Background The transradial approach (TRA) has gained increasing popularity for neuroendovascular procedures. However, the experience with TRA in neuroangiography is still in early stages in most centers, and the safety and feasibility of this approach have not been well established. The purpose of this study is to report the safety and feasibility of TRA for neuroendovascular procedures.
Methods We reviewed charts from six institutions in the USA to include consecutive patients who underwent diagnostic or interventional neuroendovascular procedures through TRA from July 2018 to July 2019. Collected data included baseline characteristics, procedural variables, complications, and whether there was a crossover to transfemoral access.
Results A total of 2203 patients were included in the study (age 56.1±15.2, 60.8% women). Of these, 1697 (77%) patients underwent diagnostic procedures and 506 (23%) underwent interventional procedures. Successfully completed procedures included aneurysm coiling (n=97), flow diversion (n=89), stent-assisted coiling (n=57), balloon-assisted coiling (n=19), and stroke thrombectomy (n=76). Crossover to femoral access was required in 114 (5.2%). There were no major complications related to the radial access site. Minor complications related to access site were seen in 14 (0.6%) patients.
Conclusion In this early stage of transforming to the ‘radial-first’ approach for neuroendovascular procedures, TRA was safe with low complication rates for both diagnostic and interventional procedures. A wide range of procedures were completed successfully using TRA.
- arteriovenous malformation
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In recent years, various neuroendovascular procedures have become the standard of care for multiple disorders including ischemic stroke and cerebral aneurysms.1–3 The transradial approach (TRA) has been adopted by cardiology for most coronary procedures given lower complication rates, lower cost, and improved patient satisfaction compared with transfemoral access (TFA).4–6 However, it is still not widely used in the neuroendovascular world. More efforts have recently been made to adopt the ‘radial first’ approach in neuroendovascular procedures to minimize the morbidity and mortality related to the femoral access site complications.7 Early experience from different centers has shown that TRA is safe and associated with higher patient satisfaction.7 8 In addition, recent studies have shown that adopting the ‘radial first’ approach for neuroendovascular procedures can be achieved with a high level of efficacy and safety within a few weeks and after performing 50–100 procedures.8–11
TRA offers important advantages in neuroendovascular procedures compared with TFA, especially in patients with emergent large vessel occlusion in the posterior circulation, patients with complex iliofemoral anatomy, pregnant patients, and patients with aortic dissection.12–16 Other essential benefits of TRA include early mobilization and lower access-related complications, including bleeding and hematoma.17–19
In this study we assess the safety and feasibility of incorporating TRA for both diagnostic and interventional procedures using data from multiple high-volume centers. In addition, we discuss lessons learned during this transition.
We reviewed the prospectively maintained registries from six neuroendovascular centers located in the USA. We included consecutive patients who underwent neuroendovascular procedures (diagnostic and interventional) using TRA as the first-line approach between July 2018 and July 2019. We excluded all cases in whom TRA was attempted as a salvage approach after failing other access sites. Data from all sites were curated and analyzed at one of the study sites. The institutional review board at each site approved this study.
Outcomes and covariates
Our primary outcome was the success in achieving the predefined goal of each procedure. Secondary outcomes included the rate of crossover to TFA and complications related to the access site. Other variables collected included age, sex, date, the indication of the procedure, sheath size, antispasmodic regimen, heparin dose, catheter and wire type, number of catheters and wires used, duration of the procedure, radiation dose, and vessels selected. We classified complications related to access into minor (hematoma, infection, dissection, significant vasospasm, pseudoaneurysm) and major (perforation, compartment syndrome).20
Procedural protocol and technique
The arterial puncture was attempted or obtained using ultrasonography (US) with the traditional Seldinger technique (through-and-through puncture).21 Vascular access was achieved through the right radial artery in the forearm except in the following situations: (1) ulnar artery access was obtained if the radial artery radius was small on US, or there was difficulty accessing the radial artery; (2) left radial artery access was used if the radiuses of both right radial and right ulnar arteries were small on the US, or if the target vessel was in the distribution of the left vertebral artery and per operator preference; (3) radial artery access was obtained in the anatomical snuffbox for diagnostic procedures per operator preference.
A 5 Fr or 6 Fr sheath was used for diagnostic procedures and a 6 Fr or 7 Fr sheath was used for most interventional procedures. An 8 Fr sheath was used in a limited number of procedures (n=2). Between 2000 and 5000 units of heparin were administered intra-arterially or intravenously immediately after obtaining access. Interventional cases received intermittent boluses of intravenous heparin to maintain an activating clotting time of 2–2.5 times the patient’s baseline. An intra-arterial antispasmodic medication was given in most procedures (except 36 cases). Control angiography of the radial artery was performed after obtaining access in all cases. Hemostasis post-procedure was achieved using a radial closure device. All patients were examined following the procedure and prior to discharge, and all had a palpable pulse at the site of access.
TFA obtained in patients who failed TRA. TRA failure was categorized into four stages:
Stage I: Inability to insert the sheath (secondary to small radial artery radius, no return of blood following the arterial puncture, inability to advance the wire due to vasospasm, or atherosclerotic plaque, etc).
Stage II: The sheath is in the radial artery but the operator is unable to advance the guidewire or the catheter (secondary to radial artery tortuosity, vasospasm, loop, etc).
Stage III: The guidewire and the catheter reached the supra-aortic arch but the operator is unable to select one of the main supra-aortic branches.
Stage IV: The operator is able to select the target main supra-aortic branch but is unable to complete the procedure successfully using TRA.
Descriptive statistics were used to report patient demographics and clinical characteristics in the included patients. The analysis was conducted using SPSS software version 25 (IBM Corporation, New York, USA).
Anonymized data not published within this article will be made available by request from any qualified investigator. Investigators interested in working with the data should contact the corresponding author.
Standard protocol approvals, registrations, and patient consents
The authors confirm that the study is an observational retrospective minimal-risk study and no consent is required. Our study was approved by the institutional review board at each of the included institutions.
During the study period a total of 2203 procedures were performed through TRA (1697 patients underwent a diagnostic procedure and 506 had an interventional procedure). Mean (SD) age was 56.1 (15.2) years, 1355 (60.8%) were women, and 1189 (53.9 %) underwent the procedure in the outpatient setting. Figure 1 demonstrates the number of TRA cases compared with TFA cases in the included centers over time and figure 2 shows the trend in diagnostic and interventional cases during the study period.
The predefined goal of each procedure was successfully achieved in 2082 (94.5%) cases. The success rate was 95.3% for diagnostic procedures and 91.7% for interventional procedures. Table 1 summarizes the unsuccessful cases through TRA, and figure 3A represents the distribution of successful and failed TRA cases during the study period. Crossover to TFA was required in 114 (5.2%) cases (79 diagnostic procedures and 35 interventional procedures, p=0.044)]. Crossover to TFA occurred in stage I in 44 (38.6%) cases, stage II in 32 (28.1%), stage III in 28 (24.6%), and stage IV in 10 (8.8%) patients. Figure 3B illustrates the trend in cases that required a crossover to TFA over time.
A total of 14 (0.6%) complications occurred during the study period. No major complications were noted. Minor complications included forearm hematoma that improved with local compression (n=11), proximal radial artery dissection (n=1), radial artery pseudoaneurysm (n=1), and forearm skin infection treated with oral antibiotics (n=1). The trend of complications related to TRA is shown in figure 4.
A total of 1697 cerebral angiograms were attempted using the TRA technique, and 1618 (95.3%) achieved the predefined goal of the procedure successfully. TRA access was obtained through the anatomical snuffbox in 484 (28.5%) cases and through the radial artery in the forearm in 1208 (71.2%). Access through the ulnar artery was obtained in five cases (0.3%). A Simmons-2 catheter was used as a first-line insertion catheter in most cases (n=915). Other catheters used first-line included Simmons-1 (n=563), Simmons-3 (n=278), Vertebral catheter (n=35), VTK (n=3), and angled taper (n=3). There was a need to convert to a different catheter in 57 (3.4%) cases to help in reaching the target blood vessel. A 0.038 in pre-shaped wire was used in 1077 (63.5%) cases and a 0.035 in pre-shaped wire was used in 620 (36.5%) cases.
All four major cerebral blood vessels (bilateral vertebral arteries and internal carotid arteries) were imaged in 438 (27.1%) out of the 1618 successful cases. Contrast use was 92.3±52.4 mL, total radiation dose was 216.4±337.4 mGy, and total fluoroscopy time was 13±8.7 min. In some cases, imaging of the right internal carotid artery was achieved by injecting contrast in the right common carotid artery (n=259) and imaging of the left internal carotid artery was achieved by injecting contrast in the left common carotid artery (n=315).
Minor complications (n=9) during diagnostic procedures included forearm hematoma that improved with local compression (n=8) and forearm skin infection treated with oral antibiotics (n=1).
A total of 506 interventional procedures were attempted using the TRA technique and 464 (91.7%) achieved the predefined goal of the procedure. Table 2 summarizes the interventional procedures performed through TRA. The most used guide catheter for flow diversion and mechanical thrombectomy cases was the AXS Infinity (Stryker Neurovascular, Fremont, California, USA) in 86/165 cases followed by Benchmark 071 (Penumbra, Oakland, California, USA) in 42/165 cases and Sofia (Microvention, Aliso Viejo, California, USA) in 20/165 cases. The most used guide catheter for cerebral aneurysm coil embolization cases was the Benchmark 071 (Penumbra) in 49/97 cases followed by Sofia (Microvention) in 28/97 cases and AXS Infinity (Stryker Neurovascular) in 10/97 cases. Contrast use was 143.2±58 mL, total radiation dose was 233.5±658.3 mGy, and total fluoroscopy time was 41.2±31.1 min.
The present study is the largest study of its kind to demonstrate the technical feasibility and safety of the radial approach in the neuroendovascular field. In this study, we found that TRA is safe and feasible as a first-line approach for various neurointerventions. Furthermore, we present the learning curve of six large academic neuroendovascular centers who have been early adopters of the ‘radial-first’ approach.
TRA offers several advantages over TFA. First, superficial access to arterial compression via the radial artery allows better control of hemostasis compared with the femoral artery (without the use of a percutaneous closure device), which may be under several centimeters of tissue. Second, TRA is associated with a significant reduction in vascular complications such as groin and retroperitoneal hematoma.18 Third, the superficial position of the radial artery and the lack of surrounding nervous tissue near the styloid process significantly reduces the likelihood of the formation of traumatic neuromas or arteriovenous fistulas.22 Importantly, the post-procedural ability to ambulate and discomfort is substantially lower with TRA compared with TFA.23 Finally, TRA is associated with significant in-hospital cost reduction when compared with TFA.24
Given these advantages, TRA has been adopted for most cardiac procedures over the past two decades; however, it remains rarely employed for neurointerventional procedures. This is largely related to the comfort level of neurointerventionists with TFA. In our study we found that converting to TRA is feasible and safe. The success rate was approximately 95.3% for diagnostic procedures and 91.7% for interventional cases. Furthermore, none of the 2203 patients included in this study experienced a major access-related complication using TRA. The results of our study match similar findings from the cardiology literature in the early stages of transitioning to TRA for most cardiac procedures.19 25 In the landmark RIVAL (Radial vs femoral access for coronary interventions) trial, patients with acute coronary syndrome were randomly assigned to radial or femoral access.23 The primary outcome was a composite of death, myocardial infarction, stroke, or non-coronary artery bypass graft-related major bleeding at 30 days. A total of 7021 patients were enrolled in 158 hospitals around the world. There was no difference in the primary outcome between the two groups.23 Importantly, there was a significantly lower rate of local vascular complications with TRA than with TFA.23
With regard to the failure rate with TRA in our study, crossover to TFA occurred in approximately 6.9% of interventional and 4.7% of diagnostic angiograms. We classified the challenges associated with TRA into four stages: (I) obtaining access to the radial artery; (II) navigation across the arm; (III) navigation across the arch and main supra-aortic branch selection; (IV) distal support for intracranial interventions. We found that challenges in stage I were the most common cause for crossover to TFA, which can be explained by the new experience with radial arterial puncture. Failure in stages III and IV compose about one-third of the cases that required crossover to TFA, which raises an important limitation related to TRA in neurointervention likely due to the absence of neuroendovascular-specific TRA catheters.
Previous studies have demonstrated a learning curve for TRA requiring appropriate training, particularly during initial attempts.8–10 The technical difficulties associated with TRA are mainly related to catheter manipulation and negotiation of the left vertebral artery and left common carotid artery, which are usually more anatomically straightforward with TFA. In addition, an important factor in the transition process from TFA to TRA is nursing and technologist staff training to become familiar with the new room arrangement, forearm preparation, and potential complications related to the access site. Our results show that, even though the number of procedures has increased with time, the number of complications and crossover to TFA remained similar, which can be explained by the increased experience among operators in the included institutions.
Given the associated learning curve, it was expected that TRA may be associated with a higher radiation dose and increased contrast volume. However, the procedural metrics using TRA were comparable to those reported in the literature using TFA.26 27 A study by Rigattieri et al compared radiation exposure in 4110 patients undergoing coronary procedures, of which 1153 were TRA and the remainder were TFA. The authors found that TRA was not associated with increased radiation exposure compared with TFA.28
An important limitation of TRA is the smaller caliber of the radial artery compared with the femoral artery, which prevents interventionists from using catheters larger than 8 Fr in most patients. In addition, the absence of neuroendovascular-specific TRA devices and catheters poses another contemporary challenge to adopting radial-first as the default approach for all interventions. This is especially important for stroke thrombectomy as it may require large-bore aspiration catheters or balloon-guided catheters. However, our study shows that a wide range of procedures can be performed successfully, including cerebral aneurysm embolization, flow diversion, mechanical thrombectomy, and others. The total success rate for interventional procedures was 91.7%, with only 6.9% of the cases requiring crossover to TFA. These findings confirm previous observations from studies that evaluated the use of TRA in neuroendovascular procedures.3 8 14 18 20 29
Our study is limited by the retrospective design and the lack of a control group. However, the study has key strength points, including the large number of procedures and the multicenter design. Future studies are necessary to confirm our findings and discuss the cost-effectiveness of this approach.
In this early stage of transforming to the radial-first approach for neuroangiography, TRA was safe with a low complication rate for both diagnostic and interventional procedures. A wide range of procedures were completed successfully using TRA.
EA and SAK are joint first authors.
Twitter @PascalJabbourMD, @Starke_neurosurgery, @ashupjadhav, @alex_spiotta
Contributors All authors have: provided a substantial contribution to the conception and design of the studies and/or the acquisition and/or the analysis of the data and/or the interpretation of the data. They have drafted the work or revised it for significant intellectual content and approved the final version of the manuscript. They agree to be accountable for all aspects of the work, including its accuracy and integrity.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement Data are available upon reasonable request. Additional data from this project can be acquired by contacting the corresponding author.