Related Experiment Video
Updated: Oct 14, 2025
Quantification of Mouse Heart Left Ventricular Function, Myocardial Strain, and Hemodynamic Forces by Cardiovascular Magnetic Resonance Imaging
Published on: May 24, 2021
Limitations of cardiothoracic ratio derived from chest radiographs to predict real heart size: comparison with
Paulius Simkus1, Manuel Gutierrez Gimeno1, Audra Banisauskaite1,2
1Radiology Department, Liverpool Heart and Chest Hospital, Thomas Drive, Liverpool, L14 3PE, UK.
Insights
The cardiothoracic ratio (CTR) on chest X-rays poorly indicates true heart size. Cardiac MRI is more accurate for assessing cardiac enlargement, suggesting clinical decisions based on intermediate CTR values should be avoided.
Area of Science:
- Cardiology
- Radiology
- Medical Imaging
Background:
- Cardiothoracic ratio (CTR) is a widely used but potentially inaccurate method for estimating cardiac size.
- Newer imaging techniques like cardiac MRI offer more precise volumetric and functional assessments.
- This study investigates the limitations of CTR compared to cardiac MRI.
Purpose of the Study:
- To compare the accuracy of cardiothoracic ratio (CTR) with cardiac magnetic resonance imaging (MRI) in assessing cardiac size.
- To evaluate the correlation between CTR and volumetric/functional parameters from cardiac MRI.
- To determine the discriminatory power of CTR for identifying cardiac enlargement.
Main Methods:
- A review of 309 patients with both chest radiographs and cardiac MRI within one month.
- Correlation analysis between CTR and bi-ventricular end-diastolic volume (EDV), ejection fraction (EF), indexed total heart volume, and bi-atrial areas.
- Receiver Operating Characteristic (ROC) curve analysis to assess CTR accuracy.
Main Results:
- A weak but statistically significant correlation was found between CTR and all cardiac MRI variables.
- Substantial overlap in cardiac MRI parameters between normal and enlarged CTR groups was observed.
- CTR showed only mild to moderate discriminatory power (AUC 0.6-0.7) for cardiac enlargement.
Conclusions:
- CTR demonstrates weak correlation and discriminatory power compared to gold-standard cardiac MRI.
- Clinical decisions based on intermediate CTR values (45-55%) are not recommended.
- High CTR (>55%) likely indicates true chamber enlargement, while low CTR (<45%) suggests normal heart size.
Background:
Cardiothoracic ratio (CTR) in chest radiographs is still widely used to estimate cardiac size despite the advent of newer imaging techniques. We hypothesise that a universal CTR cut-off value of 50% is a poor indicator of cardiac enlargement. Our aim was to compare CTR with volumetric and functional parameters derived from cardiac magnetic resonance imaging (MRI).
Methods:
309 patients with a chest radiograph and cardiac MRI acquired within a month were reviewed to assess how CTR correlates with multiple cardiac MRI variables: bi-ventricular EDV (absolute and indexed to body surface area), EF, indexed total heart volume and bi-atrial areas. In addition, we have also determined CTR accuracy by creating multiple ROC curves with the described variables.
Results:
All cardiac MRI variables correlate weakly but statistically significantly with CTR. This weak correlation is explained by a substantial overlap of cardiac MRI parameters in patients with normal and increased CTR. For all variables, CTR was only mildly to moderately better than a chance to discriminate cardiac enlargement (AUC 0.6-0.7). Large CTR values (> 55%) are specific but not sensitive, while low CTR values (< 45%) are sensitive but not specific. Values in between are not sensitive nor specific.
Conclusions:
CTR correlates weakly with true chamber size assessed by gold standard cardiac MRI and has a weak discriminatory power. Thus, clinical decisions based on intermediate CTRs (45-55%) should be avoided. Large CTRs (> 55%) are likely indicative of true heart chamber enlargement. Low CTRs (< 45%) are likely indicative of normal heart size.
More Related Videos
Related Concept Videos
01:20Imaging Studies for Cardiovascular System III: X-Ray
Definition and Purpose
An X-ray, or radiograph, is a non-invasive method that uses ionizing radiation to take images of internal structures. It is mainly used in cardiac imaging to examine the heart, lungs, and major blood vessels, aiming to identify abnormalities in the heart's size, shape, and position, such as heart failure, congenital defects, and vascular...
01:21Imaging Studies for Cardiovascular System IV: CMRI
01:28Imaging Studies for Cardiovascular System V: CT
01:24Magnetic Resonance Imaging
01:29Cardiomyopathy IV: Restrictive Cardiomyopathy
01:23Mitral Stenosis II: Clinical features and Diagnostic Tests