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

Abstract

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. 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. 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). Observation of aortic knob on chest X-ray in hypertensive patients may provide important predictive information of subclinical atherosclerosis.