Axial chest CT IDs chamber enlargement with high specificity, reasonable sensitivity

Cardiac chamber enlargement can be identified with high specificity and reasonable sensitivity on axial chest CT images by use of gender-specific measurement thresholds, according to new research published in the American Journal of Roentgenology. 

While cardiac MRI is considered the reference standard for the evaluation of cardiac size and function, it is rarely used as the initial imaging modality due to expense and limited availability. Contrast-enhanced chest CT is a more viable option, though few studies have evaluated measurements made during non-ECG-gated chest CT in comparison with echocardiography or cardiac MRI to identify cardiac chamber enlargement.  

Researchers, led by Kate Hanneman, MD, of the Toronto General Hospital and the University of Toronto, in Ontario, Canada, noted no studies have established gender-specific chest CT measurement thresholds for detection of cardiac chamber enlargement.

A total of 217 patients who underwent contrast-enhanced chest CT and cardiac MRI within a seven-day period between August 2006 and August 2016 were assessed. 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. The researchers identified the optimal CT measurement thresholds for men and women, that ensured specificity of at least 90 percent and maximized sensitivity.

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 researchers found the following CT measurement thresholds as optimal:

  • For RAE (enlargement), RA transverse diameter should be greater than or equal to 67 mm for men and greater than or equal to 64 mm for women.
  • For RVE, RV transverse diameter should be greater than or equal to 60 mm for men and greater than or equal to 57 mm for women.
  • For LAE, LA anteroposterior diameter should be greater than or equal to 50 mm for men and greater than or equal to 45 mm for women.
  • For LVE, LV transverse diameter should be greater than or equal to 58 mm for men and greater than or equal to 53 mm for women.
  • In all cases, optimal measurement thresholds identified were larger for men than for women.

“Measurement thresholds identified in this study have reasonable sensitivity to help rule out underlying cardiac disease when a measurement is below the recommended threshold,” the researchers noted. “Given that chamber enlargement is not a life-threatening condition, these modest sensitivities are not unreasonable.”

Hanneman and colleagues noted a key limitation of the study is measurements were obtained with newer scanners; therefore, their thresholds may not apply to older scanners.

“The results of this study show 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,” the researchers concluded.