The relationship between abdominal aortic aneurysm wall compliance, maximum diameter and growth rate

Aim: Aortic compliance as measured by the pressure-strain elastic modulus ( Ep) and stiffness (beta) may allow a more precise estimate of rupture risk The aim of this study was to determine the relationships between compliance , maximal aneurysm diameter and growth rate. Methods: Sixty abdominal aorti c aneurysm patients of median age 73 years, were studied. Growth rate was d erived from repeat ultrasound scans obtained over a median period of 21 mon ths (range 6-48), At the end of follow-up, patients underwent measurement o f maximum aortic diameter, Ep and beta using the Diamove echo-tracking syst em. Results: Growth rate correlated positively (r = 0.6, P < 0.01) with max imum diameter on entry to the study There was a positive correlation betwee n mean arterial pressure and Ep (r = 0.3, P = 0.03), but not between mean a rterial pressure and beta (r = 0.8, P = 0.61). A positive correlation was f ound between final maximum diameter and Ep (r = 0.22, P = 0.04) but not bet a (r = 0.16, P = 0.11). There was no significant relationship between growt h rate and Ep or beta. Conclusion: Large aneurysms tended to be less compli ant. Within a population of abdominal aortic aneurysm of similar maximum di ameter there was a 10-fold variation in Ep and beta. Compliance and growth rate were not related. If aortic compliance is related to risk of rupture t hen this predictive information is likely to be largely independent of that currently obtained from size and growth rate. (C) 1999 The International S ociety for Cardiovascular Surgery. Published by Elsevier Science Ltd. All r ights reserved.