Prospective radial artery study following induction of reactive hyperemia looking at degree of diameter growth in healthy subjects.

Objectives: This "proof of concept" study sought to determine the magnitude of radial artery diameter change in 20 healthy subjects by induction of flow mediation dilatation (FMD) via reactive hyperemia.

Background: Transradial access in the cardiac catheterization laboratory is becoming more commonplace due to lower bleeding complications and increase in patient comfort. However, access to the radial artery can be challenging due to small vessel size. We sought to examine whether FMD can be used to increase radial artery diameter, potentially allowing improved transradial access.

Methods: We obtained baseline radial artery diameter via a high frequency ultrasound probe on 20 healthy subjects. A standard reactive hyperemia protocol was employed in the right arm, followed by successive measurements of the subject's radial artery at pre-specified intervals. Radial artery diameter measurements were performed offline by the sonographer and also a blinded reader to which agreement was sought.

Results: We found a mean increase in radial artery size of 0.48 ± 0.13 mm at peak reactive hyperemic states. This correlated to a mean increase in overall radial artery diameter of 21.7 ± 6.7%. The median time to peak dilation was 30 seconds (95% CI; 15-45 seconds), and the median duration of maximal dilation was 60 seconds (95% CI; 45-75 seconds).

Conclusions: Among healthy subjects, we demonstrated a mean maximal increase in radial artery diameter of 21.7 ± 6.7% via FMD. This finding supports the notion that radial artery diameter can be increased noninvasively via a reactive hyperemia protocol.