cardiothoracic ratio
Measurement on chest X-ray comparing cardiac width to thoracic width, used to assess heart size and detect cardiomegaly.
Full Definition
A radiographic measurement calculated by dividing the maximal cardiac width by the maximal thoracic width on a posteroanterior chest X-ray. Normal cardiothoracic ratio is less than 0.5 (or 50%) in adults. Values greater than 0.5 suggest cardiomegaly, which may indicate heart failure, valvular disease, or other cardiac pathology. In surgical critical care, the cardiothoracic ratio helps assess fluid status, cardiac function, and response to resuscitation. The measurement is less reliable on portable or anteroposterior films due to magnification effects and patient positioning.
Usage
Usage note: Often abbreviated as CTR; hyphenated when used as compound modifier.
In Context
- "The chest X-ray showed a cardiothoracic ratio of 0.6, suggesting cardiomegaly." — Radiology interpretation
- "Serial chest films demonstrated improving cardiothoracic ratio with diuresis." — Critical care monitoring