Abstract: Background. Distal transradial access in the anatomical snuffbox has advantages over standard access in terms of patient and operator comfort levels and risk of ischemia. Radial artery preservation could be a relevant issue in patients requiring multiple radial artery procedures and coronary bypass with the use of a radial graft. One relevant drawback is the challenging puncture of a small and weak artery, with a steeper learning curve. Aim. The study was aimed at proving feasibility and safety of right and left transradial access in the anatomical snuffbox. Methods. All 52 consecutive patients assigned to only one operator program underwent diagnostic or procedural intervention through distal transradial access in the anatomical snuffbox. Results. The overall feasibility was 90%, greater than expected in our early clinical experience, with 47 successful accesses out of 52 patients. Failures were due to proximal radial artery occlusion and hypoplastic/vasospastic distal radial artery. Conclusion. Distal transradial access in the anatomical snuffbox is an appealing and feasible option for both patients and operators. Further studies are needed to evaluate the clinical benefits conferred by this approach.
J INVASIVE CARDIOL 2018;30(6):218-223. Epub 2018 March 15.
Key words: anatomical snuffbox, distal radial artery, transradial approach, percutaneous coronary intervention
Ever since the introduction of radial coronary angiography by Campeau in 1989,1 the use of radial coronary angiography and percutaneous coronary intervention (PCI) has steadily increased over the past few years worldwide.
The first radial transluminal coronary angioplasty with Palmaz-Schatz stent implantation was performed by Kiemeneij in 1992, and was a milestone in invasive cardiology. Since then, advances in this technique and in the equipment used, along with the dedication of pioneering physicians, has brought the radial approach to the forefront, resulting in a paradigm shift from femoral to radial.2-4
This revolution from Campeau and Kiemeneij was the starting point for an evolution of transradial technologies with dedicated fine-access needles, hydrophilic sheaths, catheter shapes, and hemostatic devices, followed by continuous improvements in profile and deliverability of intravascular devices.
Transradial cardiac catheterization is reported to be more beneficial compared to other approaches, with easier and safer postprocedural hemostasis, better patient comfort and preference, earlier ambulation, and greater possibility of performing the procedure with same-day discharge.
The greatest benefits from the radial approach were observed in patients at the highest risk for bleeding, which includes the elderly, women, and patients with acute coronary syndromes. Many trials have proved that a transradial approach has the lowest bleeding in ST-elevation myocardial infarction patients as compared to a transfemoral approach.5,6
The transradial approach is now considered the new gold standard for vascular access in the coronary intervention field, and it’s also growing in popularity for peripheral endovascular and interventional radiology procedures.7
Despite being the default strategy for routine coronary procedures, the transradial approach has a few drawbacks. One of the most prevalent complications is radial artery occlusion (RAO), a silent complication that occurs in about 4% of patients despite proper anticoagulation.8 In addition, repeated transradial procedures may increase the occurrence of arterial occlusion, limiting this vessel’s viability as an access site for repeated procedures, particularly during urgent procedures, where benefits are more relevant.
Moreover, transradial intervention can lead to radial injury without occlusion, with a progressive narrowing of the vessel due to segmented intimal hyperplasia and endothelial dysfunction, a great concern for patients in whom the radial artery may be used as a conduit for coronary artery bypass graft. From an ergonomic and comfort perspective, patients must lie with their arm in a supine position; as a result, the operator needs to stand in a bent position for long periods. In addition, patients with various orthopedic injuries, including frozen shoulders and elbows, may be unable to flex their wrist for optimal access.
Radial artery cannulation from the dorsal aspect of the left hand in the anatomical snuffbox has been recently proposed by Kiemeneij as a possible solution to overcome some drawbacks of standard radial artery cannulation.9
This new and challenging approach can be considered a further refinement of the standard routine radial approach, aimed at providing additional vascular access-site options, better ergonomics, and preservation of the routine distal radial entry site from radial occlusion and vascular injuries.10-13 The aim of the study was to evaluate safety, feasibility, and effectiveness of right and left radial artery access in the anatomical snuffbox.
Ethical approval from the hospital committee was obtained and informed consent was a prerequisite before enrolling each subject. Patients were selected from the catheterization laboratory of Bergamo Papa Giovanni XXIII, a tertiary-care hospital, between September 2017 and November 2017.
The last patient of the day assigned to Dr Valsecchi’s operating program underwent a diagnostic or procedural intervention through the distal radial artery in the snuffbox. The choice between a right or left snuffbox approach was made by Dr Valsecchi according to his preference and taking into consideration the patient’s comfort.
The presence of both a valid pulse in the anatomical snuffbox and in the conventional forearm site was the only eligibility criteria for the study. At the beginning of the study, patients with unstable hemodynamic conditions were excluded. Due to the increased confidence of the operator, this condition was no longer considered an exclusion criteria after 20 patients.
Technical aspects of the snuffbox procedure. The left upper arm was folded over the patient’s belly toward the operator, who was standing on the right side in the case of left transradial access. The right upper arm was placed on a side board with the hand in supine position in the case of right transradial access. Contrary to other studies, the patient was not asked to grasp his thumb under the other four fingers in order to bring the snuffbox artery on the surface of the radial fossa.
After subcutaneous injection of 2-3 mL lidocaine hydrochloride through a 25 G needle, the puncture was performed using a 20 G micropuncture needle with the Seldinger’s technique. Snuffbox radial artery cannulation was considered a failure after five unsuccessful puncture attempts.
After successful artery puncture, a guidewire was smoothly advanced through the needle and used to guide the sheath through the artery. Sheath choice (5 Fr, 5/6 Fr Glidesheath Slender, or 6 Fr) was at the operator’s discretion. Fifty of the 52 cases were performed using a long radial 6 Fr hydrophilic sheath (PreludeEase hydrophilic sheath introducer; Merit Medical).
A standard radial pharmacological cocktail with 2.5 mg verapamil, 1 mL 5% lidocaine hydrochloride, and 1 mL bicarbonate was mandatory by protocol. Anterograde radial angiography with enough recording time to observe retrograde ulnar was performed in every patient at the beginning and end of the procedure (Figure 1). However, in cases of snuffbox access failure, ulnar and radial arteriography was performed at the end of the procedure. Images of the hemostatic compressive bandage are shown in Figures 2A-2C. Quantitative angiographic measurements of the snuff box artery, distal radial artery (at the level of the radial styloid), and proximal radial artery (5 cm above the radial styloid) were performed; the radial sheath was used for the calibration reference.
Statistical analysis. All analyses were performed with the Statistical Package for Social Science, version 24 (IBM). Continuous variables are reported as mean ± standard deviation. Categorical data are reported as counts and percentages. Correlations were made using Pearson’s test. Statistical data were considered significant with a P-value <.05.
Mean patient age was 68 years old, and men accounted for 82% of the population. Anthropometric characteristics were within reference values for an elderly Italian population.
Mean ejection fraction was 50 ± 7%, and 75.0% had a known/suspected ischemic cardiomyopathy with multivessel coronary disease. Right transradial coronary angiography had already been performed in 23/52 patients. Although clinical presentations of the study span the entire spectrum from stable coronary artery disease to cardiogenic shock, most of the procedures were performed in stable clinical conditions.
Radial snuffbox access was used for coronary angioplasty and following stent insertion in 25/52 patients (48.1%) without access-related limitations. Interestingly, a redo snuff-box artery approach was applied in 1 patient for a multi-staged revascularization (Figure 3). Patient and procedural characteristics are summarized in Table 1.
A 6 Fr sheath radial introducer was employed after the puncture of the snuffbox radial artery. In 2 patients with falsely presumed small radial vessel from arterial pulse, a thinner radial sheath was used for a diagnostic angiography.
Ventriculography and preprocedural and postprocedural radial angiographies were performed in all patients according to study protocol. Sones catheter (SON-II) alone with a first-line shape was set as the default for a single-catheter technique in our study, and was successful in 41/52 of the coronary angiographies. A two-strategy technique with standard coronary catheter was employed in 11 patients (5 in the right coronary artery and 6 in the left coronary). Coronary angiography characteristics are summarized in Table 2.
Left snuffbox approach was used in 11/52 patients and right snuffbox approach was used in 41/52 patients. Overall, puncture and cannulation were successful in 47/52 patients (90%). All failures were on the right side of the wrist; 2 were puncture failures due to small vessel diameter (hypoplastic snuffbox artery), 1 was a failed puncture-mediated spasm, and 2 were related to an unnoticed proximal radial artery occlusion with subsequent inability to wire the vessel (a palpable pulse, an eligibility criteria of the study, does not exclude radial artery occlusion in the presence of collaterals) (Figures 1G-1I). As expected, the snuffbox artery was smaller than the proximal radial and ulnar vessels on quantitative coronary angiography, without any significant correlation between snuffbox and radial/ulnar diameters. In particular, there were no correlations between snuffbox and ulnar artery diameter. (R=-.03; P=.80) (Table 3).
In our early experience, distal radial artery access in the snuffbox was successful in 47/52 patients, with an overall feasibility of 90%. Considering failure due to radial artery occlusion, not discernible by radial pulse, the overall success rate rose to 94% (47/50 patients), with a previous right radial cannulation in 44% of the patients. No complications have been reported. According to the prespecified study methods, the choice between right and left access was made by the operator according to his and the patient’s preferences. Due to the operator’s preference for the right approach, more right snuffbox arteries than left were included in the study. Kiemeneij recently reported his experience with the left distal transradial access in the anatomical snuffbox. In his work, 70/118 patients underwent distal transradial access, other patients were excluded on the basis of a weak pulse in the anatomical snuffbox and other logistical reasons (such as presence of an indwelling cannula near the snuffbox, left handedness, and patient preference for several reasons). However, in our study, a weak pulse was not a criteria for exclusion; therefore, the procedure was feasible in patients with a weak pulse.9
Potential advantages of snuffbox artery cannulation have been previously reported by Kiemeneij, and are confirmed in this study. The arm position during the intervention, especially for left access, is comfortable for the patients, who do not have to expose the palmar side of the arm. Moreover, patients with orthopedic limitations who are unable to supinate their arm can benefit from this new snuffbox approach. From a radial perspective, the snuffbox approach increases comfort for patients, allows radial access in patient with limited arm motion, and can be safely used in patients with a previous radial access. In this view, anatomical snuffbox access can be used to preserve the oft-used radial artery and limits a potential radial artery occlusion. Radial endothelial dysfunction and damage derived from repeated punctures and cannulations are also limited.
Other potential advantages of the snuffbox approach are due to the anatomical features being supplied by palmar collaterals; if there is no anatomical variance, it is a safe entry point and risk of ischemia is limited. Further studies are needed to prove this access can prevent or limit hand numbness after transradial catheterization from injury of the superficial radial nerve.
In the case of critical care patients, such as in our patient with a peripheral femoral extracorporeal membrane oxygenation device and a radial line pressure, snuffbox access was the last resourceful “out of the box” access point to avoid a femoral procedure (Figures 2E and 2F).
Another aspect that will demand further investigation is the use of snuffbox arteries as potential sites for retrograde recanalization of radial artery occlusion; a few case reports suggest that this option is feasible. Snuffbox radial access could also be advantageous in two other clinical scenarios, ie, coronary angiography in patients undergoing coronary artery bypass with the need of radial artery as a conduit and end-stage kidney disease patients with the need for a radial arteriovenous fistulas for dialysis.
The snuffbox technique does have a few drawbacks. First, the snuffbox radial artery is smaller and there is a greater risk of puncture-mediated vasospasm. Second, Yonetsu et al14 have used optical coherence tomography to demonstrate that conventional radial artery access is associated with intimal tears in acute and chronic intimal thickening; however, the significance of this finding on the outcomes of radial grafting and arteriovenous fistulas is unknown (more and more are used in the era of total arterial revascularization). Last, the short length of a typical radial catheter is an important drawback to the snuffbox technique. In fact, radial catheters are specifically designed for a classical radial artery entry site near the styloid process. Given that the snuffbox artery is 5 cm below the common radial entry site, these catheters may therefore be too short, and operators may have to perform coronary angiography or angioplasty “on the tip” of the catheter. This issue could be even more challenging in taller patients, where snuffbox artery access might be ineffective.15
Study limitations. This is a single-center study, and all procedures were performed by a single operator with vast experience in radial access (more than 15,000 radial procedures performed). The lack of a control group in our early experience with this new access technique limits our assumptions.
Distal radial artery access in the snuffbox can be another arrow in the quiver of the interventional cardiologist, and is an attractive and feasible option for both patients and operators. Further studies are needed to determine whether a more difficult technique is worth the advantages of greater patient comfort and potential radial artery preservation.
Acknowledgments. We thank our radiology technicians: Dr Sarah Vangestel, Dr Poli Ilaria, and Dr Bergamini Luciana.
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From the Interventional Cath Lab, Cardiovascular Department, Papa Giovanni XXIII Hospital, Bergamo, Italy.
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.
Manuscript submitted December 30, 2017, and accepted January 11, 2018.
Address for correspondence: A.F. Cereda, MD, Interventional Cath Lab, Cardiovascular Department, Papa Giovanni XXIII Hospital, Piazza OMS 1, 24127 Bergamo
Italy. Email: email@example.com