Background: Aortic knob width (AKW) is the measurement of the radiographic configuration composed of the foreshortened aortic arch and a part of the descending aorta. We investigated the relationship between the nondipper pattern and AKW.

Material and methods: All patients’ office blood pressure measurements and 24-hour ambulatory blood pressure readings were recorded. A blood pressure drop of less than 10% was defined as non-dipping. The patients were grouped into Group 1; dipper pattern (37 patients; 22F, and mean age 49.2 ± 11.7 yrs) and Group 2; non-dipper pattern (64 patients; 37F, and mean age 53.7 ± 13.1 yrs). On posteroanterior chest radiography, the widest point of the aortic knob was measured along the straight imaginary line from the lateral edge of the trachea to the left lateral wall of the aortic arch.

Results: AKW was significantly higher in Group 2 compared to group 1 (36.7 ± 5.7 vs. 30.7 ± 4.5 mm, p < 0.001). The mean daytime and night-time systolic blood pressures, the mean night-time diastolic blood pressure levels, 24-hour mean blood pressure and mean pulse pressures were higher; percentage of nocturnal drops was significantly lower in Group 2 compared to Group 1. AKW was determined to be the parameter that was mostly related to the non-dipper pattern. A ROC analysis revealed that the area under the curve values for AKW values of non-dippers were 0.796 (95% CI: 0.707–0.884, p < 0.001).

Conclusion: AKW is significantly higher in non-dipper individuals compared to dippers. AKW values above
32.6 mm on the chest radiograph may be associated with non-dipper pattern especially in hypertensive individuals.