Revision 15 for 'Cardiothoracic ratio'All Revisions
Some report CTR as a percentage, however this is strictly incorrect, as it is a ratio.
The CTR is measured on a PA chest x-ray, and is the ratio of maximal horizontal cardiac diameter to maximal horizontal thoracic diameter (inner edge of ribs / edge of pleura). A normal measurement should be ≤0.5.
It should be noted that this measurement is a coarse marker of disease 4. If the patient is symptomatic then echocardiography is required but the yield of echocardiography is low if performed just for an increased CTR 3.
In this situations, cardiothoracic ratio is more than 0.5 on a PA radiograph, but heart is normal:
- a prominent epicardial fat pad
- due to expiration
- Pectus excavatum
- straight back syndrome