Noninvasive ultrasound measurements of aortic intima-media thickness: implications for in vivo study of aortic wall stress.

OBJECT: The abdominal aorta (AA) has a predilection for aneurysm formation. An etiologic factor may be underlying aortic wall stress. The purpose of this study was to examine whether the intima-media thickness (IMT) of the AA, as a surrogate to arterial wall thickness, can be measured noninvasively with satisfactory results to calculate circumferential wall stress, and to evaluate regional and gender differences in wall stress.

METHODS: Sixty-five middle-aged healthy subjects were examined with B-mode ultrasound to determine the diameter and IMT in the infrarenal AA, common carotid artery (CCA), common femoral artery (CFA), and popliteal artery (PA). Blood pressure was measured noninvasively in the brachial artery. Wall stress was calculated according to the law of LaPlace.

RESULTS: Intraobserver variability for the IMT in the AA showed a coefficient of variation of 11%. IMT was thickest in the AA compared with the CCA, CFA, and PA (P <.001). There was a gender difference in IMT in the CFA (P <.05) and PA (P <.01) but not in the AA. Greater wall stress was found in the AA than in the CCA (P <.001) and PA (P <.001), with men having greater wall stress in all studied arterial regions.

CONCLUSIONS: Aortic IMT can be satisfactorily studied in vivo with noninvasive B-mode ultrasound. There are gender differences in IMT and wall stress, and the largest wall stress is found in the AA in men, which might be important in aneurysm development.