Relationship of aortic knob width with cardio-ankle vascular stiffness index and its value in diagnosis of subclinical atherosclerosis in hypertensive patients: a study on diagnostic accuracy

Objective: The aim of our study was to determine the usefulness of the aortic knob width (AKW) in the assessment of subclinical atherosclerosis in hypertensive patients. Methods: In this study on diagnostic accuracy, 374 consecutive hypertensive patients with at least one cardiovascular risk factor were enrolled. AKW was measured on chest X-ray. Cardio-ankle vascular index (CAVI) was measured by VaSera-1000 CAVI instrument. The diagnostic value of AKW was assessed using ROC analysis. Results: There was a significant correlation between aortic knob width and CAVI (r=0.45, p 0.001), age (0.39, p 0.001), systolic (r=0.17, p 0.001), diastolic (r=0.23, p 0.001) and mean (r=0.2, p 0.001) blood pressures. In linear regression analysis CAVI (β=0.3, 95% CI 0.33-0.98, p 0.001), age (β=0.3, 95% CI 0.09 - 0.21, p 0.001) and diastolic blood pressure β=0.2, 95% CI 0.08-1.9, p 0.001) were independently associated with AKW. It was significantly higher in patients with subclinical atherosclerosis (CAVI ≥9) than borderline (8 ≤CAVI 9) (41.4±5.5 versus 36.7±5.3 mm, p 0.001) and healthy (CAVI 8) subjects (41.4±5.5 versus 35.5±4.3 mm, p 0.001). Analysis using the ROC curve has demonstrated that aortic knob of 41 mm constitutes the cut-off value for the presence of subclinical atherosclerosis with 71% sensitivity and 77% specificity (AUC-0.67, 95% CI 0.51-0.82). Conclusion: Observation of aortic knob on chest X-ray in hypertensive patients may provide important predictive information of subclinical atherosclerosis.