RADAR: Transradial access safe, feasible regardless of Allen's test results

Thumb capillary lactate after transradial procedures was similar among patients with normal, intermediate or abnormal Allen’s test results, providing what researchers called a proof of concept for a paradigm shift in CV intervention.

In the RADAR study, researchers examined whether transradial coronary catheterization across the whole spectrum of Allen’s test results was safe and feasible to address the current uncertainty about the predictive capacity of the Allen’s test for transradial access.

The accrual period ran from October 2007 to June 2009. From the 942 screened patients, 203 were recruited for the study. Eighty-three patients presented a normal Allen’s test result, whereas 60 were intermediate and 60 were abnormal.

Clinicians assessed the thumb capillary lactate of the patient population, the study’s primary endpoint. They also evaluated thumb plethysmography and ulnar frame count, the aim of which was to investigate patency of the ulnopalmar arches. Other tests included a handgrip strength test to examine isometric strength of the hand and forearm muscles, and discomfort rating.

No difference was reported among the three arms in terms of lactate after the procedure. The result in the normal group was 1.85 ± 0.93 mmol/L compared with 1.85 ± 0.66 mmol/L for intermediate and 1.97 ± 0.71 mmol/L for abnormal (P=0.59). This result held through all time points of the study.

Patients with non-normal Allen’s test results demonstrated improvement in ulnopalmar collaterization, according to plethysmography readings. However, these readings indicated decreases in ulnar frame count in this group. The investigators suggested that this may be a sign of enhanced ulnar flow in abnormal patients.

No differences were reported across the three test groups with regard to handgrip test results or discomfort rating. Additionally, there was no report of hand ischemic complications.

“Our study provides proof of concept for a paradigm shift in cardiovascular intervention, suggesting safety and feasibility of [transradial access] across the whole spectrum of [Allen’s test] results,” the researchers concluded. “Given the multiple implications of our findings, a broader clinical validation is needed.”

Olivier F. Bertrand

In an accompanying editorial, Olivier F. Bertrand, MD, PhD, Patrick C. Carey, JD, and Ian Gilchrist, MD, noted that just 22% of the original 942 screened patients stayed with the study to completion.

“In a typical [patient] population referred for elective catheterization, 60% of patients had a mean time to re-color the skin ≥6 seconds after releasing the ulnar artery compression and maintaining occlusion of the radial artery,” they wrote. “Conversely, the D pattern after plethysmography-oxymetry thought to indicate poor collateralization between vascular palmar arches was found in 40% of the cases but only in patients with abnormal Allen’s test. This indicates that in patients referred for coronary angiography, compression of the radial artery while having the ulnar artery patent will lead to very variable results in terms of timing to the subjective assessment of skin coloration or the more objective reading of oxymetry-plethysmography curves.”

Bertrand, Carey and Gilchrist highlighted that the study clearly demonstrates the primary outcome measure up to 1 year, adding that the results are similar to previous results from a research group in Canada.

“Based on the RADAR results, we believe that the denial of radial access for diagnostic angiography or interventions based solely on an abnormal [Allen’s test] or oximetry-plethysmography curve is not warranted since these tests are not scientifically predictive of pathologic rises in lactate levels, weakness in the hand or persisting discomfort during or after transradial catheterization,” they wrote. “Time has come to remove the Allen’s test from pre-procedural triage for transradial catheterization. We need to refocus our attention on the use of the oxymetry-plethysmography and other techniques to guide ‘patent-hemostasis’ once the transradial procedure is completed to minimize [right anterior oblique].”

For more information:

Bertrand OF. J Am Coll Cardiol. 2014;[published online ahead of print Feb. 26].

Valgimigli M. J Am Coll Cardiol. 2014:[published online ahead of print Feb. 26].

Disclosure: One researcher reports financial disclosures with Abbott Vascular, CID, Cordis, Daiichi Sankyo, Eli Lilly, Iroko, Medtronic, Merck, St. Jude Medical, Terumo and The Medicines Company. Bertrand, Carey and Gilchrist report no relevant financial disclosures.