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The Neuroradiology Journal logoLink to The Neuroradiology Journal
. 2022 Dec 23;36(4):442–452. doi: 10.1177/19714009221147230

Therapeutic efficacy and complications of radial versus femoral access in endovascular treatment of unruptured intracranial aneurysms

Michiyasu Fuga 1,✉, Toshihide Tanaka 1, Rintaro Tachi 1, Kyoichi Tomoto 1, Shun Okawa 1, Akihiko Teshigawara 1, Toshihiro Ishibashi 2, Yuzuru Hasegawa 1, Yuichi Murayama 2
PMCID: PMC10588597  PMID: 36564905

Abstract

Purpose

The transradial approach (TRA) in neuroendovascular treatment is known to have a lower risk of complications than the transfemoral approach (TFA). However, little research has focused on assessments of efficacy and risk of complications in the treatment of intracranial aneurysms. This study aimed to compare the efficacy and complications of TRA and TFA in coil embolization of unruptured intracranial aneurysms (UIAs) at our institution.

Methods

Consecutive patients who underwent endovascular surgery via TRA or TFA at a single institution from 1 April 2019, to 28 February 2022, were retrospectively analyzed. Patients were classified into TRA and TFA groups and assessed using propensity-adjusted analysis for outcomes including fluoroscopy time, volume embolization ratio (VER), and complications.

Results

A total of 163 consecutive UIAs were treated with coil embolization during the 35-months study period. The incidence of minor access site complications (ASCs) was significantly higher with TFA (20%, 25/126) than with TRA (2.7%, 1/37; p = 0.01). Propensity-adjusted analysis (matched for age, sex, aneurysm volume, embolization technique, and sheath size) revealed that TRA was associated with a lower risk of minor ASCs (odds ratio, 0.085; 95% confidence interval 0.0094–0.78; p = 0.029). However, TRA did not differ significantly from TFA with respect to fluoroscopy time, VER, major ASCs, and non-ASCs.

Conclusions

Coil embolization for UIAs via TRA can reduce risk of minor ASCs without increasing the risk of non-ASCs compared with conventional TFA, and can achieve comparable results in term of efficacy and fluoroscopy time.

Keywords: Access site, fluoroscopy time, neurointervention, transfemoral approach, transradial access, transradial approach, volume embolization ratio

Introduction

In recent years, more and more reports in the field of cerebral endovascular treatment have described treatments via the transradial approach (TRA). Early experience at various institutions has already demonstrated that TRA is superior to the transfemoral approach (TFA) because of technical ease of the procedure in obese patients, reduction of burdens on the patient and medical care costs associated with early discharge, and lower risk of puncture site complications.1–10

On the other hand, compared with TFA, TRA has been shown to have the following drawbacks: increased radiation exposure due to prolonged operation time; 8 difficulty performing the procedure for anatomic reasons; 4 a lack of TRA-specific devices; and the need for proficiency in the procedure.2,11–14 However, the majority of the literature comparing TRA and TFA is based on reports of diagnostic cerebral angiography,15–21 carotid stenting,22-24 vertebral and basilar artery stenting, 25 mechanical thrombectomy,26–29 and flow diversion,30,31 with few studies on intracranial aneurysms.

As for comparative analyses of TRA and TFA, most studies have paid attention to diagnostic rather than interventional procedures.5,8 Hence, few researchers have focused on the treatment of intracranial aneurysms to assess efficacy and risk of complications.

In the present study, efficacy and complication rate in coil embolization for unruptured intracranial aneurysms (UIAs) at a single center were compared between TRA and TFA using propensity-adjusted analysis. With the accumulation of experience, the clinical benefits and disadvantages of TRA will become apparent.

Methods

Study design

Consecutive patients who underwent coil embolization for UIAs using TFA or TRA at Jikei University Kashiwa Hospital between 1 April 2019 and 28 February 2022, when the authors (M.F. and R.T.) were assigned to and started endovascular treatment at that institution, were retrospectively reviewed from maintained data. The present cohort study was conducted in accordance with Strengthening the Reporting of Observational Studies in Epidemiology guidelines for cohort studies. Our institutional review board approved this study, and because of the retrospective design, the need for obtaining consent from patients was waived.

Patient eligibility and entry procedure

Data from our institution’s database of collected patient information were extracted and analyzed for age, sex, aneurysm location, aneurysm characteristics, embolization technique, sheath size, embolization result (modified Raymond-Roy classification (MRRC)), volume embolization ratio (VER), fluoroscopy time, total contrast, hospitalization duration, and complications.

Endovascular procedure

All patients treated in this study underwent diagnostic cerebral angiography in a different setting prior to aneurysm embolization, via transbrachial approach for patients planned for treatment via TRA and via TFA for patients planned for treatment via TFA in order to pre-assess the access route and aneurysm. All diagnostic cerebral angiography was successfully completed without changing access site. In our institution, treatment with TFA as a first choice was performed until February 2021, while TRA has been the first choice since March 2021. TRA procedures were performed only by two surgeons (M.F. and R.T.) in a uniform manner.

TRA technique

All patients were preoperatively evaluated for palmar collateral circulation with the Allen test. The radial artery diameter was measured by brachial angiography at the time of diagnostic cerebral angiography. Based on the success of preoperative diagnostic cerebral angiography, coil embolization for UIAs via TRA was attempted in all patients with a radial artery diameter of 2.0 mm or greater.4,32–34

TRA was performed in all patients using a uniform procedure as follows.

The radial artery was punctured with a 22-G BD Insight-A Peripheral Arterial Catheter (Becton Dickinson, Franklin Lakes, NJ, USA) using an anterior or counter-puncture technique to secure the true lumen of the vessel. The Radial Artery Access With Ultrasound Trial (RAUST) demonstrated that ultrasound assistance facilitated prompt and efficient cannulation in the beginning, but ultrasound guidance was only employed at our institution for difficult punctures. 35 The Micropuncture Kit (Cook Medical, Bloomington, IN, USA) and 4-Fr short sheath (Terumo, Somerset, NJ, USA) were gradually replaced with larger ones in that order via guidewire. Radial angiography was then performed through the 4-Fr short sheath, and if vasospasm occurred in the radial artery, 1 mg of isosorbide dinitrate was infused over 1 min. Subsequently, a 100-cm 4-Fr JB1 catheter (Medikit, Tokyo, Japan) was guided to the ascending aorta with a 180-cm soft-tipped 035-inch hydrophilic wire (Terumo). The guidewire was pulled out, an Amplatz Super Stiff guidewire (Boston Scientific, Natick, MA, USA) was inserted into the catheter, with then the wire left in place, the JB1 catheter was pulled out, and the 4-Fr short sheath was exchanged for a 6-Fr straight-shaped guiding sheath (FUBUKI Dilator Kit (OD, 2.7 mm; ID, 0.090 inch; length, 90 cm); Asahi Intecc, Aichi, Japan). The guiding sheath was then inserted into the target vessel in a telescopic fashion using a 130-cm 5-Fr Simmons-shaped catheter (Medikit) for the anterior circulation or a 130-cm 5-Fr Non-taper Angle catheter (Terumo) for the posterior circulation. After this, the procedure was the same as the procedure for TFA.

Access site crossover

Access site crossover was defined as when one treatment approach (TRA or TFA) was attempted but could not be completed and the access site was changed to the other approach for completion of treatment. The outcomes of patients with access site crossover were assigned to the approach that ultimately allowed completion of treatment.

Management

Coil embolization was carried out in patients under general anesthesia. Intraoperatively, heparin was administered intravenously to maintain the activated clotting time above twice the normal value. For both TRA and TFA, patients were premedicated with dual-antiplatelet agents (aspirin at 100 mg/day, clopidogrel at 75 mg/day) for at least 14 days prior to the procedure. Postoperatively, a single antiplatelet agent (aspirin alone) was continued for 4 weeks if no stent was used. If a stent was deployed, dual-antiplatelet agents (aspirin at 100 mg/day, clopidogrel at 75 mg/day) were administered for 6 months. The hemostatic devices used were the TR Band (Terumo) for TRA and Angio-Seal VIP (Terumo) for TFA.

Angiographic evaluation

Aneurysm characteristics (aneurysm size, neck width, aneurysm volume) and VER were estimated with NeuroVision software (Cybernet Systems, Tokyo, Japan). 36 The dome-to-neck ratio was computed as the ratio of dome width to neck width. VER is based on the following formula: VER = (volume of embolization coils)/(volume of aneurysm) × 100. All embolization results immediately after treatment were evaluated using MRRC, as follows: Class I, complete obliteration; Class II, residual neck; Class IIIa, residual aneurysm showing contrast within coil interstices; and Class IIIb, residual aneurysm showing contrast along the aneurysm wall. 37 MRRC was graded by two interventional neurosurgeons (M.F. and R.T.). In cases where the reviewers disagreed, the third interventional neurosurgeon (A.T.) participated in a review and a consensus decision was obtained.

Complication assessment

Complications were evaluated separately for those related and unrelated to the access site. Furthermore, access site complications (ASCs) were categorized as minor (hemorrhages at the puncture site requiring only recompression and asymptomatic occlusion or dissection of the vessel) or major (vascular perforation, compartment syndrome, and retroperitoneal hemorrhages required further intervention, such as blood transfusion or surgical reconstruction). Non-ASCs consisted of cerebral thromboembolic and hemorrhagic complications. Thromboembolic complications included transient ischemic attack, partial occlusion of the central retinal artery, and cerebral infarction. Hemorrhagic complications were identified as all bleeding cerebrovascular events, including intraoperative aneurysm rupture and vascular perforation. Postoperative complications were assessed 24 h after coil embolization, at discharge, and on postoperative day 30. Radial artery occlusion was defined as the lack of a palpable radial artery and a negative reverse Allen test.

Statistical analysis

All statistical analyses were performed using EZR software (Saitama Medical Center, Jichi Medical University, Saitama, Japan), which is based on R and R Commander. 38 For comparisons between TRA and TFA, categorical variables are presented as frequencies and percentages, and were analyzed using χ2 analyses or Fisher’s exact test, as appropriate. Continuous variables, on the other hand, are shown as mean and standard deviation, and were evaluated using Student’s t test. Furthermore, propensity-adjusted analysis (matching for age, sex, aneurysm volume, embolization technique, and sheath size) was conducted to analyze the risk of minor ASCs with binary logistic regression analysis, and efficacy assessed as fluoroscopy time and VER with linear regression analysis. Values of p < 0.05 were defined as statistically significant.

Results

Patient background

A total of 154 patients with 163 consecutive UIAs underwent coil embolization and were followed-up during a 35-months research period at a single center. Of the 163 procedures, 50 were initially planned to be treated by TRA (Figure 1). Of these, five aneurysms were embolized by TFA, because of radial artery diameters less than 2.0 mm (Figure 1). Another eight aneurysms were attempted by TRA initially, but the treatment was completed by TFA because the catheter was difficult to deliver due to a steep angle at the origin of the common carotid artery (CCA) (2 right, six left) (Figure 1). Ultimately, 37 patients (23%) were completed by TRA and 126 patients (77%) were completed by TFA (Figure 1). The rate of access site crossover from TRA to TFA was 18% [8/45] and from TFA to TRA was 0% [0/118].

Figure 1.

Figure 1.

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Patient selection algorithm. A total of 163 consecutive unruptured intracranial aneurysms were treated with coil embolization. Fifty of the 163 aneurysms were initially planned to be treated with TRA. Of these, five were embolized with TFA because the diameter of the radial artery was less than 2.0 mm. Eight of the aneurysms in which TRA was attempted were converted to TFA because the origin of the common carotid artery was at a steep angle, making navigation of the guiding sheath difficult. Finally, coil embolization was completed with TRA in 37 patients (23%) and with TFA in 126 patients (77%).

No significant difference was seen between patients in the TRA group and in the TFA group with regard to mean age, sex, aneurysm location, aneurysm size, dome-to-neck ratio, and aneurysm volume (Table 1). Neck width was significantly smaller in the TRA group (4.2 ± 1.5 mm) than in the TFA group (5.3 ± 2.8 mm; p = 0.041) (Table 1).

Table 1.

Baseline clinical and aneurysm characteristics of total population and after 1:1 matching in coiled aneurysms.

Total population After 1:1 matching†
Characteristic TRA (n = 37) TFA (n = 126) p value TRA (n = 29) TFA (n = 29) p value
Age (years), mean (SD) 68 (11) 67 (12) 0.65 68 (12) 69 (12) 0.73
Sex, female 23 (62) 80 (64) 1 19 (66) 19 (66) 1
Aneurysm location — N/A — 0.27
ICA aneurysms
 PCoA 10 (27) 23 (18) — 7 (24) 7 (24) —
 AChA 2 (5.4) 5 (4.0) — 2 (6.9) 1 (3.4) —
 Paraclinoid 5 (14) 29 (23) — 5 (17) 6 (21) —
ACA aneurysms
 ACA A1 1 (2.7) 0 (0) — 1 (3.4) 0 (0) —
 ACoA 4 (11) 29 (23) — 2 (6.9) 4 (14) —
 Distal ACA 0 (0) 8 (6.3) — 0 (0) 5 (17) —
MCA aneurysms
 MCA M1 2 (5.4) 2 (1.6) — 2 (6.9) 0 (0) —
 MCA bifurcation 8 (22) 18 (14) — 7 (24) 4 (14) —
BA aneurysms
 Bifurcation 2 (5.4) 6 (4.8) — 2 (6.9) 2 (6.9) —
 SCA 1 (2.7) 2 (1.6) — 0 (0) 0 (0) —
VA aneurysms
 PICA 0 (0) 4 (3.2) — 0 (0) 0 (0) —
 VA 2 (5.4) 0 (0) — 1 (3.4) 0 (0) —
Aneurysm characteristics
 Aneurysm size (mm), mean (SD) 5.1 (2.1) 6.1 (3.0) 0.075 5.2 (2.1) 4.7 (1.6) 0.26
 Neck width (mm), mean (SD) 4.2 (1.5) 5.3 (2.8) 0.041* 4.3 (1.4) 4.3 (1.6) 0.97
 Dome-to-neck ratio, mean (SD) 1.0 (0.25 1.0 (0.26) 0.9 1.0 (0.25) 0.97 (0.18) 0.28
 Aneurysm volume (mm3), mean (SD) 60 (98) 142 (341) 0.19 63 (101) 48 (52) 0.47
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MCA, middle cerebral artery; N/A, not available; PCoA, posterior communicating artery; PICA, posterior inferior cerebellar artery; SCA, superior cerebellar artery; TFA, transfemoral approach; TRA, transradial approach; VA, vertebral artery. * p < 0.05. Data represent number and percentage of patients unless otherwise indicated.

†Propensity adjustment included age, sex, aneurysm volume, embolization technique, and sheath size.

Therapeutic modality and clinical outcome

No significant differences were seen between groups in initial coiling rate, retreatment rate and embolization technique (including primary coiling, balloon-assisted, double-catheter, and stent-assisted methods) (Table 2). Sheaths with larger sizes were used in TFA compared with TRA (p < 0.001) (Table 2). Therapeutic efficacy as determined from angiographic findings was also compared between TRA and TFA groups. MRRC was Class I in 43% of the TRA group (16/37) and 41% of the TFA group (51/126); Class II in 41% of the TRA group (15/37) and 44% of the TFA group (56/126); Class IIIa in 5.4% of the TRA group (2/37) and 5.6% of the TFA group (7/126); and Class IIIb in 11% of the TRA group (4/37) and 9.5% of the TFA group (12/126), respectively (p = 0.97), showing no significant differences between groups (Table 2). On the other hand, VER was 32 ± 7.2% of the TRA group and 29 ± 8.1% of the TFA group (p = 0.025), showing a significant difference (Table 2).

Table 2.

Comparison of procedures, embolization results, and complications of total population and after 1:1 matching in coiled aneurysms

Total population After 1:1 matching†
Characteristic TRA (n = 37) TFA (n = 126) p value TRA (n = 29) TFA (n = 29) p value
Cerebral aneurysm embolization
 Initial 32 (87) 113 (90) 0.56 29 (100) 29 (100) 1
 Retreatment 5 (14) 13 (10) — 0 (0) 0 (0) —
 Embolization technique — 0.063 — 1
  Primary coiling 9 (24) 26 (21) — 7 (24) 8 (28) —
  Balloon-assisted 7 (19) 19 (15) — 6 (21) 6 (21) —
  Double-catheter 0 (0) 18 (14) — 0 (0) 0 (0) —
  Stent-assisted 21 (57) 63 (50) — 16 (55) 15 (52) —
   Neuroform Atlas 21 (57) 57 (45) 0.5 16 (55) 15 (52) 1
   LVIS 0 (0) 5 (4.0) — 0 (0) 0 (0) —
   LVIS Jr. 0 (0) 1 (0.8) — 0 (0) 0 (0) —
Sheath size — <0.001* — 1
 5 Fr 0 (0) 7 (5.6) — 0 (0) 0 (0) —
 6 Fr 37 (100) 38 (30) — 29 (100) 28 (97) —
 7 Fr 0 (0) 4 (3.2) — 0 (0) 1 (3.4) —
 8 Fr 0 (0) 1 (0.8) — 0 (0) 0 (0) —
 9 Fr 0 (0) 76 (60) — 0 (0) 0 (0) —
Embolization result (MRRC) — 0.97 — 0.57
 Class I 16 (43) 51 (41) — 14 (48) 10 (35) —
 Class II 15 (41) 56 (44) — 12 (41) 16 (55) —
 Class IIIa 2 (5.4) 7 (5.6) — 1 (3.4) 0 (0) —
 Class IIIb 4 (11) 12 (9.5) — 2 (6.9) 3 (10) —
VER (%), mean (SD) 32 (7.2) 29 (8.1) 0.025* 33 (7.4) 33 (10) 0.99
Fluoroscopy time (min), mean (SD) 107 (35) 153 (70) <0.001* 103 (31) 116 (44) 0.19
Total contrast (mL), mean (SD) 152 (38) 190 (65) 0.001* 152 (43) 165 (48) 0.29
Hospitalization duration (days), mean (SD) 6.2 (5.9) 7.8 (9.2) 0.3 6.1 (6.2) 5.2 (0.76) 0.44
Complications
 Access site-related 2 (5.4) 26 (21) 0.045* 2 (6.9) 8 (28) 0.079
  minor 1 (2.7) 25 (20) 0.01* 1 (3.4) 8 (28) 0.025*
  major 1 (2.7) 1 (0.8) 0.4 1 (3.4) 0 (0) 1
Non-access site-related 2 (5.4) 10 (7.9) 1 0 (0) 2 (6.9) 0.49
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MRRC, modified Raymond-Roy classification; TFA, transfemoral approach; TRA, transradial approach; VER, volume embolization ratio. *p < 0.05. Data represent number and percentage of patients unless otherwise indicated.

†Propensity adjustment included age, sex, aneurysm volume, embolization technique, and sheath size.

In addition, significant differences were observed between TRA and TFA groups in fluoroscopy time (TRA: 107 ± 35 min vs TFA: 153 ± 70 min; p < 0.001) and total contrast (TRA: 152 ± 38 mL vs TFA: 190 ± 65 mL; p = 0.001) (Table 2). No significant difference in duration of hospitalization was seen between the TRA group (6.2 ± 5.9 days) and TFA group (7.8 ± 9.2 days; p = 0.3) (Table 2).

Complications

Of the 28 ASCs, 26 (93%) were minor complications. In the TFA group, 25 (20%) developed ASCs, including 24 groin hematomas with need for recompression and one asymptomatic common iliac artery dissection. On the other hand, the TRA group showed 1 (2.7%) asymptomatic radial artery occlusion. The incidence of minor ASCs was significantly higher in the TFA group than in the TRA group (p = 0.01) (Table 2). Two of the 28 ASCs (7.1%) were major; one compartment syndrome associated with radial artery perforation in the TRA group and one retroperitoneal bleeding in the TFA group. Regarding TFA, retroperitoneal bleeding resulted in anemia and hypotension, requiring blood transfusion. On the other hand, in TRA, compartment syndrome developed in the right forearm due to perforation of the proximal right radial artery during removal of the guiding catheter. Relief incision was performed to decompress the forearm, and the torn vessel was successfully reconstructed without permanent sequelae. There was no significant difference in the incidence of major ASCs (p = 0.4) (Table 2). Non-ASCs occurred in 2 (5.4%) patients in the TRA group, including one transient ischemic attack and one cerebral infarction. Meanwhile, non-ASCs were observed in 10 (7.9%) patients in the TFA group, consisting of four cerebral infarctions, two transient ischemic attacks, two intraprocedural ruptures, one parent artery perforation, and one partial occlusion of the central retinal artery. No significant difference was identified between groups (Table 2).

Propensity-adjusted analyses

Propensity-adjusted analyses matched for age, sex, aneurysm volume, embolization technique, and sheath size revealed that TRA was associated with a lower risk of minor ASCs (odds ratio, 0.085; 95% confidence interval 0.0094–0.78; p = 0.029) (Table 3). However, TRA did not differ significantly from TFA with respect to fluoroscopy time (14.1-min reduction; 95% CI, −35.8 to 7.6; p = 0.2) or VER (2.4% reduction; 95% CI, −7.5 to 2.6; p = 0.34) (Table 3).

Table 3.

Propensity-Adjusted† predictors of outcomes in radial vs femoral access.

Outcome Measurement (95% CI) p value
Minor complications related to access site (odds ratio) 0.085 (0.0094–0.78) 0.029*
Difference in fluoroscopy time (min) −14.1 (−35.8 to 7.6) 0.2
Difference in VER (%) −2.4 (−7.5 to 2.6) 0.34
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VER, volume embolization ratio.

*p < 0.05.

†Propensity adjustment included age, sex, aneurysm volume, embolization technique, and sheath size.

Illustrative case of access site crossover from TRA to TFA

A 78-year-old woman with left posterior communicating artery aneurysm had difficulty navigating the guiding sheath into the left internal carotid artery cervical segment. Three-dimensional computed tomography angiography showed an acute angle between the innominate artery and the left common carotid artery (Figure 2(a)). A 130-cm 5-Fr Simmons-shaped inner catheter was fully engaged with the left common carotid artery (Figure 2(b)) and navigated into the left internal carotid artery with a 180-cm soft-tipped 035-inch hydrophilic wire under a roadmap after left common carotid angiography. We then attempted to direct the guiding sheath coaxially with the inner catheter from the left common carotid artery to the left internal carotid artery; however, it slipped down into the aortic arch and could not be guided. The patient was eventually converted from transradial approach to transfemoral approach and coil embolization was completed (Figure 2(c)).

Figure 2.

Figure 2.

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Illustrative case of access site crossover from transradial approach to transfemoral approach. A 78-year-old woman with left posterior communicating artery aneurysm had difficulty navigating the guiding sheath into the left internal carotid artery cervical segment. Three-dimensional computed tomography angiography showed an acute angle (α) between the innominate artery and the left common carotid artery (A). A 130-cm 5-Fr Simmons-shaped inner catheter was fully engaged with the left common carotid artery (B) and navigated into the left internal carotid artery with a 180-cm soft-tipped 035-inch hydrophilic wire under a roadmap after left common carotid angiography. We then attempted to direct the guiding sheath coaxially with the inner catheter from the left common carotid artery to the left internal carotid artery; however, it slipped down into the aortic arch and could not be guided. The patient was eventually converted from transradial approach to transfemoral approach and coil embolization was completed (C). (A): Three-dimensional computed tomography angiography, (B, C): Left common carotid angiography. Arrow: 6-Fr straight-shaped guiding sheath (FUBUKI Dilator Kit), arrowhead: a 130-cm 5-Fr Simmons-shaped catheter, α: angle formed by the innominate artery and the left common carotid artery.

Discussion

In the last few years, in the fields of neuroendovascular surgery and cardiovascular surgery, TRA has been spreading worldwide due to its minimally invasive nature and low risk of complications. Previous case reports and cohort studies have verified the feasibility of the TRA as an access route for intracranial aneurysm embolization.4,7,13,39,40

However, few studies have compared TRA and TFA in terms of therapeutic efficacy and complications in cohorts of patients who underwent coil embolization for UIAs. The present study showed that TRA was associated with a significantly lower incidence of minor ASCs than TFA by propensity-adjusted analyses. On the other hand, no significant difference in fluoroscopy time or VER was seen between TRA and TFA groups.

Complications

The present study demonstrated that TRA offered a significantly reduced rate of minor ASCs compared with TFA, even after propensity adjustment. In the field of interventional cardiovascular surgery, a meta-analysis of 76 trials (15 randomized trials, 61 observational trials) comparing TRA and TFA in a total of 761,919 patients showed that TRA reduced bleeding by 78% and the need for blood transfusion by 80%. 41 Neuroendovascular treatment requires a larger-diameter guiding catheter than cardiovascular treatment, which may increase the risk of complications at the puncture site. In addition, coil embolization for UIAs has been increasing in the placement of intracranial stents and flow-diverters for wide-necked or large aneurysms. Dual-antiplatelet therapy is essential for stents and flow-diverters. These factors may lead to increases in hemorrhagic complication rates at the puncture site. In fact, in the present study, dual-antiplatelet agents were administered 2 weeks prior to treatment in all patients in case stent assistance was necessary; 25 access-related hemorrhagic complications were observed in TFA, but only one in TRA. In a meta-analysis of 17 neurointerventional trials (2 randomized trials, 15 observational trials) regarding ASCs among a total of 2767 patients with TRA and 5222 patients with TFA, Schartz et al. 42 reported a composite ASC rate of 1.8% (49/2767) for TRA and 3.2% (168/5222) for TFA (p < 0.001), and concluded that TRA had a lower incidence of ASCs than TFA. A literature review limited to the treatment of intracranial aneurysms via TRA similarly demonstrated low incidences of minor ASCs, ranging from 0% to 5.0% (Table 4).4,5,7,13,30,31,39,40,43-49 TRA can be expected to reduce minor ASCs.

Table 4.

Main literature review (case series of more than 10 cases) for intracranial aneurysm treatment via TRA.

Characteristic Goland et al., 2017 39 Snelling et al., 2019 7 Chen et al., 2019 4 Khanna et al., 2019 5 Sweid et al., 2019 43 Mouchtouris et al., 2019 44 Chivot et al., 2019 13 Almallouhi et al., 2020 45 Hanaoka et al., 2020 40 Li et al., 2021 30 Waqas et al., 2021 46 Weinberg et al., 2021 31 Kuhn et al., 2021 47 Son et al., 2021 48 Adeeb et al., 2021 49 Present study
n 40 33 49 33 18 10 64 284 103 134 35 32 32 10 20 37
Unruptured 7 (18) N/A N/A 28 (85) N/A N/A 31 (48) N/A 82 (80) N/A N/A N/A N/A 7 (70) 13 (65) 37 (100)
Embolization technique
 Primary coiling 35 (87.5) 12 (36) 0 (0) 16 (48) 0 (0) 1 (10) 34 (53) 97 (34) 31 (30) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 9 (24)
 Balloon-assisted 0 (0) 3 (9.1) 0 (0) 0 (0) 0 (0) 0 (0) 22 (34) 19 (6.7) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 7 (19)
 Double-catheter 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 37 (36) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0)
 Stent-assisted 0 (0) 6 (18) 0 (0) 4 (12) 0 (0) 0 (0) 6 (9.4) 57 (20) 35 (34) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 21 (57)
 Flow diverter 5 (12.5) 11 (33) 49 (100) 13 (39) 18 (100) 2 (20) 2 (3.1) 89 (31) 0 (0) 134 (100) 35 (100) 32 (100) 32 (100) 0 (0) 0 (0) 0 (0)
 Woven EndoBridge 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 6 (60) 0 (0) 22 (7.7) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 10 (100) 20 (100) 0 (0)
 PulseRider 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 1 (10) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0)
 Vessel sacrifice 0 (0) 1 (3.0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0)
Embolization result (MRRC)
 Class I N/A N/A N/A 10 (50) N/A N/A N/A N/A 35 (34) N/A N/A N/A N/A N/A 11 (55) § 16 (43)
 Class II N/A N/A N/A 7 (35) N/A N/A N/A N/A 39 (38) N/A N/A N/A N/A N/A 4 (20) § 15 (41)
 Class IIIa N/A N/A N/A 3 (15) N/A N/A N/A N/A 29 (28) N/A N/A N/A N/A N/A 0 (0) § 2 (5.4)
 Class IIIb N/A N/A N/A 0 (0) N/A N/A N/A N/A 0 (0) N/A N/A N/A N/A N/A 5 (25) § 4 (11)
Access-related complications 0 (0) N/A 0 (0) 1 (3.0) 0 (0) 0 (0) 0 (0) 2 (0.7) 2 (1.9) 0 (0) 0 (0) 0 (0) 1 (3.1) 0 (0) 1 (5.0) 2 (5.4)
 Minor † 0 (0) N/A 0 (0) 1 (3.0) 0 (0) 0 (0) 0 (0) 2 (0.7) 2 (1.9) 0 (0) 0 (0) 0 (0) 1 (3.1) 0 (0) 1 (5.0) 1 (2.7)
 Major †† 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 (0) 0 0 (0) 0 (0) 1 (2.7)
Non-access-related complications ††† N/A 1 (3.0) 0 (0) 0 (0) N/A 0 (0) 5 (7.8) N/A 0 (0) 5 (3.7) 1 (2.9) 0 (0) N/A 0 (0) 3 (15) 2 (5.4)
Open in a new tab

MRRC, modified Raymond-Roy classification; N/A, not available.

†Minor access-related complications included forearm hematoma that improved with local compression, asymptomatic radial artery occlusion, and superficial hematoma causing pain/discomfort.

††Major access-related complications included compartment syndrome due to radial artery perforation.

†††Non-access site complications included cerebral thromboembolic and hemorrhagic events.

§Complete occlusion (100%), near-complete (90-99%) and partial (<90%) occlusion were counted as Class I, Class II and Class IIIb, respectively. Data represent number and percentage of patients unless otherwise indicated.

In this research, no significant difference in major ASCs was found between TRA and TFA. The TRA-related major complication, that is, compartment syndrome developed in the right forearm due to perforation of the proximal right radial artery, occurred in the second month after we started TRA procedures at our institution. After experiencing this complication, in cases in which the guiding catheter is trapped due to radial artery spasm, anti-spasmolytic agents are infused into the artery to prevent similar complications from occurring. According to the literature for cardiology, in general, adequate experience (experience with more than 50 surgical cases) is required to reduce complications and crossover rates, 50 and similar concepts are likely applicable to the field of neuroradiology. As we all know, care must be taken to avoid ASCs, especially for surgeons inexperienced in TRA.

Furthermore, in the present study, no significant difference between TRA and TFA was seen in terms of non-ASCs. According to a previous meta-analysis, no significant difference in non-ASCs was found between TRA and TFA (p = 0.28). 42 Coil embolization for UIAs via TRA can reduce risk of minor ASCs without increasing the risk of non-ASCs compared with conventional TFA.

Fluoroscopy time

In the present study, no difference was observed between TRA and TFA in terms of fluoroscopy time after propensity adjustment. Catapano et al. 8 showed that although TRA was associated with a longer fluoroscopy time than TFA, the most recent 18 treatments (mean time, 36 min) were shorter than the first 40 treatments (mean time, 41 min), indicating that procedure time decreases as experience accumulates. The same authors, with more experience, subsequently showed no significant differences in fluoroscopy time between TRA and TFA. 51 In addition, Kanna et al. showed that fluoroscopy time was shorter in TRA than in TFA among 98 patients who underwent diagnostic angiography by TRA and TFA. The shorter fluoroscopy time with TRA was probably due to the operator having a wealth of experience with TRA. 5 Increasing experience with TRA treatment may be an essential factor in reducing fluoroscopy time.

Therapeutic efficacy

The present study found no significant difference between TRA and TFA with regard to VER after propensity adjustment. Our experience has shown that TRA and TFA allowed complete embolization of aneurysms in the same fashion after the guiding catheter reached the target vessel. This means that once the guiding catheter has been guided into the target vessel, TRA is similar to TFA in terms of embolization technique, including primary coiling, balloon-assisted, double-catheter, and stent-assisted methods. Furthermore, the embolization result (MRRC) also did not differ significantly between groups. Treatment with TRA allows coil embolization comparable to TFA.

Crossover

In our series, eight patients (18%) required a change from TRA to TFA due to the acute angle at the origin of the CCA (Figure 2). If the angle between the innominate artery and CCA is highly acute, endovascular access route to the CCA via TRA for neurointervention is more difficult than with a wide angle.4,7,13,22,52-58 A systematic review of TRA for neurointerventions reported a crossover rate to TFA of 4.8%. 58 Compared with previous reports, the TRA crossover rate in the present study was higher, attributable to the following three reasons. First, previous reports of low crossover rates were influenced by selective bias because of the retrospective design of the studies.59-62 In other words, in those studies, TFA was selected for patients in who TRA was assumed likely to prove difficult. According to a study of 121 consecutive patients who received diagnostic and interventional neurovascular treatment using a “radial-first” approach at a single center, the transfemoral crossover rate was approximately 25%. 14 Another study showed that 10 of 49 (20%) consecutive patients who underwent flow diversion with TRA were converted to TFA. 4 At our institution, since March 2021, all patients with a radial artery diameter ≥2.0 mm and a positive Allen test have been consecutively embolized via TRA. This may have contributed to the relatively high crossover rate compared with previous reports. A second reason is that we guided a straight-shaped guiding sheath (FUBUKI Dilator Kit; Asahi Intecc) designed specifically for TFA in all cases of TRA, which made it difficult to guide the catheter to the target vessel with a steep bifurcation angle. Hanaoka et al. reported that in coil embolization of aneurysms in the anterior circulation with TRA, the crossover rate was 0% using a guiding sheath (Axcelguide STIFF-J; Medikit), which was suitable for TRA.40,63,64 In the future, the crossover rate could be reduced by adopting the methods and guiding sheaths described by Hanaoka et al. At present, devices applicable to TRA remain limited, and more devices specifically tailored to TRA need to be developed.4,7,13,58 Third, as described above, further experience with TRA is necessary to acquire skill, raising the learning curve. 50 In fact, the crossover from TRA to TFA in the present study was mostly observed in the early stages of treatment after switching to the “TRA-first” approach. Until the operator becomes familiar with TRA, assistance from a proficient supervisor or appropriate selection of patients treated via TRA should be required.

Limitations

The limitations of the present research were the small number of patients and non-randomized, retrospective nature of the study. Furthermore, in the present study, the TRA procedure was performed uniformly, but only by two surgeons (M.F. and R.T.). Therefore, future prospective, randomized, multicenter studies with larger numbers of patients are warranted to evaluate the efficacy and complications of TRA more objectively. Propensity-adjusted analysis was performed based on previous reports of cardiovascular interventional treatment, limited to age, sex, aneurysm volume, embolization technique, and sheath size, each of which might represent confounding factors for efficacy and complications in TRA.65,66 In addition, although both the radial and femoral arteries were punctured in eight patients (8/45, 18%) due to crossover from TRA to TFA, we did not encounter any ASCs associated with radial artery puncture. The frequency of ASCs, which was not overestimated in crossover cases, thus did not have any impact on clinical outcomes of TFA.

Conclusions

Coil embolization for UIAs via TRA can reduce risk of minor ASCs without increasing the risk of non-ASCs compared with conventional TFA, and can achieve comparable results in term of efficacy and fluoroscopy time. A “TRA-first” strategy can represent a valid option for coil embolization of UIAs.

Appendix.

Abbreviations and Acronyms

ASC

Access site complication

CCA

Common carotid artery

MRRC

Modified Raymond-Roy classification

TFA

Transfemoral approach

TRA

Transradial approach

UIA

Unruptured intracranial aneurysm

VER

Volume embolization ratio

Footnotes

Author contributions: All authors listed on the title page have contributed sufficiently to the research project to be included as authors, have reviewed the manuscript.

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding: The author(s) received no financial support for the research, authorship, and/or publication of this article.

Ethical approval: The research permission approved by the local institutional review board of the Jikei University School of Medicine (29–228 (8844)).

Informed consent: The local institutional review board waived the need to obtain a formal consent form due to this retrospective registry study.

ORCID iDs

Michiyasu Fuga https://orcid.org/0000-0002-0517-6617

Toshihide Tanaka https://orcid.org/0000-0002-6474-6317

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