Background The transradial approach for cardiac catheterization is associated with improved patient safety and satisfaction in comparison with the transfemoral approach. Prospective data for the transradial approach for cerebral arteriography are lacking.
Objective To carry out a prospective study of consecutive patients undergoing transradial cerebral arteriography at our institution to evaluate the safety, feasibility, and limitations of this approach.
Methods Consecutive patients referred for diagnostic cerebral arteriography at an institution with minimal transradial experience were enrolled until 50 right transradial diagnostic cerebral arteriograms were obtained. A procedural staging system was developed and goals of angiography were defined before each procedure. The primary outcome was the ability to achieve the predefined goals using the transradial approach. Secondary outcomes included the technical ability to access and inject each supra-aortic artery of interest and the incidence of complications.
Results A total of 65 patients were screened; 15 were excluded owing to contraindications and 50 underwent attempted right transradial cerebral arteriography. The primary outcome was achieved in 44 patients (88%). Failures occurred at stage 1 (n=3, 6%), stage 2 (n=1, 2%), stage 3a (n=1, 2%), and stage 3b (n=1, 2%). Crossover to the transfemoral approach occurred in four patients (8%) and the procedure was terminated in two patients (4%). All supra-aortic arteries of interest were accessed and injected, with success rates between 89% and 100% with the exception of the left vertebral artery (successful in 59%). There were no major complications and five minor complications.
Conclusion Neurointerventionalists attempting the transradial approach can expect to achieve moderate early success and a low complication rate.
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The field of interventional cardiology has adopted a radial-first approach over the traditional transfemoral approach because it is associated with lower bleeding and vascular complications and improved patient safety and satisfaction.1 2 These benefits have generated interest in adopting the transradial approach for neuroendovascular procedures as well3 and retrospective series have reported favorable preliminary results.4–9
Transitioning to an alternative surgical approach may be challenging or perceived as unnecessary for practitioners who have mastered and trust the transfemoral approach. Prospective data for the safety and efficacy of the transradial approach for cerebrovascular procedures are lacking and the technical capabilities and limitations need to be defined before a randomized comparison with the transfemoral approach can be conducted.
The aim of this trial was to prospectively study consecutive patients undergoing transradial cerebral arteriography at our institution to evaluate the safety, feasibility, and limitations of this approach.
This study was a prospective, single-arm, single-center registry of 50 consecutive eligible patients who underwent right transradial diagnostic cerebral arteriography at a large academic medical center in the United States. The study protocol was approved as a quality improvement project by the institutional quality improvement review committee. The study was designed and conducted by the academic investigators. Funding was provided by MicroVention Inc, (Aliso Viejo, California, USA) and The Pittsburgh Foundation (Pittsburgh, Pennsylvania, USA); funding was used for purchasing equipment necessary for transradial angiography. Sponsors were not involved in acquisition, analysis, or interpretation of the data.
All inpatients and outpatients aged ≥18 years were eligible for inclusion in the study if they were referred for diagnostic cerebral arteriography. The diagnostic goal(s) of the procedure were explicitly defined (table 1) before the procedure. Patients were excluded if they had no palpable right radial artery pulse, a history of a right transradial arterial line or arteriography within the past 30 days, recent right upper extremity or high thoracic trauma, presence of an ipsilateral arteriovenous fistula for hemodialysis, right upper extremity lymphedema, Raynaud’s disease, a history of right radial artery harvest, or prior left upper extremity disability or amputation. The study was concluded after 50 patients had undergone attempted transradial diagnostic cerebral angiography.
Four neurointerventional operators performed the procedures. Each operator had experience of performing more than 100 transfemoral diagnostic cerebral arteriography scans and between 5 and 15 cases of right transradial diagnostic cerebral arteriography before the study.
Transradial arteriography was performed with a standardized procedural workflow. Eutectic mixture of local anesthetics (2.5% lidocaine, 2.5% prilocaine) cream (2.5 g) and an occlusive Tegaderm bandage was applied to the right radial access site 30 min before puncture. Clinical testing of collateral hand circulation was not performed. A blood pressure cuff was placed on the left arm or either leg. Intravenous lines were placed in the left arm or either leg, and a pulse oximeter was placed on the left hand. Bilateral groin sites were shaved, prepped, and draped. The right wrist was positioned in gentle extension, secured to an articulating arm board, and prepped and draped. Intravenous conscious sedation or general endotracheal anesthesia was administered. Lidocaine (1%, 1.0 mL) was injected into the subcutaneous space over the right radial access site, taking care to avoid inadvertent puncture of the radial artery.
Ultrasound guidance was used to perform single-wall puncture of the radial artery with a 21-gauge micropuncture needle. A 0.018" microwire was advanced, followed by a hydrophilic 10 cm 5 F Glidesheath Slender sheath (Terumo, Somerset, New Jersey, USA). The sheath was flushed with heparinized saline and connected to a continuous infusion of heparinized saline (3000 U per 1 litre bag). A cocktail of 2.5 mg verapamil and 200 μg nitroglycerin was diluted in 15 mL blood and administered via the sheath side port to the radial artery. Unfractionated heparin (3000 U) was administered intravenously, except in patients with known intracranial hemorrhage.
Retrograde radial arteriography was performed through the sheath side port, and a diagnostic catheter was advanced in tandem with an 0.035" 3 mm J-wire or 0.035" guidewire. Fluoroscopy was initiated over the chest (to keep radiation as low as reasonably achievable) unless any resistance was encountered. If resistance was met, fluoroscopy was performed over the arm to guide access to the aortic arch.
Diagnostic cerebral arteriography was performed using a variety of diagnostic catheters including 100 cm hydrophilic-coated 4 F and 5 F Simmons 1, Simmons 2, and Simmons 3 catheters, and 4 F and 5 F Vert catheters. The ability to access and inject each supra-aortic artery of interest was recorded. With an 0.035" exchange-length wire left in the aortic arch, the diagnostic catheter was removed and a 5 F Pigtail catheter was advanced to the aortic arch and arch aortography was performed.
At the conclusion of the procedure an inflatable transradial tourniquet was applied, the sheath was removed, and the band was inflated to achieve patent hemostasis. The hemostatic band was deflated in accordance with institutional protocol over 1 hour. The presence or absence of a right radial artery palpable pulse was evaluated by the investigators and recorded before discharge for outpatients or within the first 24 hours after the procedure for inpatients. From 2 weeks after their procedure, patients were contacted by the investigators for telephone follow-up to identify any delayed complications.
The primary outcome was the ability to achieve the predefined goals of diagnostic cerebral arteriography (table 1) using the transradial approach. A procedural staging system was developed to further subclassify the procedure into formalized stages:
Stage 1 – the right radial artery is punctured and a sheath is inserted into the artery.
Stage 2 – a diagnostic catheter is advanced to the aortic arch.
Stage 3a – the goals of arteriography are achieved with standard techniques—namely, the use of 4 F or 5 F catheters, 0.035" or 0.038" guidewires, and exchange-length J-wires.
Stage 3b – the goals of arteriography are achieved with adjunctive techniques—namely, any additional catheters or wires such as long sheaths, intermediate catheters, microcatheters, and microwires,
Crossover to the transfemoral approach meant the decision was made to convert the access site from the radial artery to the femoral artery. Termination of the procedure meant a decision for termination was made because the risk or cost of proceeding with further arteriography outweighed the potential benefits of proceeding. Either crossover or termination could occur if the goals of arteriography could not be achieved using the transradial approach.
Secondary outcomes included the technical ability to access and inject the supra-aortic arteries using the transradial approach. Supra-aortic arteries were deliberately selected for catheterization based on the predefined goals of each procedure, and injection of arteries that would not directly fulfill the goals of the procedure was avoided. ‘Accessed and injected’ meant the catheter was positioned securely within the artery of interest and arteriography was performed. ‘Attempted but unable’ meant the catheter could not be positioned securely within the artery of interest.
Other secondary outcomes were designed to evaluate the safety of the transradial approach. Major complications were defined as asymptomatic radial artery occlusion, critical hand ischemia, compartment syndrome, arteriovenous fistula development, radial artery pseudoaneurysm, radial artery avulsion or eversion, radial nerve injury, stroke, intracranial hemorrhage, or death. Minor complications were defined as radial artery vasospasm, local forearm ecchymosis, and local forearm hematoma. Procedure-related complications were recorded by the operator immediately at the conclusion of the procedure or during postprocedure evaluation of the radial artery pulse. Investigators recorded delayed complications after 2 weeks during a telephone follow-up with patients.
Univariate analysis using X2 or paired t-test was performed to identify any association between primary and safety endpoints and patient characteristics or procedural details. Variables with a p value ≤0.4 were included in multivariate logistic regression analysis. SPSS software version 23.0 (IBM, Armonk, New York, USA) was used.
Beginning in September 2018 and for 27 days, 65 consecutive patients referred for diagnostic cerebral arteriography without the possibility of intervention were screened for inclusion in the trial. Fifteen patients (23%) were excluded: six had a history of a right transradial arterial line or arteriography within the past 30 days, three had no palpable right radial artery pulse, three had recent right upper extremity or high thoracic trauma, one had right upper extremity lymphedema, one was a wheelchair-bound patient who would not be able to adhere to postoperative avoidance of high-resistance wrist movements with transfers, and one was a patient with a symptomatic, giant right superior cerebellar artery aneurysm for whom the investigators wanted to preserve the right transradial route for expected future endovascular intervention. The remaining 50 patients constituted the transradial study cohort and their baseline characteristics are shown in table 2.
For the four primary operators, the number of cases performed was 27, 10, 9, and4, respectively. In four cases (8%) the first diagnostic catheter was exchanged for a second one to complete the procedure; no case required more than two diagnostic catheters.
Predefined goals of diagnostic cerebral arteriography were achieved using the transradial approach in 44 patients (88%) (figure 1). Stage 1 failure occurred in three patients (6%); following puncture of the radial artery with a micropuncture needle, the 0.018" microwire could not be successfully advanced into the artery despite multiple attempts and crossover occurred. Stage 2 failure occurred in one patient (2%); a 360-degree radioulnar loop was encountered, the diagnostic catheter could not be advanced to the aortic arch and crossover occurred.
Two patients (4%) terminated the procedure during stage 3. In one case, the patient experienced radiographically confirmed radial artery spasm, resulting in termination of the procedure (stage 3a failure). In one other patient with intraparenchymal hemorrhage, where predefined goals of arteriography required selective internal carotid artery injection, only the common carotid artery could be accessed despite adjunctive catheter and wire techniques (stage 3b failure).
Technical capabilities and limitations
Injection success rates for all supra-aortic arteries were between 89% and 100%, with the exception of the left vertebral artery (59%). Specific results for each artery are listed in table 3.
No major complications occurred in this study. Forty-four patients were directly examined by investigators following the procedure and all of them had a palpable right radial artery pulse. However, the presence or absence of a postprocedural right radial artery pulse was not recorded for six patients, although this was required by the trial protocol. Five minor complications occurred: three patients (6% of total) had intraprocedural radial artery vasospasm (two of whom responded favorably to additional intravenous conscious sedation and intra-arterial vasodilators) and two patients developed local hematomas at the puncture site, which completely resolved with manual pressure.
Factors associated with success, failure, and complications
The ability to achieve the goals of diagnostic cerebral arteriography using the transradial approach was not significantly associated with any patient characteristic or procedural detail on univariate and multivariate statistical analyses. Intraprocedural radial artery vasospasm was noted more commonly with the use of 4 F versus 5 F catheters (incidence 25% vs 3.7%, p=0.12) and occurred in younger patients (43±17 years vs 56±14 years, p=0.15) on univariate analysis. These non-significant associations showed a trend towards, but did not reach, significance on multivariate logistic regression analysis (smaller catheter size, p=0.16; younger age, p=0.13). The development of local hematoma at the puncture site was not statistically associated with any patient characteristic or procedural detail, although it was noted that both patients who developed local hematoma were receiving active dual antiplatelet therapy.
Although several retrospective case series have demonstrated the feasibility and safety of the transradial approach for diagnostic cerebral arteriography,4–9 its adoption by neurointerventionalists has been relatively gradual. These retrospective studies are influenced by selection bias, which limits the external validity, and thus it is difficult to know how generalizable the experience of select centers or experts may be to other operators who have only limited or no experience with the transradial approach. For neurointerventionalists considering the right transradial approach, a prospective analysis of consecutive patients and knowledge of operator experience is warranted.
This study is the first prospective study of the transradial approach for diagnostic cerebral arteriography. In the study we report our own initial experience with the right transradial approach with operators who had only limited prior experience with performing transradial angiography. The study’s results represent the earliest point of the experience–performance curve and provide neurointerventionalists with realistic expectations about the efficacy and safety outcomes they might achieve with the transradial approach, either as a first-line approach for diagnostic cerebral arteriography, or when crossover to the right transradial approach occurs.
The study introduces and uses an intuitive staging system (stages 1 to 3b), which divides each procedure into distinct segments. This staging system helps to focus attention on exactly where and when challenges occur during transradial arteriography and these stages may be used also to organize strategies to overcome challenges.
The experience–performance curve for transradial cerebrovascular procedures needs to be defined and, when it has reached a plateau, a head-to-head comparison of transfemoral and transradial approaches will help to determine the first-line strategy for neurovascular patients. In this report, the rate of stage 1 failure was 6%. Performing ultrasound-guided radial artery cannulation is challenging because of the radial artery’s small size (average diameter in our study 2.1±0.7 mm) and also because with each failed cannulation attempt, local vasospasm and hematoma formation further obscures the pulse. The rate of radial artery cannulation failure reported among interventional cardiologists decreases with experience from ~10% in beginners to ~1% in high-volume transradial operators10 11; we expect that the 6% stage 1 failure rate reported here will decrease with increased transradial experience.
Vascular anatomical variations of the upper extremity, such as significant radial artery tortuosity, stenosis, hypoplasia, radioulnar looping, or abnormal origin of the radial artery are common and potentially manageable abnormalities.12 In this study we report an 11% rate of radial artery anomaly but only a 2% (1 in 50) stage 2 failure rate, due to a radioulnar loop that was immediately recognized but could not be crossed safety with a diagnostic catheter. Other abnormalities, such as the rare instance of a retroesophageal right subclavian artery (0.45% incidence12), may necessitate crossover, but were not noted in this study. Operators attempting the transradial approach should refamiliarize themselves with normal and variant upper extremity vasculature in order to recognize and manage any anomaly safely and effectively.
Navigating the aortic arch from the right transradial approach requires a distinct, but related, set of skills to those needed when navigating the same arch from the transfemoral approach because the inlet to the arch is the ostium of the brachiocephalic trunk instead of the descending thoracic aorta. In traditional transfemoral angiography, reformatted catheters are often positioned in the ascending aorta when they are steered. Because of the right-to-left orientation of the right transradial approach, reformatted catheters may also be positioned in the descending thoracic aorta, which carries a new set of advantages and challenges.
Diagnostic catheters specifically designed for transradial cerebral arteriography are not yet commercially available, and a variety of different catheters were used in this trial. The Simmons 1 shape is often the simplest to reformat in the aortic arch, but Simmons shapes 2 and 3, which have longer tails, can be useful to catheterize the left vertebral artery when the left subclavian artery is elongated. We noticed that 4 F catheters tended to ripple or buckle during catheter manipulation and we hypothesized that the association between the use of 4 F catheters and intraprocedural radial artery vasospasm might be related to irritation of the vessel by this deformation of the catheter. The rate of 4 F catheter-induced vasospasm was higher than for the 5 F catheters (25% vs 3.7%), though this did not achieve statistical significance with a study size of 50 patients (p=0.12).
The right transradial approach has technical limitations. We were only able to successfully access and inject the left vertebral artery 59% of the time (consistent with prior reports of 52–59%5 6) and one strategy to overcome this limitation is to firmly inject the left subclavian artery, which we were able to access and inject 94% of the time. Similarly, when the right common carotid artery arising from the right subclavian artery is at a very acute angle, the dramatic change in direction poses a technical challenge. This situation is further exacerbated when the right common carotid artery ostium is close to the aortic arch because as the ostium gets closer to the arch there is less resistance to catheter herniation into the arch. Technical success rates for transradial procedures have been reproducibly shown to improve with operator experience1 and we expect that our stage 3 failure rate of 4% will decrease with experience.
The most significant limitation of this study is the small sample size, which will be increased in future studies. Several small violations in study protocol occurred; six outpatients in this study were discharged before the investigator examined their right radial artery pulse, though none of these patients identified delayed complications during their follow-up telephone conversation. For consistency this study focused solely on the right transradial approach but did not evaluate alternative wrist approaches, such as the left transradial, anatomical snuffbox, or transulnar approaches. Patient satisfaction and further details of anatomical and technical challenges will be the focus of future inquiry.
Despite limited experience with the transradial approach for diagnostic cerebral angiography, predefined goals of angiography were achieved 88% of the time. Neurointerventionalists making a transition to the transradial approach can expect to achieve moderate early success and a low complication rate.
Contributors Study conception: BMZ, BTJ. Data acquisition: BMZ, DAT, JS, MB. Data analysis: BMZ, DAT, BAG, TGJ, AJ. Critical revision of manuscript: all authors. Final approval of manuscript: all authors.
Funding This work was supported by The Pittsburgh Foundation grant number UN2018-ARMPITT and by Microvention, Inc grant titled “Arterial Radial Management at UPMC.”
Competing interests BTJ: consultant: Medtronic. TGJ: consultant: Stryker Neurovascular; ownership interest: Anaconda; advisory board/investor; FreeOx Biotech, Route92, Blockade Medical; consultant; honoraria: Cerenovus. BAG: consultant: Microvention.
Provenance and peer review Not commissioned; externally peer reviewed.
Patient consent for publication Not required.