Page 197 - Clinical Pearls in Cardiology

Radiology 185

X + Y
Cardiothoracic ratio =
Z
where,
X = Maximum distance from the center of spine to the
right border of heart.
Y = Maximum distance from the center of spine to the
left border of heart.
Z = Maximum internal thoracic diameter.
In people with normal sized heart, the cardiothoracic
ratio is usually less than 50%. In those with cardiomegaly,
the cardiothoracic ratio is more than 50%. A heart may
have higher (i.e more than 50%) cardiothoracic ratio
and still be a normal heart. This can occur if there is an
extracardiac cause of cardiac enlargement. Extracardiac
causes producing cardiomegaly on the chest X-ray
include the following:
1. Inability to take a deep breath because of obesity,
pregnancy or ascites.
2. Abnormalities of the chest wall that compress the
heart such as the pectus excavatum deformity,
straight back syndrome, etc.
3. Absent pericardium.
7. Which are the named radiological signs in congenital
heart disease?
Some of the important named radiological signs in
congenital heart disease are the following:

Radiological signs in congenital heart disease
Egg on side/egg on string Corrected TGA
Coeur en Sabot/Boot-shaped Tetralogy of Fallot
heart
Box-shaped heart Ebsteins anomaly
Contd...