
• Abnormal ECG
• Abnormal X-rays
• Abnormal BP
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Presence of 1 major or 2 minor are essential for diagnosis of CHD

11. Incidence
• Approximately 1% (estimates range from 4 to 50 per 1000 live
births)
• Most common type of heart disease among children
• Incidence higher in premature infants and in stillborns.
• Approximately half of the congenital cardiovascular
malformations are diagnosed in the first year of life but some
mild forms may not become evident until adulthood. E.g., ASD
 40-50% in 1 week of age
 50-60% 1 month of age
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12. 18December2015
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13. What determines the direction of
blood flow through a shunt?
• Blood flows from high pressure chamber to low pressure
chamber
• Chamber pressure is determined by downstream resistance
• After birth, pulmonary vascular resistance is much lower than
systemic vascular resistance
• RV pressure ~ 25/5 mm Hg
• LV pressure ~ 120/10 mm Hg
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14. Which way does blood flow?
• Atrial septal defect: Blood flows from left atrium to right
atrium
• Ventricular septal defect: Blood flows from left ventricle to
right ventricle
• Patent ductus arteriosus: Blood flows from descending aorta
into main pulmonary artery
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15. Consequences of shunts (abnormal
mixing of blood)
• Causes volume overload of affected chambers
• Problems with oxygenation:
• Hemoglobin O2 saturation
Normal Left to right
shunt
Right to left
shunt
Aorta 95-100% 95-100% 80-85%
Pulmonary
artery
75% 80-85% 60-65%
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16. Atrial septal defect
• Normally, in the fetus,
blood flows from
right atrium through
patent foramen ovale
into the left atrium
• After birth, the
septum primum and
secundum fuse and
there is no more
communication
between the atria
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17. Amount of shunting through atrial septal defect
• Depends on size of ASD
1.5 cm diameter hole
• With large ASD, pressures
in RA and LA are equal
but flow is from LA to RA
because of lower
pulmonary vascular
resistance and greater
compliance of RV
• Dilated RA, RV, PA, LA
• Normal arterial
hemoglobin O2 saturation
and high hemoglobin O2
saturation in PA
10
10 120/10
40/10
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18. Atrial septal defect: Clinical presentations
• Increased respiratory infections because of increased
pulmonary blood flow
• Shortness of breath with exertion because of increased
blood flow through lungs and stiffer lungs
• Atrial rhythm problems because of atrial enlargement
• Flow through the atrial septal defect does not cause a
murmur because there is a large hole with equal pressures
in RA and LA (flow through ASD is not turbulent)
• Usually there is a pulmonary flow murmur because of
increased flow through the normal pulmonary valve
• Treatment = closure of ASD to prevent heart failure
• Can be surgical or with device to plug hole
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19. Ventricular septal defect
• Location:
Membranous VSD
(70%) and muscular
VSD (20%)
• Shunt from LV into
RV –PA-lungs-LA
after pulmonary
vascular resistance
falls following birth
• Dilated PA, LA and
LV
• RV is not dilated
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20. VSD: clinical presentation
• Large VSD may cause heart failure in infancy because of high
shunt flow
• pulmonary flow >>systemic flow
• VSD often closes spontaneously
• Large VSDs require surgery
• Even a small VSD causes loud systolic murmur because of big
pressure difference between LV and RV in systole (120-25 =
95 mm Hg)
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21. Complication of large, uncorrected VSD
• Increased pulmonary blood
flow over several years at
high pressure, leads to
thickening of the walls of
pulmonary arterioles and
development of severe
irreversible pulmonary
hypertension.
• The left to right shunt then
becomes a right to left shunt
and results in arterial
hypoxemia and cyanosis
• This is called Eisenmenger’s
syndrome.
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22. Patent ductus arteriosus
• Failure of ductus
arteriosus to close after
birth
• More common if birth at
high altitude, maternal
rubella infection,
premature baby
• Blood flow from
descending aorta into
pulmonary artery
• Which chambers
will be enlarged?
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23. Patent ductus arteriosus
• Increased pulmonary
blood flow, dilated left
atrium, left ventricle
• Systolic and diastolic
murmur because of
continuous flow from
aorta to pulmonary artery
throughout the cardiac
cycle
• May result in
Eisenmenger’s syndrome
if not corrected (high
pulmonary vascular
resistance with right to
left shunt)
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24. Cyanotic Congenital Heart Disease
• When blood from the right side of the circulation flows
directly into the left side (right-to-left shunt); hypoxemia and
cyanosis results because of admixture of poorly oxygenated
venous blood with systemic arterial blood.
• So, right-to-left shunts are called as cyanotic congenital heart
disease.
• Most important of them are:
1. Tetralogy of Fallot
2. Transposition of great arteries
3. Persistent truncus arteriosus
4. Tricuspid atresia
5. Total anomalous pulmonary venous connection
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25. Tetralogy of Fallot
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26. Tetralogy of Fallot
• Loud systolic murmur because of pulmonic/RV infundibular
stenosis
• VSD is large—laminar flow therefore no murmur
• Treatment is surgical repair with VSD closure and resection of
infundibular/pulmonic valve stenosis
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