Background: Palpation-guided access of the radial artery (RA) has transradial access (TRA) failure rates averaging 6%-7%. This study aimed to measure RA and ulnar artery (UA) diameters by ultrasound in a typical American population, in hopes of elucidating data that may improve TRA success rates.
Methods: Intraprocedural ultrasound measurements of the RA and UA in 565 consecutive patients undergoing TRA were retrospectively analyzed.
Results: The RA is usually larger than the UA, with diameters of 3.0 mm and 2.7 mm, respectively. The UA was larger than the RA in 23% of the population studied, being larger than the RA by ≥20% in 6.5%. Men have larger RAs and UAs than women, with RA/UA diameters of 3.2/2.7 mm and 2.8/2.4 mm, respectively. Body mass index did not correlate with RA diameter. An RA to sheath ratio of <1.0 would have occurred in 6% of men and 16% of women with the use of a 6-Fr slender sheath. The distal RA was 0.5 mm (16%) smaller in diameter than the RA.
Conclusions: The RA is usually larger than the UA and will be the artery of choice for access in most patients. The UA was larger than the RA by ≥20% in 6.5% of patients studied, possibly making it the wrist artery of choice for access in many of these patients. No clinical variables predict RA or UA diameters. Ultrasound may improve TRA success rates by allowing accurate sizing of the RA/UA, thereby preventing inadvertent sheath oversizing causing radial artery spasm and TRA failure.
Keywords: radial artery; ulnar artery; ultrasound guidance; vascular access; transradial access.