AJR November 2018
University of Toronto
Toronto, Ontario, Canada
“Diagnostic Accuracy of Sex-Specific Chest CT Measurements Compared With Cardiac MRI Findings in the Assessment of Cardiac Chamber Enlargement”
Although cardiac MRI is considered the reference standard for evaluation of cardiac size and function, it is rarely performed as an initial investigation because of its high cost and limited availability. An article in the November 2018 issue of the American Journal of Roentgenology (AJR) shows that cardiac chamber enlargement can be identified with high specificity and reasonable sensitivity on axial chest CT images by use of sex-specific measurement thresholds.
Cardiac chamber enlargement is important to identify because it can be associated with adverse outcomes and may indicate a potentially treatable underlying pathologic condition. Researchers, led by Kate Hanneman, of the Toronto General Hospital and the University of Toronto, sought to establish sex-specific axial chest CT measurement thresholds to identify cardiac chamber enlargement with cardiac MRI as the reference standard.
The study assessed 217 patients who underwent contrast-enhanced chest CT and cardiac MRI within a seven-day period between August 2006 and August 2016. Measurements were taken on axial CT images to evaluate right atrial (RA), right ventricular (RV), left atrial (LA), and left ventricular (LV) chamber size. The presence of chamber enlargement for all four areas was established using cardiac MRI as a reference.
In men, the prevalence of chamber enlargement was 26 percent for RA, 11 percent for RV, 40 percent for LA and 24 percent for LV. In women, the prevalence for chamber enlargement was 16 percent for RA, 15 percent for RV, 27 percent for LA and 12 percent for LV.
The results showed that cardiac chamber enlargement can be identified with high specificity and reasonable sensitivity at non-gated chest CT by use of simple diameter measurements made on non-reformatted axial images.
In this Q&A, Hanneman discusses the authors’ ideas behind the study and the outlook for further research.
What is the background for this study? How did you and your co-authors come up with the idea?
Hanneman: Cardiac findings are often under-reported on chest CT. Given the widespread use of chest CT, it is important that radiologists have tools to help them identify cardiac chamber enlargement even when studies are performed for non-cardiac indications. Only a few prior studies have evaluated measurements made on non-gated chest CT to identify cardiac chamber enlargement. The purpose of our study was to establish sex-specific axial chest CT measurement thresholds to identify cardiac chamber enlargement using cardiac MRI as the reference standard. We evaluated sex-specific measurement thresholds given that cardiac chamber sizes are larger in males compared to females.
What should readers take away from your article?
Hanneman: The key finding from this study is that cardiac chamber enlargement can be identified with high specificity and reasonable sensitivity on routine non-gated chest CT using simple diameter measurements made on non-reformatted axial images. Sex-specific measurement thresholds were selected to ensure high specificity and then maximum sensitivity. Specificity was prioritized to minimize the number of false positives. Therefore, use of these measurement thresholds will help to rule in cardiac chamber enlargement with a high degree of confidence. Strengths of this study include a relatively large sample of subjects, sex-specific analysis, and comparison to cardiac MRI as the reference standard. The results of this study have the potential to identify patients with cardiac chamber enlargement who might benefit from further investigation and therapy.
What recommendations do you have for future research as a result of this article?
Hanneman: The diagnostic performance of CT measurement thresholds identified in this study could be confirmed in a multi-center study using a large external dataset.
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