Brachial Artery Dimensions, Reactivity And Distensibility With Advancing Age

Abstract

PURPOSE To examine brachial artery diameter, reactivity, distensibility, and pulse pressure from the second through the tenth decade of life. METHODS A total of 86 men (Age: 56±24, Range: 81, Min: 18, Max: 99 years) underwent highresolution ultrasonography (Toshiba Power vision SSA-380A, 7.5-MHz linear array transducer) of the brachial artery before and after 5 minutes of forearm occlusion. Prior to imaging subjects were instructed to fast and refrain from exercise for 12hr and alcohol for 48hr. Following 10min of supine rest, baseline images were obtained in longitudinal view. In addition, blood pressure and heart rates were obtained through out the procedure. Subsequently, subjects were categorized according to decade of life. Diastolic and systolic images were analyzed using semi-automated edge-detecting analysis software (Medical Imaging Applications, LLC). Brachial artery flow-mediated dilation (BAFMD) was defined as the percent change (%) in vessel diameter from rest to peak dilation following 5 min of forearm occlusion. Brachial arterial distensibility was characterized as a change in vessel cross-sectional area between diastole and systole over a change in pulse pressure (Kool M et al. 1994). Pulse pressure (PP) was calculated as systolic minus diastolic blood pressure RESULTS:For each decade of life resting brachial artery diameter (RBA) and PP increased. In contrast, BAFMD and distensibility decreased. These changes were best described by the following linear regressions: RBA=2.29+0.18* decade of life, r2=0.26 (Increase of 0.16 mm/decade); PP=19.71+4.79*decade of life, r2=0.35 (Increase of 4.26 mmHg/decade); BAFMD=11.77- 0.91* decade of life, r2=0.26 (Decrease of 0.80 %/decade); Distensibility =0.0015+ 0.00008* decade of life, r2=0.07, p=0.001 (Decrease of 0.7*10 -4μ/kPa/decade). Finally, BAFMD was significantly related to the RBA (r=−0.703, p=0.01), distensibility (r=0.426, p=0.01), and PP (r=−0.454, p=0.01. The influence of PP on BAFMD across the decades is described by the following equation: BAFMD=10.44–0.09*PP, r2=0.16. CONCLUSIONS These data confirm that advancing age is associated with increased resting diameter, reduced reactivity and distensibility of the brachial artery. A widening of PP may be a contributing factor or consequence of these vascular changes. Supported by the National Institute on Aging [P01 (AG022064091A1)] and the Louisiana Board of Regents through the Millennium Trust Health Excellence Fund [HEF (2001–06)02]