Radial Access for Neurovascular Procedures

Abstract

Radial access is increasingly being considered in neurovascular procedures after becoming the standard access route in percutaneous cardiovascular interventions. Current barriers include a lack of dedicated equipment for radial to neurovascular target vessels, lack of training for physicians and fellows, and physician bias toward femoral access secondary to greater experience and familiarity. Radial access has been proven to be safer and the preferred access route by most patients. These two factors make radial access inevitability when the aforementioned barriers are overcome. The purpose of this brief article is to highlight some important considerations of radial access specific to the neurovasculature.

Radial access is increasingly being considered in neurovascular procedures after becoming the standard access route in percutaneous cardiovascular interventions. ¹ Current barriers include a lack of dedicated equipment for radial to neurovascular target vessels, lack of training for physicians and fellows, and physician bias toward femoral access secondary to greater experience and familiarity.

Radial access has been proven to be safer and the preferred access route by most patients. ^{1 2 3 4 5 6 7 8} These two factors make radial access inevitability when the aforementioned barriers are overcome. The purpose of this brief article is to highlight some important considerations of radial access specific to the neurovasculature.

Beyond this article, there are several resources to consider taking advantage of including:

1. Industry-sponsored radial access courses offered by most larger companies currently manufacturing radial sheaths.

2. Leveraging experience from other physicians/staff performing radial access at your institution to standardize patient preparation and postprocedural care.

3. Reaching out to high-volume physicians for their advice and mentorship (radial community is very supportive and most are willing to share their expertise).

Rationale for Radial Access

Safety—Complications and MACE

Better safety profile of radial access in regard to access site, major bleeding, death, and major cardiac events have been well described in the cardiac literature. Although there are no randomized control trials for radial access in the neurovascular literature, there is a growing body of series describing single-center experiences and favorable outcomes using radial access for both diagnostic and interventional neurovascular procedures. ^{9 10 11 12 13 14 15 16 17 18}

A meta-analysis from Ruiz-Rodriguez et al summarized outcomes for radial versus femoral access for patients with acute coronary syndrome and included randomized control studies and cohort studies with a total of 44,854 patients between 1998 and 2014. They found statistically lower rates ( p  < 0.001) for major bleeding (1.4 vs. 3.2%), access site complications (1.2 vs. 3.6%), mortality (2.1 vs. 3.4%), and major cardiac event (5 vs. 7.2%). ¹⁹

The most frequent concern that femoral operators have is the risk of hand ischemia due to the small size of the radial artery. Although the forearm has three main arteries (radial, ulnar, and interosseous), the collateral circulation to the arm is extensive due to the deep and superficial palmar arch. Hand ischemia secondary to procedure-related compromise of the radial artery is exceedingly rare and limited to case reports. Many distal complications are embolic in nature secondary to inadvertent injection of air or particles in the sheath.

Benefits for Patients

Some potential advantages for patients include shorter preprocedural preparation and shorter procedure room times, less discomfort postprocedure (lower rates of clinically significant hematomas), less embarrassment (not exposing groin), less stress, earlier mobilization/discharge, and earlier time to eat and drink postprocedure.

Patient preference for radial access over femoral access has been described and published by our group in 2017. ⁵ Patients found radial access to be less stressful, less embarrassing, less painful intraprocedurally and postprocedurally, and had a near unanimous preference for radial over femoral access. Fig. 1 depicts the subjective responses and advantageous outcomes of radial over femoral access.

Fig. 1.

Subjective patient responses and preferences for radial versus femoral access. ⁵

Potential Cost Savings: Complications

Cost savings for radial over femoral access can be divided into indirect and direct costs to the institution and patient. In regard to indirect costs, radial access for outpatient cerebral angiography is associated with shorter preprocedural preparation times, shorter room times (rapid hemostasis with use of radial access closure devices with the advent of “radial lounges”), and shorter recover times with earlier discharge and, ultimately, shorter length of stay.

In the cardiology literature, the cost of uncomplicated radial versus femoral diagnostic coronary angiography does not significantly differ. ²⁰ However, in interventional coronary procedures or in the setting of access site complications, the costs are significantly higher. ^{21 22 23} Similar cost savings could be realized in cerebral angiography and cerebrovascular intervention as well, although this has not yet been well studied or reported.

Patient Selection

Relative contraindications to radial access include end-stage renal disease and potential need for future arteriovenous fistula, patients who may need a radial artery donor site for coronary artery bypass graft surgery, and patients with known distal arterial occlusive disease or history of Raynaud's syndrome.

Routine testing for collateral circulation is no longer recommended by most operators and by the September 2018 AHA scientific update on best practice for transradial coronary angiography and intervention. ¹ The rationale behind this recommendation is that routine use of noninvasive testing for hand collaterals with a modified Allen or Barbeau test does not predict adverse outcomes for radial access and, therefore, should not routinely be used.

Procedure planning should take into consideration the ideal construct to perform the procedure (coaxial, triaxial, need for additional support) and patient-specific factors (radial artery size, arch configuration, and cervical tortuosity). The final procedural construct should be adequate to perform the index procedure, while being appropriate for the patient to maximize success and minimize risk of complications. In certain instances, radial access may not be suitable and alternative access sites should be considered.

Patient Preparation/Positioning

Although not required, use of a dedicated radial access arm board can improve patient comfort, improve operator comfort, simplify/shorten patient preparation, and result in greater procedural success. Radial arm boards come in a variety of designs and configurations including right and left radial approach, dedicated methods to secure the wrist, and varying degrees of radiation protection ( Fig. 2 ).

Fig. 2.

( a ) A schematic representation of the Elevate Armboard (Model 8100) with proprietary integrating single-use mBrace 4250 wrist support (Advanced Vascular Dynamics, Milwaukie, OR). ( b ) Elevate Armboard with disposable towel secured to foam arm splint as wrist support. This figure also depicts the basic arm positioning with the use of a disposable towel and foam arm splint that is routinely used in our laboratory. Of note, positioning the arm board as low toward the bottom of the table and as tight to the table as possible allows for a lateral fluoroscopy tube to be brought as close to the patient's shoulder as possible. For standard radial or ulnar access, the wrist can be slightly extended and secured to the foam board. In patients with distal radial access, the hand and arm can be kept in a more anatomic position to facilitate access and maximize patient comfort.

Keys to Radial Access Success

Patient education prior to the interventional suite, including a detailed description of the procedure, often helps minimize patient anxiety. In turn, this control of expectations and anxiety helps minimize associated radial artery spasm. Additionally, approximately 1 hour prior to the procedure, 2 to 3 mL of a topical analgesia cream (Emla cream; emulsion of lidocaine 2.5% and prilocaine 2.5; AB Astra Pharmaceuticals, Westborough, MA) is applied to the expected radial access site and covered with a Tegaderm. Intravenous conscious sedation is also given based on the patient's level of anxiety and baseline vital signs.

Routine use of real-time ultrasound guidance for single-wall radial access is strongly recommended. Although many experienced radial operators use palpation and a double-wall puncture technique, ultrasound guidance for radial access generally results in shorter access times, fewer attempts, higher success rates, and fewer hematomas. The advantages of ultrasound access have been confirmed in both a randomized trial and retrospective meta-analysis of randomized trials by Seto et al and Tang et al with 1,182 combined patients. ^{24 25} The benefit of ultrasound-guided access was seen over a range of patient subgroups including the presence of peripheral vascular disease, high or low BMI, use of single- or double-wall technique and regardless of gender.

In addition to the EMLA cream, a combination of nitroglycerin (400 µg) and 1 mL buffered lidocaine is subcutaneously injected over the anticipated radial access site for analgesia and can improve procedural success and minimize radial artery occlusion (RAO; Fig. 3a ). Candemir et al described use of subcutaneous injection of 500 µg of nitroglycerin prior to radial access and found that the average size of the radial artery was larger (on average 0.5 mm) and rates of radial artery spasm were lowered (although not meeting statistical significance). ²⁶

Fig. 3.

( a ) Transverse duplex ultrasound image of distal radial artery (yellow circle) with overlying subcutaneous mixture of lidocaine and nitroglycerin (blue border). ( b ) Ultrasound probe at 45 degrees for initial skin entry which is fanned to 90 degrees (arrow) as needle is advanced to the border of the radial artery. ( c ) Indentation of the radial artery lumen (arrow) prior to single-wall puncture for access.

Use of meticulous technique and real-time ultrasound guidance will result in improved patient experience, fewer access attempts, and minimum spasm while maximizing procedural success ( Fig. 3b, c ). Expertise with ultrasound allows rapid assessment of radial artery diameter (allowing appropriately sized devices to be used) and facilitates an easier transition to alternative arm access sites including ulnar and distal radial or snuffbox access.

Routine use of a radial cocktail composed of vasodilators and systemic anticoagulation is considered standard of care in radial access procedures. Per 2018 AHA scientific update on best practice for transradial coronary angiography and intervention, a combination of calcium channel blockers (verapamil 2.5–5 mg or nicardipine 250–500 µg) and nitroglycerin (100–200 µg) is recommended to minimize radial artery spasm and potentially help minimize RAO postprocedure. ¹ Anticoagulation can be administered intra-arterial or intravenous (heparin 50 U/kg with max 5,000 U) and some operators prefer administration after successful navigation to the level of the aortic arch in case access failure is encountered and alternative access is necessary.

After successful placement of the smallest required radial access sheath or guide, routine use of radial angiography is recommended to identify variant anatomy (radial loop or anomalous origin from the brachial or axillary artery) and facilitate/expedite navigation from the forearm into the brachial artery ( Fig. 4 ).

Fig. 4.

( a ) Most common upper extremity arterial anatomy with radial, interosseus, and ulnar arteries. ( b ) Variant radial artery loop near the antecubital fossa (arrow). ( c ) High origin of the radial artery from the axillary artery (arrow) with radial artery loop in the upper arm.

Procedure-Specific Radial Access Setup Considerations

Diagnostic Cerebral Angiography

After ultrasound evaluation of the radial artery, a sheath is selected that is ideally smaller than the diameter of the radial artery. Often distal radial or snuffbox radial access can be used for diagnostic procedures, especially in patients who will likely need an additional interventional procedure in a short period of time, to preserve the standard radial access site. Use of radial-specific sheaths and hydrophilic-coated wires is the standard of care and allows for smaller outer diameters, faster access, less spasm, less patient discomfort, and lower rates of RAO. ¹

In patients with adequate radial artery diameters, our standard approach is to use a Terumo Glidesheath Slender 5F (Terumo, Tokyo, Japan) and 5-Fr Simmons-2 diagnostic catheter with an 0.038-in inner diameter to allow easy transition to a coaxial microcatheter system if faced with difficultly while selecting a vessel (most commonly left internal and left vertebral arteries). We recommend continuous flush to the radial sheath as well as continuous flush to a rotating hemostatic valve connected to the diagnostic catheter along with an 0.035-in Glidewire (Terumo).

Forming a Simmons-2 Catheter

A basic skill required for efficient cerebral angiography is the ability to form a Simmons-2 (or Simmons-3) catheter. There are three basic techniques that can be employed in subsequent order as needed. The first is to advance the wire into the descending thoracic aorta, and advance the Simmons catheter to the point where the inferior bend of the catheter is at the junction of the innominate artery/aortic arch. The wire is then pulled back to the level of the subclavian artery and the diagnostic catheter will automatically start to form a secondary curve. At this point, the Simmons catheter can be slowly advanced and rotated allowing the secondary curve to form in the ascending aorta. A second technique is to advance the wire around the aortic valve (watching for atrial irritation on the cardiac monitor) and then simply track the catheter around the wire to reform the shape. Finally, if the right common carotid or right vertebral artery is selected, the Simmons-2 catheter can be formed by withdrawing the wire and pushing the catheter forward.

Selective Catheterization of the Left Internal Carotid Artery and Left Vertebral Artery

In a large series of 1,240 patients from Korea described by Jo et al, there was a 17.6% failure of selective catheterization of the left internal carotid artery and 47.8% failure of the left vertebral artery. ²⁷ We have found this to be a major reason that many interventionalists become frustrated and abandon routine use of radial access for the cerebrovasculature. To overcome these challenges and given the fact that we do not have dedicated radial-specific catheters, we recommend use of a coaxial microcatheter that has a pressure rating and inner diameter that can accommodate forceful hand injections or power injections for 3D rotational angiograms. A coaxial microcatheter up to 2.7 to 2.8 Fr can easily be accommodated in the 0.038-in 5-Fr diagnostic catheter. Routine use of a continuous flush system and rotating hemostatic valve allows rapid conversion to a coaxial system with minimal delay. These microcatheters can be advanced over a 0.025-in Glidewire (Terumo) rather than a more expensive nitinol microwire to contain cost. If only a left vertebral injection is needed (follow-up angiography), then left radial access simplifies the procedure with a vertebral or Berenstein angled catheter shape.

Cerebrovascular Intervention

Most cerebrovascular interventions (except stroke—see later) can be performed through a 6-Fr guide catheter with an inner diameter of 0.070 or 0.071 in. Most patients have a radial artery diameter larger than a 6-Fr slender radial sheath (2.44 mm) and routine use of a 6-Fr radial sheath with a 6-Fr neuro guiding catheter provides adequate support, minimal trauma to the radial artery, and high technical success. Two important considerations are in patients with small radial artery diameters and distal radial/snuffbox access. In small radial arteries, the ulnar access maybe considered as an alternative access, although there is a learning curve and technical considerations (deeper location, adjacent ulnar nerve, and potentially more challenging hemostasis). Another approach to a small radial artery is direct access with the guiding catheter after initial access is obtained with a 4-Fr micropuncture system (see “Stroke Intervention” section). When direct radial access is performed, it is important to create a generous skin nick and use an obturator or 5-Fr diagnostic catheter within the 6-Fr guide catheter to minimize the shelf during the arterial access. Direct access may result in more spasm (especially in an awake patient); so, adequate sedation and intra-arterial vasodilators are required. Catheter manipulation should be minimized during the procedure (rotation and excessive advancement/withdrawal). Distal radial access of the left anterior circulation (left internal carotid artery territory) in larger patients may be limited by catheter lengths; so, longer guide catheters (100–110 cm) should be considered if available ( Figs. 5 and 6 ).

Fig. 5.

A 6-Fr radial access example for neurovascular intervention. This example is for a triaxial approach used for delivery of a pipeline flow diverting stent (Medtronic, Minneapolis, MN); however, a coaxial approach using just a neuro guide catheter (0.070–0.071) system can be used for two microcatheters in stent-assisted coiling or balloon-assisted coiling.

Fig. 6.

( a ) A 5-Fr diagnostic catheter (arrow) is used to select the high cervical/horizontal petrous right internal carotid artery and a 260-cm wire is used for subsequent exchange. ( b ) After exchanging the short radial sheath for direct access with a neuro guide catheter (0.088–0.091 in inner diameter), the guide is advanced to the proximal right subclavian artery with the provided obturator (arrow). ( c ) Once the turn is made from the subclavian artery into the cervical ICA, the obturator is exchanged for an intermediate catheter (aspiration catheter).

Stroke Intervention

Radial access for stroke intervention has some important considerations that the operator should be familiar with and careful patient selection is important to minimize delays to revascularization (see Table 1 ).

Table 1. Radial access stroke ^a .

Favorable	Unfavorable
1. Posterior circulation	1. LICA: type 1 arch
2. RICA: type 2/3 arch	2. LICA: type 2/3 arch with marked subclavian/innominate tortuosity
3. “Bovine arch”	3. Arch variants
4. Large patient/male	4. Small patient/female
5. Received IV tPA/on NOAC
6. Occlusive aorto-iliac disease

Abbreviations: IV, intravenous; LICA, left internal carotid artery; NOAC, non-vitamin K antagonist oral anticoagulants; RICA, right internal carotid artery; tPA, tissue plasminogen activator.

^aLimitation: Cannot use balloon guide.

Primary use of radial access should only be considered in operators and laboratories with “sufficient experience” with elective diagnostic and interventional cerebrovascular procedures. This experience will vary for individual operators, as there is a learning curve for radial expertise, commonly reported as requiring 50 cases, ideally consecutive. ²⁸ We suggest a minimum of 50 diagnostic and 25 interventional procedures as a reasonable target. Radial access (or direct carotid) is considered a reasonable alternative in stroke intervention after 20 to 30 minutes of access failure via the traditional femoral approach.

As summarized in Table 1 , patients with target vessels involving the posterior circulation, right anterior circulation (with tortuous subclavian or type II/III arches), or left anterior circulation with bovine arch configuration have anatomy that facilitates radial access. Careful evaluation of prior studies/angiograms and review of preprocedural computed tomography angiography (CTA) of the neck is paramount in good patient selection (important to perform CTA of the neck with CTA of the head as part of a routine stroke protocol).

Technical Considerations: Transradial Stroke Intervention

After evaluation of the radial artery with ultrasound, 4-Fr micropuncture access is obtained. A radial angiogram is performed to assess suitable anatomy and patency. A blood sample is drawn for baseline ACT and intra-arterial vasodilators are administered (nitroglycerine and verapamil/Cardene diluted to 20 mL of the patient's blood to minimize discomfort upon administration). Heparin is usually held until a guiding catheter is successfully positioned in the distal subclavian artery in case conversion to an alternative access is required (carotid or femoral). The micropuncture sheath is exchanged for direct access over a 180 to 260 cm Glidewire for a neuro guiding catheter (0.088–0.091 in inner diameter) which is an 8 Fr outer diameter or 2.6 mm. As in direct radial access with a 0.071-in guiding catheter, use of a generous skin nick and the obturator to minimize radial artery trauma is required. We recommend using a radial artery road map to guide navigation of the Glidewire into the subclavian artery and fluoroscopic guidance when advancing the neuro guide catheter across the elbow joint where the radial artery meets the brachial artery and represents the most common site of tortuosity. Any difficulty advancing the system should prompt care and trigger the operator to critically evaluate the radial angiogram to avoid complications such as radial artery dissection/perforation. See Figs. 6 and 7 for typical setup for stroke interventions using a radial approach.

Fig. 7.

Typical stroke intervention setup. (1) Direct radial access with neuro sheath (0.088–0.091 in), (2) aspiration catheter, (3) stent retriever, (4a) line for continuous pump aspiration during stent/aspiration catheter withdrawal, (4b) syringe aspiration for guide during stent/aspiration catheter withdrawal.

Once the guide catheters are advanced as far as possible into the carotid (internal or common carotid depending on patient/catheter lengths) or vertebral artery, standard triaxial stroke intervention can be performed.

Careful attention to hemostasis postprocedure is critical due to the size of the access, increased concerns of bleeding with tissue plasminogen activator and heparin on board, and patient movement potentially complicating hemostasis if the procedure was performed while awake. In some cases, we have found that placing a second radial compression band above the first is required to obtain hemostasis.

Managing Most Common/Major Complications

1. Spasm.

2. Vessel perforation.

3. Retained catheter.

4. Radial artery occlusion.

5. Radial artery pseudoaneurysm.

Potential complications of the radial approach should be predicted and avoided if possible. Radial artery spasm is the most common problem encountered with radial access. Adequate sedation as well as regular administration of the aforementioned radial artery cocktail is critical. In the event of presumed radial artery spasm, it is key for the operator to be patient/calm and not attempt forceful maneuvers of the catheter. Warmth to the forearm and additional sedation can be provided to aid in control of the patient's anxiety and relaxation of the radial artery. An additional dose of vasodilatory medications including nitroglycerin, verapamil, or nifedipine can be given through the sheath and has been proven to reduce radial artery vasospasm. ²⁹ With persistent spasm, subcutaneous nitroglycerin can be injected along the radial artery (without significant associated systemic effects of nitroglycerin in contradistinction to nitroglycerin paste). Transient occlusion of the ulnar artery can be performed to divert flow down to the spastic radial artery. Finally, in extreme cases, MAC anesthesia can be considered to completely relax the patient and relieve radial artery spasm. Patience is key throughout the process of management of radial artery spasm.

The operator should also be familiar with anatomic variants of the radial artery (see Fig. 4 ). The majority of variants can be navigated safely without any major concern. The key is to recognize the variant and safely proceed to avoid inadvertent injury or perforation of the vessel. The two most commonly encountered variants are radial loops and high radial insertion (origin of the radial artery from the brachial or axillary arteries).

If wire perforation of the radial artery is suspected, this should prompt immediate performance of a radial angiogram. The simplest method to control bleeding is advancement of a catheter (diagnostic or guide sheath) across the perforation; alternatively temporary balloon inflation can be employed for tamponade. If an expanding forearm hematoma is encountered, application and inflation of a blood pressure cuff, 20 mm above the systolic pressure for 10 minutes, can be performed with reversal of anticoagulation and subsequent reassessment. If this maneuver fails, there is risk of compartment syndrome heralded by loss of strength, sensation, and pulse in the distal digits which necessitates urgent vascular surgery consultation for potential fasciotomy and decompression. ³⁰

RAO is almost always asymptomatic with rates that vary according to a center's procedural volume and the operator's experience. A meta-analysis of 66 studies found RAO rates of 11% with a 6-Fr sheath and only 2% with a 5-Fr sheath, obviating the use of the smallest caliber sheath necessary for the intended procedure. ³¹ Pancholy et al found overall RAO rates at 30 days to range from 1 to 3%. ³² The primary concern with RAO is loss of the access route for future procedures. Meticulous attention to detail to minimize attempts (detailed earlier), use of radial-specific sheaths/guides, use of radial cocktail, systemic heparinization, and appropriate sizing of the devices will minimize the risk of RAO. ^{31 33} The Prophet II trial demonstrated lower rates of RAO can be achieved with ulnar counter compression in addition to patent radial hemostasis. ³² If early postprocedural RAO is detected prior to discharge for outpatient procedures, a 1-month duration of oral anticoagulation has been reported to improve rates of recanalization.

Radial artery pseudoaneurysm can be seen in patients and can be managed conservatively (small) or with prolonged placement of radial compression band, ultrasound-guided compression, thrombin injection, surgical repair, and endovascular techniques (described in case reports).

Closure

Upon completion of the procedure, hemostasis should be obtained at the radial artery access site with a patent hemostasis technique. Sufficient compression of the radial artery to control bleeding should be balanced with patency of the lumen to maintain antegrade flow as excessive radial artery pressure can result in RAO. ^{34 35} Gentle manual compression can be held for 15 to 20 minutes at the access site upon removal of the sheath. Multiple radial compression devices exist to facilitate patent hemostasis and achieve hemostasis. The TR Band (Terumo) and PreludeSync (Merit, Malvern, PA) utilize a balloon attached to a band to provide compression while the VasoStat (Forge Medical, Bethlehem, PA) produces focused compression to the radial arteriotomy utilizing a ratcheting pressure mechanism. These devices can be applied postprocedurally to provide effective patent hemostasis while the patient is moved to the holding area and preparations can be made for the next patient in the angiography suite. If RAO is recognized upon removal of the radial hemostasis device, transient compression of the ipsilateral ulnar artery can aid in the recanalization of the occluded radial artery. ³⁶

Future Directions

As “radialist”/neurointerventionalists continue to publish their experiences and outcomes, the training should also continue to grow. Articles and book chapters detailing basic radial access to advanced procedure-specific descriptions are available in the literature. A multitude of radial access online and live training courses exist for cardiology and body interventional procedures, and are beginning to spread into neurointerventional meetings as well. Industry partners have also been very supportive by providing radial access simulators for centers interested in pursuing dedicated training. Our group has also developed a dedicated training Web site for radial access in neurovascular procedures ( www.neuroradialaccess.com ). No matter the route, we should strive to start training from the residency/fellowship level and continue to spread the knowledge to all of our experienced colleagues late in practice as well.

Designated Equipment

Although radial artery access for diagnostic and therapeutic body and neurointerventional procedures has not been adopted as widely as for coronary procedures just yet, industry partners are aiding in the process with the advent of newer dedicated radial access devices. Glideslender sheaths (Terumo), with dedicated lower profile construction for the radial artery, now come in 5, 6, and 7 Fr. In addition, longer slender destination sheaths (Terumo) are now available allowing for low-profile stable 6- and 7-Fr platforms in 120 and 150 cm lengths.

Conclusions

The cardiology and body interventional literature has shown radial access to offer a variety of advantages over traditional transfemoral access including safety benefits such as lower bleeding/vascular complications and mortality, ^{2 3 4 19} lower costs related to several factors, ²⁰ as well as improved patient satisfaction. ^{6 7 8} The same benefits are now being realized in the cerebrovascular literature and thus radial access for neurointerventional procedures is an inevitable paradigm shift. As the training and experience continues to grow, radial access should be embraced and adopted into the toolbox of every practicing neurointerventionalist.