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Title: The relationship between aortic aneurysm WA4 distensibility and aneurysm growth and rupture
Author: Wilson, K. A.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2002
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Aims: The primary aim was to determine the relationships between AAA wall distensibility, diameter, expansion and risk of rupture. Secondary aims were to evaluate the variability of the technique and to assess the error caused by use of brachial, as opposed to central, blood pressure. Methods: Distensibility [pressure-strain elastic modulus (Ep) and stiffness (β)] was measured using a real time B-mode ultrasound scanner with echo-tracking software (Diamove). Brachial pressure was measured using automated sphygmomanometry (Omron, Japan). Central aortic pressure was derived using pulse wave analysis (Sphygmocor), Follow-up was 6-monthly for a median (IQR) period of 19.7 (9.2-29.9) months. Results: 210 patients (163 males and 47 females) were recruited. Median (IQR) age was 72 (68-77) years, AAA diameter 48 (41-54) mm, BP 140/80 (128-160/72-90) mmHg, Ep 2.91 (1.99-4.37) 105Nm-2, and β 19.4 (14.4-29.4). Intra- and inter-observer CVME for directly measured variables were low (10%) while CVME for the derived variables were higher (35%). The CVME is a parametric test; however, when these skewed data were logged to normality intra-observer CVME for β was 10%. Bland-Altman plots showed that Ep and β calculated using brachial, as opposed to derived central pressure, were systematically over-estimated by 11% (p=0.001) and 5% (p=0.040) respectively. At baseline, AAA in the rupture group tended towards being more distensible than the intact AAA but this did not attain statistical significance. At last follow-up, the rate and direction of change in distensibility were not related to diameter or expansion. Cox proportional hazard model showed that, after adjusting for age and sex, female gender, larger AAA diameter, higher diastolic pressure and a larger proportional increase in distensibility were related to a shorter time to rupture (all p 0.01).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available