Comparison of brachial artery pressure and derived central pressure in themeasurement of abdominal aortic aneurysm distensibility

Objective. AAA distensibility (Ep, beta) may predict growth and risk of rup ture, However, distensibility measurements based on brachial rather than ce ntral pressure may be inaccurate. Our aim was to compare AAA distensibility using non-invasive brachial and derived central aortic pressure. Design: brachial and central pressures were measured prospectively by autom ated sphygmomanometry (Omron) and pulse wave analysis (SphygmoCor) respecti vely. AAA distensibility was calculated using brachial (Ep(b), beta (b)) an d central (Ep(c), beta (c)) pressures by ultrasonic echo-tracking (Diamove) , Twenty-eight patients (18 males) were selected on a first come basis from a larger study of AAA patients. There were no exclusion criteria, so 54% h ad cardiac dysfunction (MI, angina) and 14% were hypertensive (BP > 140/90 mmHg). Results: median (IQR) age was 74 (70-77) years, median AAA (IQR) diameter w as 44 (40-51) min. Central and brachial systolic pressures were significant ly different, [140 (121-153) vs 144 (130-164) mmHg respectively, p less tha n or equal to0.01]. Central and brachial diastolic pressures were not signi ficantly different [76 (72-86) vs 76 (71-86) mmHg respectively, p=0.5]. Ey( c) (3.0, [2.2-4.9]) and beta (c) (22.2 [15.5-33.2]) were significantly lowe r than Ep(b) (3.6, [2.4-5.1] 10(5)Nm(-2)) and beta (b) (24.7 [17.1-33.0] a. u., all p <0.001. Brachial and central derived distensibility remained sign ificantly different after adjusting for age and diameter (p<0.001). Conclusion: the use of brachial pressure leads to a small, systematic overe stimate of Ep (18%) and <beta> (11%) independent of age and AAA diameter. T his systematic error will not bias follow-up of changes in distensibility.