Although the radial artery (RA) at the wrist is preferred over the femoral artery as access for coronary angiography and percutaneous coronary interventions (PCI)1, use of the RA has several limitations: the uncomfortable position of the left arm in patients with left internal mammary graft, the need to supinate the hand, which can exacerbate chronic joint pain, the depth of the RA in large arms, which could make arterial puncture challenging even under ultrasound guidance (Figure 1), the risk of sporadic bleeding in the forearm, and the risk of RA occlusion.
In contrast, the distal radial artery (DRA) puncture site immediately above the scaphoid or trapezium bones in the hand (Figure 2) allows the arm to stay in a more natural and comfortable position for both the patient and the operator (Figure 3). The DRA ascends from a nadir in the wrist to a peak at the trapezium, before turning its course down again to dissipate in the metacarpal bones (Figure 2). The more distal the DRA, the more superficial it runs in the hand, making it readily accessible to needle puncture by ultrasound. It also lies immediately above the wrist bones, facilitating hemostasis and allowing free movement of the wrist post procedure. Use of the DRA as a default access in the catheterization laboratory could preserve the more proximal RA access for future use and could reduce the risk of hand ischemia, since the puncture site of the DRA is distal to the origin of the superficial palmar arch.
Despite these benefits, a small-caliber DRA could dissuade interventional cardiologists from attempting this technique. Contrary to the RA, limited data have been published on the size of the DRA. Using quantitative angiography, Valsecchi et al found that diameter is smaller in the DRA compared with the RA.2 Small vessel caliber could make DRA access more challenging among operators lacking experience with ultrasound visualization. Small size could also result in a higher rate of vessel spasm and occlusion from trauma inflicted during the arterial puncture and cannulation with the sheath, especially if the outer diameter of the chosen sheath is larger than the inner diameter of the DRA.
Transition to DRA Access as Part of a Quality Improvement Project
Here we describe our experience in the first 200 consecutive patients to undergo DRA access in the cardiac catheterization laboratory of Rockdale Medical Center (Conyers, Georgia)3, over half of whom had acute coronary syndrome (Figure 4). Four patients in the myocardial infarction group had cardiogenic shock. Most patients underwent diagnostic coronary angiograms, and 28% had PCI. A small number of patients (4.7%) had diagnostic lower extremity angiograms with and without revascularization using the DRA. Table 1 shows the equipment preferred in DRA patients undergoing left heart catheterization, coronary angiography of native and grafts, left ventriculography, peripheral angiography, and PCI.
Most patients undergoing DRA had the access done in the right hand (Table 2). The left DRA was selected in only 9% of the cases, when patients needed a peripheral lower extremity angiogram, had no right RA blood flow by ultrasound, or had a native coronary artery or any graft, including the left internal mammary artery (LIMA), that could not be engaged with a diagnostic or guider catheter from the right DRA. Twelve of the 200 patients required access in both DRAs to complete their procedure, either because the LIMA graft could not be engaged from the right side, or because the diagnostic or guider catheter did not engage the desired coronary artery due to a very steep angle between the innominate and the ascending aorta.
This gradual practice change, from a “radial first” approach (>80% of patients) to DRA, began in May 2017. Designed as a quality improvement project (QIP), the relocation of the puncture site to few centimeters forward from the wrist to the base of the thumb had as goals increasing patient satisfaction, reducing access-site bleeding complications, and lowering radial artery occlusion below the currently accepted rates for RA access. At the same time, Kiemeneij published the first experience with left DRA access in the western literature4, and with this came the opportunity to further refine and expand the DRA technique, with the aim of reducing vascular complications, improving patient comfort, and shortening post-procedure recovery.
We define the DRA access technique as the puncture of the RA not only in the “anatomical snuffbox” above the scaphoid, but also anywhere along the DRA trajectory across the carpal bones, before reaching the thumb. Therefore, the “DRA access technique” nomenclature is more technically inclusive than “snuffbox technique” for this approach to arterial access.
“Playground Slide” Imagery for the DRA
The surrounding DRA architecture can be envisioned as a “playground slide” in the hand (Figure 5). The DRA at the trapezium is the top of the slide, before turning to form the superficial and deep palmar arches. The “bumpy” downslope of the slide represents the DRA passage across the scaphoid and trapezium bones. The bottom of the slide forms the RA at the distal end of the radius bone at the styloid process.
This analogy of the DRA following a “playground slide” trajectory allows the physician to consider multiple opportunities to enter the DRA in the hand above the RA puncture site traditionally used. If the first access attempt at the top of the “slide” fails (DRA at the trapezium bone), further attempts can be made going down the DRA toward the scaphoid bone without harm. This DRA approach allows the operator to save the traditional RA access in the forearm as the final radial option, before considering ipsilateral ulnar, contralateral arm, or femoral arterial access.
Indeed, the curvilinear downslope of the DRA, which brings it in close contact with the carpal bones, accounts for most of the technical difficulties confronted in mastering this new technique. On the other hand, small size does not seem to be a factor, since the caliber of the DRA measured by ultrasound was not different from the caliber of the RA in our 200 patients, though women did have a smaller DRA mean lumen diameter than men (2.1 mm vs 2.4 mm respectively, P<.01), making DRA and RA access both slightly more challenging in females (Figure 6A-B).
The discrepancy between our DRA size data showing no difference with the RA size in the overall population and the data from Valsecchi2 could be explained by the different imaging modalities and the different time of measurement. Valsecchi used quantitative angiography at the time of the heart catheterization/PCI procedure, while we used noninvasive duplex ultrasound of the DRA and RA several weeks after the angiographic procedure.
DRA Crossover and Success Rate
Since the purpose of this QIP was to further improve the already acceptable rate of vascular complications of a “radial first” practice, the first 100 consecutive DRA patients were chosen based on a series of favorable clinical and anatomical factors that the operator felt would support an equal or better outcome, without compromising safety or the result of the angiographic or interventional procedure. The gradual transition from RA to DRA in 87 DRA patients over 6 months resulted in achievement of a 96% success rate. Thirteen of the first 100 patients underwent crossover from DRA to another access site (Table 3); most DRA failures were due to the inability to thread the guidewire into the DRA after encountering resistance, despite good backflow in the puncture needle.
The strategy followed in this QIP and lessons learned are summarized as follows:
- All arterial punctures should be done under ultrasound guidance, with no exception.
- The transition from RA to DRA began with DRA access in only a small fraction of cases during the first month, gradually increasing from 25% to 100% by the seventh consecutive month. Patients participating in this QIP during the first few months were stable, had a height in the 5- to 6-feet range, a palpable DRA, a strong, palpable radial pulse and blood flow by ultrasound, were undergoing non-complex elective procedures, and had a stable kidney function.
- The first 30 patients had DRA inner diameter >1.8 mm.
- The first 30 patients underwent puncture low in the “playground slide” since higher DRA access at the trapezium requires that the guidewire travel over a longer curvilinear path, resulting in more opportunity for wire resistance and higher risk of access failure.
- The guidewire should never be forced in the DRA, as it could be deflecting into a side branch or dissecting the artery.
- If the guidewire has a clot at the tip during re-entry into the needle hub during a difficult DRA access, even with good backflow, the puncture should be repeated at a position below the failed spot as the DRA is likely dissected at the entry site.
- Patients must be monitored for potential vascular complications as part of a customized hemostasis protocol.
- Educate the catheterization laboratory team and the nurses about the new access technique, and monitor outcomes and technical improvement closely.
Following the anticipated steep learning curve in our first 100 patients undergoing DRA access at Rockdale Medical Center, in the second 100 consecutive patients completed, we observed:
- Crossover from DRA to RA (n=3) or to ulnar artery (n=4) was again due to our inability to advance the guidewire into the DRA despite good backflow of blood. No patients had a crossover to femoral access.
- DRA was not attempted in one patient with known severe bilateral subclavian artery stenosis.
- DRA access was not attempted in 4 patients, because the DRA was diminutive or had no blood flow by ultrasound, or because the patient was too tall (6 feet, 4 inches); current catheters and guiders are not long enough to reach the coronary arteries from the DRA in patients generally over 6 feet, 2 inches tall or in those with a very elongated thoracic aorta.
- DRA puncture and sheath placement reached a consistent successful rate of >90% after six months of using this technique as our default access.
Among all 200 consecutive patients undergoing DRA access, there were 23 ST-elevation myocardial infarctions (STEMIs). The time to obtain DRA access in the STEMI group was <3 minutes in all patients, which is within the accepted time recommended by the 2013 Consensus Statement from the Society for Cardiovascular Angiography and Intervention’s Transradial Working Group.5 The average time from DRA sheath placement to dilating the infarct lesion in these 23 patients was 15 minutes (8-26 minutes range); four of these patients had times above the recommended 20-minute limit due to the difficulty of crossing an acute total occlusion in one patient (25 minutes) and due to the need for guide exchanges to improve guide support for PCI in three patients (23, 24, and 26 minutes).
Mastering the DRA Technique
- Patients are prepped and draped according to the standard protocol for RA access. The wrist and the hand along the thumb should be sterilized, and the sterile drape should expose the anatomical snuffbox and the base of the thumb (Figures 3 and 7).
- The right forehand near the elbow and the hand are taped to a slide board in a natural position, with the forearm and palm facing the patient’s side, without supination or extension of the hand.
- If puncture of the left DRA is needed, the left forearm and hand are left to rest over the right lower abdomen, near the right groin, in a comfortable prone position (Figure 3).
- Palpate the anatomical snuffbox with the index finger and draw a triangle on this landmark with a black pen before administering local anesthesia around this puncture site (Figure 7). Correctly identifying the scaphoid and the prominence of the trapezium bone at the outset will avoid inadvertent puncture outside the DRA pathway.
- Measure the inner lumen diameter of the DRA at the desired puncture site by ultrasound and select a sheath with an outer diameter equal or smaller than the inner lumen diameter of the artery, so the arterial/sheath size ratio (A/S) is as close to 1 as possible to minimize the risk of RA and DRA occlusions. Routine use of 5 French (Fr) sheath and 5 Fr catheters as a default practice in the catheterization laboratory has the advantage of minimizing adverse A/S ratios. Upsizing the 5 Fr to 6 Fr sheath if needed for interventional procedures is safe and simple.
- Be familiar with the sheath size options available, and their outer and inner diameters. The Prelude Ideal sheath has the advantage of not kinking when positioned in the DRA, as shown in Figure 8. The Glidesheath Slender Nitinol sheath (Terumo) can navigate very tortuous DRA, but it can kink.
- Infiltrate ~1 cc of subcutaneous 2% lidocaine at the DRA site chosen for puncture. Provide adequate intravenous sedation and analgesia before DRA puncture to minimize pain and vessel spasm.
- Puncture the DRA with a 21G x 4 cm radial needle using the anterior wall technique, since the carpal bones are immediately underneath the artery, and puncture of the periosteum causes significant pain. Consider puncturing the DRA as distal as possible, at the site of the trapezium bone first, and then go down the “slide” along the DRA track if needed (Figures 2 and 5). Obtain access under direct ultrasound guidance.
- If unable to thread or advance the guide wire through the needle despite adequate backflow of blood, gently turn the 21G needle clockwise, as the needle could be against the vessel wall in a tortuous segment. Forcing the wire in the DRA will cause pain and likely result in occlusive dissection of the artery. Dissection in one segment of the DRA can still allow you to puncture and successfully thread the guide wire above or below the failed entry site.
- Advance the sheath very slowly into the DRA, keeping the sheath wet to facilitate insertion and avoid acute and subacute pain at the entry site. Once the sheath has fully entered the DRA, the sheath valve is left naturally separated from the skin at an angle of ~30 degrees. This separation occurs due to the “playground slide” effect on the sheath, such that the distal tip of the sheath is at the nadir of the slide in the RA, and the sheath valve is at the high end of the slide (Figure 8). Avoid bending or kinking the proximal end of the sheath to facilitate unobstructed entry with catheters and guiders.
- Administer an RA cocktail of 200 µg nitroglycerin and 2.5 mg verapamil directly into the RA through the sidearm of the sheath in the DRA to minimize the risk of spasm. Administer unfractionated intravenous (IV) heparin per your institution’s protocol for diagnostic angiogram and provide additional heparin adjusted to maintain an activated clotting time (ACT) in the 250-300 second range for PCI.
- Monitor the finger pulse waveform in the ipsilateral thumb throughout the diagnostic and/or interventional procedure. Continue monitoring using finger photoplethysmography for 60 minutes after completion of uncomplicated procedures.
- The sheath in the DRA is removed immediately after completing the diagnostic or interventional procedure.
- Apply intermittent finger compression over the ipsilateral ulnar artery immediately after pulling the DRA sheath in the catheterization laboratory to promote antegrade flow through the RA and to minimize the risk of RA occlusion.6
- For diagnostic angiogram, achieve patent hemostasis of the DRA with either a Prelude Sync hemostatic device (Merit Medical) using <10 cc (Figure 9C) or finger pressure applied to the puncture site for 15 minutes (Figure 9A). If bleeding persists at the puncture site after finger compression, place a Prelude Sync compression device using <10 cc air and deflate the pressure cuff completely over a 30- to 60-minute period, as tolerated. Place the Prelude Sync hemostatic device precisely at the center of the puncture site to prevent bleeding from retrograde blood flow into the access site. With finger hemostasis, begin pressure using two fingers or the thumb to increase the area of compression and to reduce the risk of bleeding. Once hemostasis has been secured, with no bleeding from antegrade or retrograde blood flow and no oozing in the surrounding tissue around the puncture site, the operator can finish the 15-minute DRA compression with one finger.
- Demonstrate for patients how to maintain finger compression of the DRA puncture site with their own finger to stop unexpected bleeding after hemostasis has been completed by the cardiovascular team (Figure 9B). Instruct patients to call their nurse immediately if bleeding occurs after achieving hemostasis. Patients are moved out from the cardiac catheterization laboratory to the recovery room with either a Tegaderm if hemostasis is completed, or a Prelude Sync compression device at the puncture site(s) if the operator anticipates the need for a long hold or if bleeding persisted after finger hemostasis.
- For PCI, peripheral vascular interventions, and fractional flow reserve (FFR) measurement requiring higher doses of IV heparin, the Prelude Sync compression device is safe and very effective in achieving hemostasis, and it can be generally removed from the hand within 60 to 90 minutes post procedure. Use of glycoprotein IIb/IIIa antiplatelet agents (i.e., tirofiban [Aggrastat, Medicure]) in PCI requires 60-90 minutes of compression with the Prelude Sync hemostatic device with <10 cc of air.
- PCI patients with ACT <250 seconds at the end of the procedure can achieve hemostasis with finger pressure.
- All patients should leave the cardiac catheterization laboratory with palpable radial and ulnar pulses and with no oozing or bleeding from the DRA puncture site. If the radial pulse is lost post DRA access, further attempt to recover the pulse should be made in the recovery room with ulnar compression. In very rare cases, patients may be considered for long-term anticoagulation.
- Patients undergoing DRA can get out of bed and eat immediately post procedure, and they generally have no limitations on the use of their arms or hands, even if they have the Prelude Sync compression device in place.
- Stable patients undergoing diagnostic coronary angiography using the DRA access can be discharged home one hour after achieving patent hemostasis and fully recovering from conscious sedation.
Benefits of DRA Access
The DRA has the potential to become the safest and most convenient access for coronary angiography and intervention, due to its location in the hand directly above the proximal and distal row of the carpal bones (Figure 2). In contrast, the RA lays more parallel than perpendicular along the radius bone at the wrist (Figure 1A). There is no immediate transverse bone underneath the RA in the forearm or the wrist to oppose the force of the compression devices, making hemostasis post-sheath pull more vulnerable to bleeding.
Indeed, the DRA and neighboring carpal bones parallels that of the femoral artery, which lies above the head of the femur in the groin, and appears indistinguishable from femoral access, as illustrated by Duplex color ultrasound in Figure 10, though at different scales. Although both puncture sites are directly above a firm transverse bony surface, the DRA has the advantage over the femoral of providing a more effective hemostasis, since it is superficial, readily accessible by ultrasound, and ~4 times smaller in caliber than the femoral artery. The infrequently used ulnar artery access at the wrist7 is close to the ulna and adjacent to the ulnar nerve in the forearm, but is not as close above a transverse bone as the DRA.
Our first 113 consecutive patients (May-November 2017), most of whom underwent cardiac procedures for ischemic heart disease3, experienced no access-site bleeding complications using the Prelude Sync hemostatic device following DRA access, nor did the subsequent 87 consecutive patients (for a total of 200 cases), 37 of whom achieved patent hemostasis with only finger pressure for 15 minutes (Figure 9A). None of the patients undergoing hemostasis with finger pressure had any minor or major bleeding or any other vascular complication.
Reduced RA Occlusion With Post-Procedure Ultrasound Monitoring
We also found that use of DRA access at various entry points along the “slide” (Figures 2 and 5) seemed to protect the RA from occlusion. The DRA technique described here resulted in <1% RA occlusion as ascertained by follow-up hand and forearm ultrasound in 84% of patients, done at an average of 8 weeks post procedure (2 RA occlusions out of 212 DRA procedures); occlusion of the DRA was more frequent (5.2% of cases).
Vessel occlusion was minimized though multiple strategies: puncturing the DRA under direct ultrasound visualization; using the smallest sheath size for an A/S >1; using IV heparin and an intra-arterial “radial cocktail” of nitroglycerin and verapamil to minimize arterial spasm and thrombosis; and, most recently, shortening the duration of DRA compression to no more than 15 minutes with finger hemostasis.
Eight of 11 patients with A/S ratio <1 experienced DRA occlusion. Thirty-seven patients had finger hemostasis for 15 minutes post heart catheterization and PCI. Studies have shown that decreasing compression time to 15 minutes reduces RA occlusion significantly after PCI.8 In addition, our patients had routine simultaneous ulnar artery compression immediately after pulling the sheath from the DRA. The ulnar pressure was applied intermittently throughout the first 10 minutes of patent hemostasis to increase the chance of a patent RA and DRA post procedure.
Our use of DRA access with no bleeding and no ischemic complications motivated us to explore the possibility of shortening the discharge time of stable patients who had fully recovered from premedication and conscious sedation to one hour after achieving hemostasis post cardiac catheterization and peripheral vascular procedures. Selected patients with stable disease and ideal hemostasis, defined as successful patent hemostasis achieved with finger pressure for 15 minutes, can leave the hospital with a Tegaderm at the puncture site, no arm board, and no restrictions of the affected arm approximately one hour after hemostasis has been achieved in the catheterization laboratory. In contrast, current RA hemostasis protocols recommend compressing the artery with a device for approximately two hours post cardiac catheterization, with patients discharged approximately 2.5-3 hours post procedure.
Beyond this QIP study, among all patients in whom we have used DRA access since initiating this technique at our practice, 70 have had shortened hemostatic recovery time following coronary and peripheral angiograms with or without intervention and with ideal hemostasis, none of whom had any complications.
Our experience demonstrates that the DRA should be added to the contemporary arterial access options in cardiac catheterization laboratories. Preliminary results of a single operator experience at a community hospital in the U.S. demonstrate that DRA access is safe and convenient for the patient and the operator. This technique protects the RA from occlusion and may provide other unique advantages over RA access due to its proximity to the carpal bones in the hand. Use of the DRA in 200 consecutive patients resulted in no minor or major bleeding complications, no ischemic complications, and very low crossover rate to RA, ulnar, or femoral artery access sites. Use of the DRA in STEMI patients is safe and effective and meets the times to comply with current best practices for transradial angiography and intervention. Future studies should confirm the benefits of this technique, develop technology to reduce DRA occlusion, and design probabilistic models to guide access site choice in individual patients.
The author thanks Steve Einbender for his statistical assistance, Drew Imhulse from Emory Healthcare media services for his assistance with the figures, Bob Todd, RVT, for his technical assistance, and Michelle Kienholz for her editorial assistance. A sincere thanks to the entire catheterization laboratory team for helping develop this technique.
- Ferrante G, Rao SV, Juni P, et al. Radial versus femoral access for coronary interventions across the entire spectrum of patients with coronary artery disease: a meta -analysis of randomized trials. JACC Cardiovasc Interv. 2016; 9: 1419-1434.
- Valsecchi O, Vassileva A, Francesco A, et al. Early clinical experience with right and left distal transradial access in the anatomical snuffbox in 52 consecutive patients. J Invasive Cardiol. 2018; 30(6); 218-223.
- Flores EA, Todd R. Use of the distal radial artery (DRA) in the anatomical snuffbox as a default access in the cardiac catheterization laboratory [Abstract]. In: The Society for Cardiovascular Angiography and Interventions Scientific Sessions; 2018 Apr 25-28; San Diego, CA. Catheter Cardiovasc Interv. 2018; 91(Suppl 2): S218.
- Kiemeneij F. Left distal transradial access in the anatomical snuffbox for coronary angiography (ldTRA) and interventions (ldTRI). EuroIntervention. 2017; 13(7): 851-857.
- Rao S, Tremmel J, Gilchrist I, et al. Best practices for transradial angiography and intervention: a consensus statement from the society for cardiovascular angiography and interventions transradial working group. Catheter Cardiovasc Interv. 2013; 83: 228-236.
- Pancholy SB, Bernat I, Bertrand OF, et al. Prevention of radial artery occlusion after transradial catheterization: the PROPHET-II randomized trial. JACC Cardiovasc Interv. 2016; 9: 1992-1999.
- Dahal K, Rijal J, Lee J, et al. Transulnar versus transradial access for coronary angiography or percutaneous coronary intervention: a meta-analysis of randomized controlled trials. Catheter Cardiovasc Interv. 2016; 87: 857-865.
- Rathore S, Stables RH, Pauriah M, et al. Randomized clinical trial on short-time compression with Kaolin-filled pad: a new strategy to avoid early bleeding and subacute radial artery occlusion after percutaneous coronary intervention. J Interv Cardiol. 2011; 24: 65-72.
Disclosure: Dr. Flores reports no conflicts of interest regarding the content herein.
Dr. Enrique Flores can be contacted at email@example.com.