Allen`s Testing Prior to Transradial Cardiac Catheterization: State of the Arch

“Percutaneous entry into the distal radial artery and selective coronarography using a French 5 sheath and preshaped catheters were attempted in 100 patients with a normal Allen test… With experience, this approach may become as effective and possibly safer than the transbrachial entry.” – Campeau L, 1989¹

Percutaneous radial arteriotomy for hemodynamic monitoring and vascular access was introduced over six decades ago.² The seminal paper on the transradial approach for coronary angiography by Campeau in 1989, several decades after the introduction of radial artery use for blood pressure monitoring, paved the way for a paradigm shift in cardiac catheterization access.¹ Since then, utilization of transradial procedures has increased substantially, propelled by refinements in technology and techniques, and a growing emphasis on bleeding reduction strategies. With more widespread utilization of the radial artery for vascular procedures, there has been increasing scrutiny of the true safety of the radial approach. Although there is a dual blood supply to the hand and rich collateralization via interosseous channels, there has been a long-held belief that all patients should be screened for patency of the palmar arch prior to radial access.² Radial artery occlusion (RAO), albeit uncommon, is regarded to be the most frequent complication of transradial access (TRA) for cardiac catheterization, with a reported incidence varying from 0.8%-30.0%.³ Although most cases of RAO are asymptomatic and may go undiagnosed, the fear of ischemic complications persists despite the lack of evidence that hand ischemia occurs after RAO or in the absence of a patent palmar arch.

The question of whether or not to avoid TRA for cardiac catheterization in patients without a patent palmar arch is of great importance due to evidence favoring fewer vascular complications with the transradial approach.⁴ Moreover, a compelling argument in favor of the transradial approach for cardiac catheterization is seen in patients presenting with ST-segment elevation myocardial infarction (STEMI), in whom radial access may confer a mortality benefit.⁵ The incidence of the lack of a palmar arch in patients undergoing cardiac catheterization is 6.4%-27.0%.⁶ Thus, excluding patients for radial cardiac catheterization on the basis of an absent palmar arch may expose a significant portion of patients to the higher rate of vascular and bleeding complications associated with transfemoral access, and potentially a higher rate of mortality in STEMI patients.

In this issue of the Journal of Invasive Cardiology, Maniotis and colleagues evaluate the efficacy and safety of TRA results for diagnostic coronary angiography and ad hoc angioplasty irrespective of the modified Allen’s test (MAT).⁷ This prospective, single-center observational study included 1776 consecutive patients who presented for coronary angiography and/or angioplasty (regardless of indication) between March 2011 and January 2014. A total of 1035 procedures were performed via TRA (approximately 55% of the total procedures done during the study period), with 588 procedures (56.8%) coronary angiography only and 447 procedures (43.2%) coronary angiography plus ad hoc angioplasty. The MAT was negative in 256 cases (25%) and positive in 779 cases (75%). All patients had the MAT performed (without pulse oxymeter) by five independent colleagues at the institution, with results unknown to the procedural operators. Baseline characteristics were comparable between negative and positive MAT cases. All cases were performed through a 6 Fr radial sheath, with 5 mg verapamil introduced through the sheath at the start of the case along with 5000 units of unfractionated heparin (UFH). In the case of ad hoc angioplasty, the procedural anticoagulation strategy was decided by the operator with the option of utilizing either UFH (to reach 100 U/kg patient weight) or bivalirudin (0.75 mg/kg bolus and 1.75 mg/kg/hr infusion) until the end of the procedure. All sheaths were removed at the conclusion of the procedure and hemostasis was achieved using various radial artery closing devices for 4-6 hours under a strategy of patent hemostasis attempted in all cases. Radial artery patency was assessed at discharge and if a radial pulse was not palpable, then a Doppler exam was performed to confirm the RAO.

Maniotis and colleagues reported an overall RAO rate of 6.2% in the negative MAT group versus 4.8% in the positive MAT group (P=.85).⁷ RAO was adjudicated to be clinically silent in both groups. Additionally, there was no significant difference in procedural characteristics between the negative and positive MAT groups with respect to overall procedural time (P=.33), radiation exposure (P=.24), and radial to femoral crossover rate for all procedures (P=.64). Procedural success, anticoagulation strategy, and type of P2Y12 platelet receptor antagonist used during angioplasty were all comparable between both groups. The authors also reported on post-angioplasty complications including neurologic, lost stent, perforation, tamponade, arrhythmias needing treatment, and cardiac catheterization lab deaths, all of which were uncommon and statistically comparable between negative and positive MAT groups.

What should we take away from this study? First, the rate of absence of a patent palmar arch as manifest by a negative MAT was higher than expected. Whether this represents differences in methodology used to assess the palmar arch or an intrinsic characteristic of the population studied is unclear. Barbeau and colleagues assessed palmar arch patency by plethysmography (PL) and pulse oximetry (OX) in 1010 patients and found these to be more sensitive than the MAT alone (P<.001 by McNemar’s test in 1009 patients).⁸ Furthermore, they found that by MAT alone, 6.4% of patients are excluded from right or left TRA for cardiac catheterization, whereas the exclusion rate decreased to 1.5% when PL and OX were used in combination. Thus, extrapolating the findings of Maniotis et al to clinical practice needs to be done with caution, as some of the negative MAT patients may in fact have had patent palmar arches if more sensitive methodologies were used.

Second, and notwithstanding the discussion above, the absence of any hand ischemia in their study is noteworthy, particularly in the negative MAT group. This study reinforces signals seen in other studies with respect to the overall low incidence of RAO and low to absent clinically-detectable incidence of hand ischemia after TRA for cardiac catheterization.⁹ It also supports studies failing to find a relationship between a negative MAT and hand complications including RAO or ischemia. Finally, recent studies of patients undergoing transulnar catheterization in the presence of occlusion of the ipsilateral radial artery have failed to report any hand ischemia.¹⁰ While these latter studies have been performed in only limited numbers to date, the lack of hand ischemia despite an absent palmar arch calls into question the long-held belief that “wrist” catheterization should only be performed in patients with a positive MAT.

Current guidelines and many experts recommend assessing the patency of the palmar arch prior to TRA for cardiac catheterization. There are no robust data demonstrating that prescreening patients with the MAT reduces RAO rates or hand ischemia, or is predictive of hand complications. With a growing body of literature, including the study by Maniotis et al, calling into question the value of preprocedural palmar arch patency, it is perhaps time to reevaluate this practice, rather than continue a long-held tradition with little basis in evidence. Like many long-held traditions, transitioning to a new paradigm will require more evidence that “wrist” catheterization can be performed safely independent of preprocedural palmar arch patency. Until then, the state of the arch remains in flux.

References

1. Campeau L. Percutaneous radial artery approach for coronary angiography. Cathet Cardiovasc Diagn. 1989;16:3-7.
2. Bedford RF. Radial arterial function following percutaneous cannulation with 18- and 20-gauge catheters. Anesthesiology. 1977;47:37-39.
3. Wagener JF, Rao SV. Radial artery occlusion after transradial approach to cardiac catheterization. Curr Atheroscler Rep. 2015;17:489.
4. Jolly SS, Yusuf S, Cairns J, et al. Radial versus femoral access for coronary angiography and intervention in patients with acute coronary syndromes (RIVAL): a randomised, parallel group, multicentre trial. Lancet. 2011;377:1409-1420.
5. Bernat I, Horak D, Stasek J, et al. ST-segment elevation myocardial infarction treated by radial or femoral approach in a multicenter randomized clinical trial: the STEMI-RADIAL trial. J Am Coll Cardiol. 2014;63:964-972.
6. Benit E, Vranckx P, Jaspers L, et al. Frequency of a positive modified Allen’s test in 1000 consecutive patients undergoing cardiac catheterization. Cathet Cardiovasc Diagn. 1996;38:352-354.
7. Maniotis C, Koutouzis M, Andreou C, et al. Transradial approach for cardiac catheterization in patients with negative Allen’s test. J Invasive Cardiol. 2015;27:416-420. 
8. Barbeau GR, Arsenault F, Dugas L, et al. Evaluation of the ulnopalmar arterial arches with pulse oximetry and plethysmography: comparison with the Allen’s test in 1010 patients. Am Heart J. 2014;147:489-493.
9. Barbeau GR, Gleeton O, Roy L, et al. Transradial approach for coronary interventions: procedural results and vascular complications of a series of 7049 procedures (Abstr). Circulation. 1999;100:I306.
10. Kedev S, Zafirovska B, Dharma S, Petkoska D. Safety and feasibility of transulnar catheterization when ipsilateral radial access is not available. Catheter Cardiovasc Interv. 2014;83:E51-E60.

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From the Wake Forest School of Medicine, Winston-Salem, North Carolina.

Disclosure: The authors have completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. The authors report no conflicts of interest regarding the content herein.

Address for correspondence: Robert J. Applegate, MD, FACC, FSCAI, Section of Cardiovascular Medicine, Wake Forest School of Medicine, Medical Center Boulevard, Winston-Salem, NC 27157-1045. Email: bapplega@wakehealth.edu