Abdominal Aortic Aneurysm Wall Mechanics and their Relation to Risk of Rupture

Abstract

Purpose to see whether aneurysmal aortic wall mechanics can be used as a predictor of abdominal aortic aneurysm (AAA) rupture. Method among 285 individuals, followed conservatively for AAA and monitored for aneurysm growth and wall mechanics on at least one occasion at our institution between January 1991 and January 1998, eleven subsequently ruptured. Wall mechanics were estimated as stiffness (β). This was calculated from diameter and pulsatile diameter change, determined non-invasively by an ultrasonic echo-tracking system and blood pressure obtained by the auscultatory method. The results were compared with those of 121 individuals electively operated on for AAA. Results no difference in aortic stiffness was found between those that subsequently ruptured (β=35, median) compared to those non-ruptured (β=38, median) AAAs (p=0.855). There was no difference in diameter in ruptured (58.8 mm) compared with non-ruptured (54.1 mm) AAAs (p=0.129). All ruptured AAAs showed an expansion of diameter over time. Conclusion this study shows no difference in aneurysmal aortic wall mechanics in those AAAs that subsequently ruptured compared with electively operated AAAs. The results indicate that it is not possible to use aneurysmal aortic wall stiffness as a predictor of rupture.