Background Evaluation of regional aortic elastic properties in humans has been hampered by the need for invasive techniques to access instantaneous aortic pressure, wall thickness, and cross-sectional area or diameter. In this study, a new noninvasive method is presented for quantification of regional aortic elastic properties.Methods and Results Twenty-five patients were studied during transesophageal echocardiographic procedures. Measurements of instantaneous aortic cross-sectional area were obtained with an automated border detection algorithm applied to short-axis transesophageal two-dimensional echocardiographic images of the proximal descending thoracic aorta. Instantaneous aortic wall thickness was derived from combined two-dimensional targeted M-mode end-diastolic wall thickness and instantaneous aortic area measurements. Instantaneous aortic pressures were estimated from calibrated subclavian pulse tracings recorded simultaneously. Data were digitized to generate aortic area-pressure loops. Regional aortic mechanical properties were quantified in terms of compliance per unit length (C is the slope of the area-pressure regression), aortic midwall radius (R sub m), and incremental elastic modulus of the aortic wall (Einc). To assess the independent effect of age, Rmand Eincvalues were compared at a common level of aortic midwall stress (0.666 x 106dynes/cm2). Mean values (+-SD) for C, Rm, and Eincwere 0.01+-0.004 cm2/mm Hg, 1.14+-0.17 cm, and 7.059+-4.091 x 106dynes/cm2, respectively. An inverse linear correlation was found between aortic compliance per unit length and age (r=-.68, P<.0007). Incremental elastic modulus was related to age (r=+.80, P<.00003) in a nonlinear fashion such that it increased sharply after the age of 60 years. Finally, midwall radius was less tightly correlated with age (r=+.45, P<.05). Values for C, Rm, and Eincas well as the age dependency of these properties are similar to those reported previously when invasive techniques were used.Conclusions This methodology constitutes a new tool to improve the clinical evaluation of regional aortic elastic properties in multiple disease states. (Circulation. 1994;90:1875-1882.)