CARDIO-THORACIC RATIO

Cardio-Thoracic ratio: Widest diameter of the heart compared to the widest internal diameter of the rib-cage.

Figure 1 Cardio-thoracic ratio

Sometime the Cardio-Thoracic ratio (CTR) is more than 50 % but the heart is Normal, it can be possible due to extra-cardiac causes of cardiac enlargement like:

Ø  Portable AP films

Ø  Obesity

Ø  Pregnant

Ø  Ascities

Ø  Straight back syndrome

Ø  Pectus excavatum

 

 

 

 

 

 

Figure 2 CTR >50 %

On the picture 2 we can see a heart that is larger than 50 % of the CTR, but it is still normal, because there is an extra-cardiac cause for the apparent cardiomegalic, on the lateral films we see the red arrow point to the inward displacement of the lower sternum in a pectus excavatum deformity.

Also we can found the CTR less than 50 % but the heart is abnormal.

Causes:

Ø  Obstruction to Outflow of the ventricles

Ventricle hypertrophy

Ø  “Must look at cardiac contours”

 

 

 

 

 

 

 

Figure 3 CTR < 50 %

This is an example of heart which is less than 50 % of the CTR in which the heart is still abnormal, yellow arrow show a recognizable abnormal contour to the heart.

Retrieved from: http://www.learningradiology.com/lectures/cardiaclectures/abcsflashnew.swf