Key result
CXR aortic knob diameter plus demographics detects aortic dilation with ~0.88 AUC.
Why the study?
While aortic knob width on chest radiography can reflect aortic dilation, standardized and widely recognized thresholds of clinical utility are lacking.
Does quantitative measurement of the aortic knob on routine posteroanterior chest radiography combined with age and sex accurately screen for and exclude aortic arch dilation (>40 mm) compared with chest CT angiography in emergency department patients?
Cohort (n=240)
No
Does quantitative measurement of the aortic knob on routine posteroanterior chest radiography combined with age and sex accurately screen for and exclude aortic arch dilation (>40 mm) compared with chest CT angiography in emergency department patients?
Simple quantitative measurement of horizontal aortic knob width on routine chest X-ray combined with age and sex provides a high negative predictive value (1.00) to safely rule out aortic arch dilation (>40 mm) and guide decisions for advanced CTA imaging.
May aid ruling out aortic dilation on chest X-ray; hypothesis-generating and requires prospective validation before adoption.
Background: Chest radiography (CXR) remains the most common first-line imaging for thoracic abnormalities. While aortic knob width can reflect aortic dilation, no standardized, widely recognized thresholds of clinical utility exist. Methods: This pilot retrospective study analyzed 240 emergency department patients (median age 67 years, 61% male) who underwent both PA CXR and chest computed tomography angiography (CTA) within 7 days. Three aortic knob dimensions (horizontal, oblique, vertical) were measured on CXR and compared with CTA measurements at two anatomical levels: proximal to the brachiocephalic trunk (P-BCT) and distal to the left subclavian artery (D-LSA). Results: The horizontal aortic knob width was most closely related to CTA measurements of P-BCT and D-LSA. A regression model incorporating horizontal knob diameter, age, and sex was characterized with an AUC of 0.884 (95% CI 0.825–0.944) for detecting aortic dilation (>40 mm). Using a conservative threshold with the upper 95% prediction bound exceeding 40 mm led to 100% sensitivity and 54% specificity, with a negative predictive value of 1.00. Conclusions: Simple quantitative CXR measurements of aortic knob width (horizontal), combined with age and sex, can provide additional confidence for excluding aortic arch dilation. Given further validation in diverse populations, if the high negative predictive value of this approach will be confirmed, it may represent a valuable screening tool to guide decisions for advanced imaging, especially due to low cost and wide availability.
No takes yet. Share an insight, caveat, or question.
Lis et al. (2025) conducted a cohort in Aortic arch dilation (>40 mm) (n=240). Quantitative posteroanterior chest radiography (CXR) horizontal aortic knob width measurement combined with age and sex vs. Chest computed tomography angiography (CTA) aortic arch dimensions at proximal to the brachiocephalic trunk (P-BCT) and distal to the left subclavian artery (D-LSA) was evaluated on Detection of aortic arch dilation (>40 mm) on chest CT angiography (AUC 0.884, 95% CI 0.825-0.944). Horizontal aortic knob diameter on chest X-ray combined with age and sex detected aortic dilation (>40 mm) with an AUC of 0.884 (95% CI 0.825–0.944) and 100% sensitivity.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: