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L2. Patent Ductus Arteriosus (PDA)
PDA represent approximately 5-10% of CHD (excluding premature infants).
Etiology: Ductus arteriosus allow blood flow from the pulmonary artery to the aorta
during fetal life. Failure of normal closure of this vessel result in PDA. With falling of
PVR after birth, there is Lt-to-Rt shunt and increased pulmonary blood flow.
Clinical Features:
It depend on the magnitude of Lt-to-Rt shunt, which determined by the size of PDA and
PVR (as in VSD).
1. Small PDA is asymptomatic.
2. Moderate-large PDA causing congestive heart failure (CHF) as the PVR decrease
over the first 6-8 wks of life
3. Findings on physical examination:
a. Wide pulse pressure.
b. Continuous machinery murmur at Lt infra-clavicular area, it may be associated
with thrill.
c. Hyperdynamic precordium in large PDA.
d. Splitted S2 occur with high pulmonary pressure.
Diagnosis:
1. CXR: shows full pulmonary artery shadow and increased pulmonary vascularity in
large PDA. But CXR might be normal in small PDA.
2. ECG: it varies from normal to evidence of LV hypertrophy or RV hypertrophy in
presence of pulmonary HT.
3. Echocardiography: for the size of PDA, magnitude of the Lt-to-Rt shunt and
pulmonary pressure.
Treatment:
1. Spontaneous closure of PDA after few wks of age is uncommon in full term infants.
2. Treatment of CHF with diuretics and digoxin.
3. Closure the PDA through the catheterization is recommended even in small PDA to
prevent subacute bacterial endocarditis.
COARCTATION OF THE AORTA:
occurs in approximately 10% of all CHD. It is almost always juxtaductal in position.
During development of the aortic arch, the area near the insertion of the ductus
arteriosus fails to develop correctly, resulting in a narrowing of the aortic lumen.
Clinical Manifestations
Infants with severe coarctation frequently dependent on a PDA to provide descending
aortic flow. Symptoms develop when the ductus close. Clinical manifestations include:
1. Symptoms including poor feeding, respiratory distress, and shock, may develop
before 2 weeks of age.
2. Classically the femoral pulses are weaker and delayed compared with the right
radial pulse.
3. The blood pressure in the lower extremities is lower than that in the upper
extremities.
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Older children are usually asymptomatic:
1. There may be a leg pain with exercise, headache, or epistaxis.
2. Decreased or absent lower extremity pulses and hypertension ( in upper
extremity).
3. The machinery murmur is typically best heard in the left interscapular area of the
back. If significant collaterals have developed, continuous murmurs may be heard
throughout the chest.
4. An abnormal aortic valve is present approximately 50% of cases, causing systolic
ejection click and systolic ejection murmur of aortic stenosis.
Diagnosis:
1. In infants, the ECG show evidence of right ventricular hypertrophy .
2. CXR show marked cardiomegaly and pulmonary edema.
3. Echocardiography shows the site of coarctation and associated lesions.
4. In older children, the ECG and chest x-ray usually show left ventricular
hypertrophy and a mildly enlarged heart. Rib notching may also be seen in older
children (>8 years of age) with large collaterals.
5. Echocardiography shows the site and degree of coarctation, presence of left
ventricular hypertrophy, and aortic valve morphology and function.
Treatment:
1. IV infusion of prostaglandin E1 (chemically opens the ductus arteriosus),
digoxin, diuretics, and other supportive care.
2. Balloon angioplasty, especially in critically ill infants, but surgical repair of the
coarctation is most commonly performed.
Tetralogy of Fallot (TOF):
It is the most common cyanotic CHD, represent about 10% of all CHD.
It consist of:
1. Large, non-restrictive VSD.
2. Rt ventricular out flow obstruction (pulmonary stenosis) which is most commonly
in the Rt ventricular infundibulum (supvalvular) or less commonly in the
pulmonary valve.
3. Rt sided aortic arch which overriding the ventricular septum (overriding of aorta).
4. Rt ventricular hypertrophy (RVH).
Pathophysiology:
Systemic venous return to right atrium and right ventricle is normal.
When the Rt ventricle contracts in the presence of marked pulmonary stenosis, blood is
shunting across the VSD into the Lt ventricle then into aorta (Rt-to-Lt shunt) causing
arterial desaturation and cyanosis. The severity of cyanosis depend on the degree of
pulmonary stenosis. In the severe pulmonary stenosis the pulmonary blood flow is
supplied by PDA.
Degree of Rt ventricular outflow obstruction determine the timing of onset of symptoms,
the severity of cyanosis and the degree of RVH.
In mild-
moderate Rt ventricular outflow obstruction, there’s balanced shunt across the
VSD and the patient is not v
isibly cyanosed (Acyanotic or “pink” TOF).
When the obstruction is severe, the cyanosis present at birth and worsen with closure of
ductus arteriosus.
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Clinical features:
1. Infants with mild pulmonary stenosis may be initially presents with heart failure due
to severe Lt-to-Rt shunt across large VSD.
Cyanosis is absent at birth, but it will appear latter in 1
st
year of life due to increased
pulmonary stenosis secondary to hypertrophy of right ventricular infundibulum.
2. Infants with severe pulmonary stenosis have cyanosis immediately in neonatal
period and pulmonary blood flow is depend on the ductus arteriosus. When the
ductus begin to close over the 1
st
few hours or days of life it will cause severe
cyanosis and circulatory collapse.
3. Older children with long-standing cyanosis have dusky blue skin, gray sclera with
engorged blood vessels and marked clubbing of fingers and toes.
4. Systolic ejection murmur due to pulmonary stenosis present in all patients which
best heard at the 2
nd
Left intercostal space and radiate to the back.
5.
Paroxysmal hypercyanotic attacks ( “cyanotic” or “blue” or “tet” spells):
It’s particular problem during the first 2 years of life occurs due to reduction of an
already compromised pulmonary blood flow precipitated by excessive crying,
vigorous exercise or systemic infection. If the spell is prolong, it will result in severe
systemic hypoxia and metabolic acidosis.
These spells are characterized by:
a. The onset is spontaneous and unpredictable.
b. Spells occurs most frequently in the morning on awaking or after vigorous crying.
c. Infants developed hyperpnea, increasing cyanosis, gasping breathing and might
end with syncope or death.
d. Temporary disappearance or reduction of ejection systolic murmur due to
decrease blood flow across the aortic valve.
e. The spells may last from a few minutes to a few hours. Short spells followed by
generalized weakness and sleep, while prolong severe spells may progress to
unconsciousness or convulsion or hemiparesis.
f. Toddler patient adapt squatting position during the spell in attempt to increase
systemic venous return and then increase pulmonary blood flow.
Note:
Infants who are only mildly cyanosed at rest are more liable to develop cyanotic
attacks because they lack the homeostatic mechanisms to tolerate rapid decrease of
arterial oxygen saturation such as polycythemia.
Diagnosis:
1. ECG: shows Rt axis deviation and RV hypertrophy.
2. CXR: shows boot-shaped heart (created by small main pulmonary artery and
upturned apex secondary to RVH) and oligemic lung fields.
3. Echocardiography: shows the anatomical features of TOF.
Treatment:
1. Treatment of hypercyanotic attacks:
Depending on the frequency and severity of hypercyanotic attacks,1 or more of the
following procedures should be done in sequence:
a. Knee-chest position of the infant which may prevent progression of an early spell.
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b. Oxygen administration (although increasing oxygen will not reverse cyanosis
because it’s due to intracardiac shunting).
c. S.C morphine in a dose not in excess of 0.2 mg/kg.
d. IV infusion of sodium bicarbonate if the spell is severe and not responding to
above measures.
e. Intubation and sedation are often sufficient to break the spell which is severe and
not responding to other treatments.
f. Drugs that increase systemic vascular resistance, such as intravenous
phenylephrine, can improve right ventricular outflow, decrease the right-to-left
shunt, and improve the symptoms.
g. IV propranolol (0.1 mg/kg given slowly to a maximum of 0.2 mg/kg).
2. Complete surgical repair with closure of VSD with removal of pulmonary stenosis
can be performed during infancy.
3. Palliative shunt surgery ( Blalock-Tausing shunt) in which a palliative shunt
created between subclavian artery (systemic circulation) and pulmonary artery. It
done for a complex TOF with complete repair later in life.
4. Prophylactic antibiotic to prevent subacute bacterial endocarditis.
Complications:
1. Cerebral thrombosis: Occurs as a complication of severe polycythemia and
dehydration. It most often in patient younger than 2 years.
2. Brain abscess: It less common than cerebral thrombosis and it usually occurs in
children older than 2 years.
3. Subacute bacterial endocarditis.
4. Heart failure:
Is unusual in TOF except in young infants with “pink” or “Acyanotic”
TOF and as the degree of pulmonary stenosis increase with age the symptoms of
heart failure resolved and the patient develop cyanosis often at 6-12 months of age.