Page 161 - Clinical Pearls in Cardiology

Congenital Heart Disease 149

predominant left-to-right shunting of blood, and
these people usually present in adulthood as
acyanotic or ‘pink’ Fallot.
4. Right ventricular hypertrophy producing left
parasternal heave and boot-shaped heart. This
produces the Coeur en Sabot appearance on the
chest X-ray.
15. What is ‘Tet spell’ in tetralogy of Fallot?
The “Tet spell” (also called ‘hypoxic spell’, ‘cyanotic
spell’, or ‘hypercyanotic spell’) is an episodic central
cyanosis due to an increase in right ventricular outflow
tract resistance in a patient with a congenital heart
disease, such as tetralogy of Fallot. Hypercyanotic spell
is characterized by paroxysm of hyperpnea, irritability,
prolonged cry, increased cyanosis and decreased
intensity of heart murmur. If not treated in time, it may
lead to seizures, neurological deficit and death. A spell
is most likely to occur in a child less than two years of
age, upon waking up in the morning or following a crying
episode.
16. How does squatting improve cyanosis in a case of
Fallot’s tetralogy?
In a person with tetralogy of Fallot, normally most of the
deoxygenated blood that enters into the right ventricle
is shunted across the large septal defect into the over-
riding aorta, without going through the lungs as shown
in the Figure 4.
When a person assumes squatting or knee-to-chest
position, it increases the systemic vascular resistance and
aortic root pressure. This decreases the amount of blood
that is shunted directly into the aorta across the large
ventricular septal defect from the right ventricle. Hence