The effect of pre-procedure sublingual nitroglycerin on radial artery diameter and Allen's test outcome - Relevance to transradial catheterization.

Background: The radial artery is increasingly used for cardiac procedures, but is a relatively small vessel that is prone to spasm when instrumented. Intra-arterial nitroglycerine has been shown to reduce radial spasm but first requires arterial access. We investigated the effect of pre-procedure sublingual nitroglycerin (NTG) on the diameter of the radial artery in a large cohort of patients.

Methods: 305 subjects underwent ultrasound measurement of their radial and ulnar arteries in both arms before and after the administration of 800μg of sublingual NTG. The Allen's test was also performed in the subjects prior to and after NTG.

Results: Radial artery diameter in this Caucasian study group is larger than that reported for other populations. The administration of sublingual NTG significantly increased the size of the right radial artery from 2.88±0.36mm to 3.36±0.40mm in men and from 2.23±0.37 up to 2.74±0.36mm in women. There were also significant increases in left radial, right and left ulnar artery diameters in males and females with NTG. There was no significant effect of NTG on blood pressure. In all patients with an unfavourable Allen's test, retesting following sublingual NTG resulted in transition to a favourable Allen's.

Conclusion: Caucasian populations have larger calibre radial arteries compared to other geographic areas. Sublingual NTG is effective at dilating the radial artery in both men and women. This may make radial artery puncture and cannulation less challenging and should be considered in all patients in the absence of contraindications. The results of Allen's testing are dynamic and its usefulness for screening prior to transradial access is undetermined.