Abnormal mechanical properties of the aorta in Marfan's syndrome

Aortic dilatation, dissection and rupture are among the major causes of death in subjects with Marfan's syndrome. The aim of the study was to investigate the mechanical properties or compliance of the aorta in these subjects and compare them with a healthy age- and sex-matched reference population.

An ultrasound phase-locked echo-tracking system was used to determine diameter and pulsatile diameter change of the infrarenal aorta in nine subjects with Marfan's syndrome which were then compared with the values for 165 healthy individuals. Compliance, defined as the inverse of Ep (pressure strain elastic modulus) or stiffness (beta), was calculated from pulsatile diameter change and blood pressure obtained by the auscultatory method with a sphygmomanometer. For statistical analysis confidence intervals (95%) obtained from the healthy controls were used for comparison. Analysis of covariance (ANCOVA) was performed for the female patients. The sample size for males (n = 2) was too small for the latter analysis.

Compared with normal subjects and their confidence intervals, subjects with Marfan's syndrome had an increased Ep and stiffness (beta) and decreased strain (fractional diameter change) in the infrarenal aorta. Furthermore, ANCOVA in the female patients showed increased beta (p < 0.01) and Ep (p < 0.01) and a decreased strain (p < 0.001). Aortic diameters, MAP, as well as the pulse pressure, were similar in the two groups.

This investigation demonstrates alterations in the mechanical properties of the aorta in Marfan's syndrome in the form of increased stiffness of the aortic wall. This may be of importance in the pathogenesis of aortic dissection and rupture.