The document discusses ductus arteriosus dependent pulmonary blood flow. It describes how the ductus arteriosus normally carries blood from the pulmonary artery to the aorta in fetuses, but closes after birth. If closure causes a significant decrease in pulmonary circulation, the condition is called ductus dependent pulmonary blood flow. Three conditions are described where pulmonary blood flow depends on a patent ductus arteriosus: pulmonary atresia, severe pulmonary stenosis, and tetralogy of Fallot with severe pulmonary stenosis. All three involve obstruction of pulmonary flow that leads to increased right heart pressures and cyanosis without ductal patency.

1. 11) PATHOPHYSIOLOGY OF
DUCTAL DEPENDANT FOR
PULMONARY CIRCULATION CHD

2. Anatomy of Ductus Arteriosus
Connects the main
pulmonary artery to
descending aorta.

3. Physiology of Ductus Arteriosus
• Carries 60% of combined
vent. Output
• Diverts blood from high
resistance pulmonary
circulation to low resistance
descending aorta and
placental circulation.
• PGE1 and PGI2 formed
intramurally and in placenta
maintain ductal patency
in fetal life

4. Post Natal Closure of PDA
• Functional closure
In 12 hr., contraction of
medial smooth muscles
due to ↑ PO2 & ↓ PGE1.
• Anatomical closure
In 3 wk., replacement of
muscle fibres with fibrosis
creating ligamentum arteriosus.

5. • If ductal closure causes significant decrease in
systemic circulation, the condition is called
ductus dependent systemic blood flow
• If ductal closure causes significant decrease in
pulmonary circulation, the condition is called
ductus dependent pulmonary blood flow
BEFORE
BIRTH
AFTER
BIRTH

6. DUCTUS ARTERIOSUS
DEPENDENT
SYSTEMIC BLOOD
FLOW
PULMONARY
BLOOD FLOW
Lesions characterized by the
entire or part of
the systemic blood flow
depends solely on
the patency of the ductus
arteriosus.
– Coarctation of Aorta
(severe)
– Interrupted Aortic Arch
– Hypoplastic Left Heart
Hypoxic lesions characterized
by the pulmonary blood flow
depends solely on
the patency of the ductus
arteriosus.
– Pulmonary atresia
– Severe pulmonary
stenosis
– TOF with severe
pulmonary stenosis

7. DUCTUS ARTERIOSUS
DEPENDENT
PULMONARY BLOOD FLOW

8. I) PULMONARY ATRESIA
• Congenital malformation
of the pulmonary
valve in which the valve
orifice fails to develop.
• The valve is completely
closed thereby
obstructing the outflow
of blood from the heart
to the lungs

9. II) SEVERE PULMONARY STENOSIS
• Is a dynamic or fixed
obstruction of flow from
the right ventricle of the
heart to the pulmonary
artery.
• Usually due to isolated
valvular obstruction
(Pulmonary valve
stenosis), but may be due
to subvalvular or
supravalvular
obstruction.

10. III)TOF WITH SEVERE PULMONARY
STENOSIS
• Large VSD
• Overriding of the
aorta
• **Pulmonary stenosis
• RVH

11. ***OBSTRUCTION OF
PULMONARY FLOW
RVH
RIGHT ATRIAL PRESSURE ↑
SYSTEMIC CYANOSIS
PERSISTENT OPENING
FORAMEN OVALE
Resistance Blood Flow
Fails
Shunting of unoxygenated blood from
the right atrium into the left atrium

12. PDA
LEFT
VENTRICLE
AORTA
PULMONARY
ARTERY