BACKGROUND:
Transradial access (TRA) recently has gained popularity among neurointerventionalists. However, hesitation to its use for mechanical thrombectomy (MT) remains.
OBJECTIVE:
To evaluate and describe the evolution of TRA for MT.
METHODS:
We performed a retrospective analysis of patients undergoing TRA for MT. We performed a chronological ternary analysis to assess the impact of experience. We assessed the impact of a guide catheter designed specifically for TRA.
RESULTS:
We identified 53 patients who underwent TRA for MT. There was a statistically significant decrease in contrast use (148.9 vs 109.3 vs 115.2 cc), procedure time (62.4 vs 44.7 vs 41.3 minutes), fluoroscopy time (39.2 vs 44.7 vs 41.3 minutes), and puncture-to-recanalization time (40.6 vs 27.3 vs 29.4) over time. There was trend toward improved thrombolysis in cerebral infarction ≥ 2b recanalization rate (72.2% vs 77.8% vs 100%) over time. The introduction of a radial-specific catheter had a statistically significant positive impact on contrast use (133.8 vs 93 cc, P = .043), procedure time (54.2 vs 36.4 minutes, P = .003), fluoroscopy time (33.7 vs 19.8 minutes, P = .004), puncture-to-recanalization time (35.8 vs 25.1 minutes, P = .016), and thrombolysis in cerebral infarction ≥ 2b recanalization rate (71.4% vs 100%, P = .016).
CONCLUSION:
TRA is a safe and effective route of endovascular access for MT. Experience with this technique improves its efficacy and efficiency. The introduction of a TRA-specific catheter expands the armamentarium of the neurointerventionalist and may facilitate lesion access during MT procedures. Continued development of radial-specific devices may further improve MT outcomes.
KEY WORDS: Access, Endovascular, Mechanical thrombectomy, Stroke
ABBREVIATIONS:
- ACA
anterior cerebral artery
- ANOVA
analysis of variance
- AP
anteroposterior
- DSA
digital subtraction angiography
- ESCAPE
Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion with Emphasis on Minimizing CT to Recanalization Times
- ICA
internal carotid artery
- MCA
middle cerebral artery
- MT
mechanical thrombectomy
- NA
not applicable
- REVASCAT
Randomized Trial of Revascularization with Solitaire FR Device Versus Best Medical Circulation Large Vessel Occlusion Presenting Within 8 Hours of Symptom Onset
- TFA
transfemoral access
- TICI
thrombolysis in cerebral infarction
- TRA
transradial access.
Transradial access (TRA) recently has gained popularity among neurointerventionalists as an alternative to transfemoral access (TFA).1-5 The attractiveness of TRA lies primarily in its safety profile and reduction in access site complications compared with TFA.6,7 However, TRA for neurointerventional procedures is not without its limitations. The smaller caliber of the radial artery compared with the femoral artery may necessitate smaller access sheaths and smaller catheters. Until recently, there were no “radial-specific” catheters; in other words, catheters whose transitions were designed for TFA were being used for TRA, which resulted in suboptimal trackability. These limitations, in addition to the learning curve inherent to any new technique, have resulted in an apprehension among neurointerventionalists to use TRA for time-sensitive mechanical thrombectomy (MT), a situation in which many prefer the use of large-bore aspiration catheters.8
When considering the advantages of TRA over TFA, patients presenting with acute ischemic stroke may be ideally suited to reap the benefits of TRA for MT. These patients frequently have comorbid conditions requiring antiplatelet therapy and/or anticoagulation. Furthermore, intravenous thrombolysis remains the standard of care for eligible patients presenting with acute ischemic stroke. These medical therapies may increase the risk of hemorrhagic access site complications or make these complications more difficult to manage when they do occur. The lower risk of these complications with TRA may make this access route particularly beneficial.
In this study, we present our case series of patients undergoing TRA for MT at our academic institute. We highlight the evolution of the technique, as our experience increased, but also as we began using devices designed specifically for TRA. In addition, we discuss lessons we have learned and technical features that have made TRA a feasible route of access for MT.
METHODS
With approval from our institutional review board, we performed a retrospective review of data for consecutive patients undergoing MT between July 2019 and January 2022 by the senior author. All patients eligible for MT were treated using TRA unless there was a clear contraindication (eg, anomalous origin of the great vessels and occluded right vertebral artery) on preprocedure imaging. All procedures were performed with the patients' or their legally authorized representatives' consents. Clinical, procedural, and radiographic data were analyzed.
Transradial Procedure
Fundamental techniques of TRA for neurointerventions have been previously reported.9 In our initial experience, 6-French (F) access was required, while later 7F access was necessary. In both cases, a 6F or 7F Glidesheath Slender (Terumo) was introduced. After confirming appropriate placement and adequate collateral flow with an injection through the sheath, a radial cocktail (verapamil 2.5 mg, nitroglycerin 200 mcg, and heparin 2000 units in patients not receiving intravenous thrombolysis) was injected.
Early in our experience, a 6F Benchmark catheter (Penumbra Inc) and Simmons select catheter (Penumbra) were advanced over a 0.035-in Glidewire (Terumo). Reconstitution of the Simmons select catheter has been previously described.9 The target vessel was selected, and the Benchmark catheter was advanced into the distal cervical segment of the appropriate artery. Combination therapy with aspiration and a retrievable stent was used. Given the size of the Benchmark guide catheter, we used a 5F Sofia aspiration catheter (Microvention).
Later in our experience, a 7F Rist catheter (Medtronic) and Simmons select catheter (Medtronic) were used. The target vessel was selected, and the Rist catheter was advanced into the distal cervical or proximal intracranial segment of the appropriate artery. Combination therapy with aspiration and a retrievable stent was used. Owing to market availability, we initially used a 5F Sofia aspiration catheter (Microvention) but then transitioned to using the Red 62 aspiration catheter (Penumbra).
Statistical Analysis
We analyzed safety and efficacy data in 2 ways. First, to assess the effect of a learning curve, we divided cases into chronological ternaries. Second, to assess the impact of the development of a catheter designed specifically for TRA (Rist catheter), we divided cases into those performed before its use and those performed after its introduction. Given that there were significantly more tandem lesions in the group after the introduction of the Rist catheter, outcome measures were analyzed with tandem lesions excluded. An independent sample t-test was used to compare continuous variables. For categorical variables, the χ2 test was used to examine group differences. We used one-way analysis of variance to assess differences between chronological tertials. Tukey HSD was our post hoc test of choice. All statistical analysis was conducted using R version 4.2.0 (R Core Team 2022. URL: https://www.R-project.org/).
RESULTS
We identified 53 patients who underwent TRA for MT. Basic demographics and background characteristics are provided in Table 1. Twenty-five (47.2%) of the patients were women. Hypertension was the most common stroke risk factor, present in 43 patients (81.1%). Intravenous thrombolysis was given in 22 cases (41.5%). The lesion was located on the left side in 29 patients (54.7%). The most common site of occlusion was the middle cerebral artery, occurring in 38 patients (71.7%). Six patients (11.3%) experienced tandem lesions. A type 2 aortic arch was the most common configuration, occurring in 35 patients (66.0%).
TABLE 1.
Basic Demographics of 53 Patients Undergoing TRA for MT
| Age (y; mean) | 64.8 |
| Female sex, n (%) | 25 (47.2) |
| Hypertension, n (%) | 43 (81.1) |
| Diabetes, n (%) | 16 (30.2) |
| Tobacco use, n (%) | 12 (22.6) |
| Prior stroke, n (%) | 14 (26.4) |
| Antiplatelet use, n (%) | 21 (39.6) |
| Anticoagulant use, n (%) | 9 (17.0) |
| Intravenous thrombolysis, n (%) | 22 (41.5) |
| Intracranial occlusion laterality, n (%) | |
| Right | 22 (41.5) |
| Left | 29 (54.7) |
| NA | 2 (3.8) |
| Intracranial occlusion location, n (%) | |
| ICA | 12 (22.6) |
| MCA | 38 (71.7) |
| ACA | 1 (1.9) |
| Basilar artery | 2 (3.8) |
| Tandem occlusion, n (%) | 6 (11.3) |
| Arch type, n (%) | |
| 1 | 9 (17.0) |
| 2 | 35 (66.0) |
| 3 | 8 (15.1) |
| Other | 1 (1.9) |
ACA, anterior cerebral artery; ICA, internal carotid artery; MCA, middle cerebral artery; MT, mechanical thrombectomy; NA, not applicable.
To assess the effect of a learning curve, we divided cases into chronological ternaries. There was a statistically significant decrease in contrast use (148.9 vs 109.3 vs 115.2 cc), mean procedure time (62.4 vs 44.7 vs 41.3 minutes), mean fluoroscopy time (39.2 vs 44.7 vs 41.3 minutes), and mean puncture-to-recanalization time (40.6 vs 27.3 vs 29.4) over time. There was trend toward improved thrombolysis in cerebral infarction (TICI) ≥ 2b recanalization rate (72.2% vs 77.8% vs 100%) over time (Table 2, Figure 1). While not statistically significant, there were trends toward fewer conversions to TFA, with 4 occurring in the first ternary and 1 in the third ternary. Similarly, there was a trend toward improved recanalization with TICI ≥ 2b occurring in 72.2%, 77.8%, and 100% in the first, second, and third ternaries, respectively. There was no statistically significant difference in the mean number of passes over time.
TABLE 2.
Procedural Outcomes Analyzed According to Chronological Thirds
| Outcome measure | Cases 1-18 | Cases 19-36 | Cases 37-53 |
|---|---|---|---|
| Contrast (cc) | 148.9 | 109.3 | 115.2 |
| Mean procedure time (min) | 62.4 | 44.7 | 41.3 |
| Mean fluoroscopy time (min) | 39.2 | 27.0 | 24.2 |
| Mean number of passes (mean) | 2.3 | 2.1 | 2.0 |
| Mean puncture-to-recanalization time (min) | 40.6 | 27.3 | 29.4 |
| Conversion to femoral, n (%) | 4 (22.2) | 0 | 1 (5.9) |
| TICI ≥ 2b recanalization, n (%) | 13 (72.2) | 14 (77.8) | 17 (100) |
TICI, thrombolysis in cerebral infarction.
FIGURE 1.
Scattered dot-plot representing A, procedure time, B, fluoroscopy time, C, and puncture-to-recanalization time in each ternary. Horizontal blue line represents mean value in each ternary, and light blue vertical bar represents SD of those values.
To analyze the impact of a catheter designed specifically for TRA, we performed a second analysis, dividing cases into those performed before the introduction of this catheter and those performed using it. There was no difference in basic clinical characteristics between the 2 groups (Table 3). Because there were significantly more tandem occlusions in the latter group, we analyzed outcome measures after excluding cases of tandem lesions. Utilization of a TRA-specific catheter had a positive impact on contrast use (133.8 vs 93 cc, P = .043), procedure time (54.2 vs 36.4 minutes, P = .003), fluoroscopy time (33.7 vs 19.8 minutes, P = .004), and puncture-to-recanalization time (35.8 vs 25.1 minutes, P = .016). There was also a statistically significant impact on recanalization rate with TICI ≥ 2b recanalization occurring in 100% of patients in whom the Rist catheter was used compared with 71.4% in those treated before its introduction (P = .016). Although not statistically significant, there was a trend toward fewer conversions to TFA, with 1 (4.2%) occurring in the Rist group and 4 (14.3%) occurring in the non-Rist group (P = .367). There was no difference in the mean number of passes.
TABLE 3.
Procedural Details and Outcomes Analyzed According to Use of the Rist Catheter. Outcomes Were Analyzed With Tandem Lesions Excluded
| Demographic | Before Rist (n = 29) | Rist (n = 24) | P-value |
|---|---|---|---|
| Hypertension, n (%) | 21 (72.4) | 22 (91.7) | .075 |
| Hyperlipidemia, n (%) | 17 (58.6) | 16 (66.7) | .547 |
| Diabetes, n (%) | 7 (24.1) | 9 (37.5) | .364 |
| Prior stroke, n (%) | 6 (20.1) | 8 (33.3) | .832 |
| Antiplatelet use, n (%) | 13 (44.8) | 13 (54.2) | .768 |
| Anticoagulant use, n (%) | 5 (17.2) | 4 (16.7) | 1 |
| Intravenous thrombolysis, n (%) | 12 (41.4) | 10 (41.7) | .983 |
| Intracranial occlusion laterality, n (%) | |||
| Right | 9 (31.0) | 12 (50.0) | |
| Left | 18 (62.1) | 12 (50.0) | |
| NA | 2 (6.9) | 0 | |
| Intracranial occlusion location, n (%) | |||
| ICA | 6 (20.7) | 6 (25.0) | |
| MCA | 20 (69.0) | 18 (75.0) | |
| ACA | 1 (3.4) | 0 | |
| Basilar artery | 2 (6.9) | 0 | |
| Tandem occlusion, n (%) | 1 (3.4) | 5 (20.8) | |
| Arch type, n (%) | |||
| 1 | 5 (17.2) | 4 (16.7) | |
| 2 | 18 (62.1) | 17 (70.8) | |
| 3 | 6 (20.7) | 2 (8.3) | |
| Other | 0 | 1 (4.2) |
| Outcome measure* | Before Rist (n = 28) | Rist (n = 19) | P-value |
|---|---|---|---|
| Contrast (cc) | 133.8 | 93.0 | .043 |
| Mean procedure time (min) | 54.2 | 36.4 | .003 |
| Mean fluoroscopy time (min) | 33.7 | 19.8 | .004 |
| Mean number of passes (mean) | 2.3 | 1.6 | .058 |
| Mean puncture-to-recanalization time (min) | 35.8 | 25.1 | .016 |
| Conversion to femoral, n (%) | 4 (14.3) | 1 (4.2) | .367 |
| TICI ≥ 2b recanalization, n (%) | 20 (71.4) | 19 (100) | .016 |
ACA, anterior cerebral artery; ICA, internal carotid artery; MCA, middle cerebral artery, NA, not applicable; TICI, thrombolysis in cerebral infarction.
Outcomes were analyzed after excluding cases of tandem lesions.
In this series of 53 patients undergoing TRA for MT, there were no access site complications.
DISCUSSION
In this article, we describe the evolution of TRA for MT at a single institute. Analyzing the data in 2 ways (according to chronological ternary and before/after the introduction of a catheter designed specifically for TRA), we aimed to describe both the effects of a learning curve with TRA, as well as those of new technology, namely a TRA-specific catheter. We found a decrease in contrast use procedure time, fluoroscopy time, and puncture-to-recanalization time and improved TICI ≥ 2b recanalization rate over time. We found a decrease in contrast use, procedure time, fluoroscopy time, and puncture-to-recanalization time and improved TICI ≥ 2b recanalization rate after the routine use of a TRA-specific catheter. However, given that our experience increased and the introduction of this catheter occurred simultaneously (ie, in the latter half of our series), it is not possible to ascribe the observed improvements to one factor or the other in isolation.
Our analysis-based chronological ternaries showed a statistically significant decrease in contrast media usage, procedure time, fluoroscopy time, and puncture-to-recanalization time over time and a trend toward improved TICI ≥ 2b recanalization rate. This is in keeping with data from the National Cardiovascular Data Registry describing the learning curve associated with TRA for percutaneous coronary interventions and supports the positive influence of increasing experience.10 Although our data pertain only to MT performed using TRA, the effect of experience has been reported for MT performed from TFA.11,12 Taken together, these findings suggest that the learning curve for MT using TRA may be steep and, therefore, should be pursued by neurointerventionalists experienced in both MT and TRA for other neurointerventional procedures.
The Rist Access System (Medtronic) was introduced in the latter half of our series and is the first catheter specifically designed for and approved by the US Food and Drug Administration for TRA neurointerventional procedures.7 It consists of a 0.79-inch guide catheter and 5F select catheter. The guide catheter is introduced into the radial artery through a 7F sheath—Glidesheath slender (Terumo) or Prelude Ideal (Merit). The transitions of the guide catheter are designed specifically to enhance delivery of the catheter into the great vessels from the radial artery.7
Introduction of a catheter designed specifically for TRA had a statistically significant positive impact on contrast media utilization, procedure time, fluoroscopy time, puncture-to-recanalization time, and TICI ≥ 2b recanalization rate. Although not statistically significant, there were fewer transitions to TFA in following the introduction of the Rist catheter. This is likely due to the fact that the Rist guide catheter has transitions specifically designed for TRA. Before introduction of this catheter, guide catheters with transitions optimized for TFA were simply being used with TRA. Therefore, in certain anatomic configurations of the aortic arch, these transitions likely were suboptimal for tracking the catheter, leading to its herniation into the aortic arch.
The effective recanalization rates (TICI ≥ 2b) observed in our series compare favorably with those reported in previous series in which MT was performed using TFA. TICI ≥ 2b was observed in 88% of patients in SWIFT PRIME, 72% of patients in Endovascular Treatment for Small Core and Anterior Circulation Proximal Occlusion with Emphasis on Minimizing CT to Recanalization Times (ESCAPE), 66% of patients in Randomized Trial of Revascularization with Solitaire FR Device Versus Best Medical Circulation Large Vessel Occlusion Presenting Within 8 Hours of Symptom Onset (REVASCAT), and 86% in EXTEND-IA.13-16 The effective recanalization rates of patients in last chronological ternary (100%) and in whom the Rist catheter was used (100%) were higher compared with previously reported series.
Tandem Lesions
Owing to their inherent complexity and necessary increased time requirement, we elected to exclude tandem lesions from statistical analysis to more clearly compare outcome measures between groups. However, we find value in discussing this subgroup of complex patients. Our series includes 5 tandems lesions, 4 of which were treated with carotid artery stenting and thrombectomy. Procedural details for these cases are described in Table 4. In all cases of carotid artery stenting, the stent was successfully deployed, but in 1 case, recanalization of the intracranial lesion was not achieved. The mean time from puncture-to-recanalization in the 4 cases with successful recanalization was 37 minutes. These cases demonstrate that TRA can be used to treat tandem lesions effectively. It is also worth noting that when including the tandem lesions in our analysis, the difference in fluoroscopy time, procedure time, and puncture-to-recanalization time maintained its statistical significance.
TABLE 4.
Procedural Details and Outcomes of Tandem Lesions Treated Using TRA
| Case no. | Laterality | Guide catheter | Carotid stent | Recanalization (TICI) | Procedure time (min) | Fluoroscopy time (min) | Puncture-to-recanalization time (min) |
|---|---|---|---|---|---|---|---|
| 16 | Left | Benchmark | Wallstent 8 × 29 mm | 3 | 80 | 35.4 | 50 |
| 31 | Left | Rist | Wallstent 8 × 29 mm | 0 | 127 | 106 | NA |
| 44 | Left | Rist | Wallstent 10 × 24 mm | 2b | 56 | 42.9 | 44 |
| 45 | Left | Rist | NA | 2c | 42 | 22.3 | 33 |
| 46 | Right | Rist | Wallstent 8 × 29 mm | 2c | 34 | 22.5 | 21 |
NA, not applicable; TICI, thrombolysis in cerebral infarction; TRA, transradial access.
Description of Conversion to Femoral
Although not a statistically significant difference, there was only 1 (4.2%) conversion to TFA in the Rist group, compared with 4 (14.3%) in the non-Rist group. The conversions to TFA in the non-Rist group were all related to the inability to advance the guide catheter into the cervical internal carotid artery because of herniation of the system into the aortic arch.
The conversion to TFA that occurred in the Rist group occurred in a patient who experienced a right middle cerebral artery occlusion in the setting of an aberrant right subclavian artery and mild tortuosity of the carotid siphon (Figure 2A). In this case, the 95-cm guide catheter tracked to the proximal ICA (Figure 2B). We were able to reach the lesion, although with the lack of support from the guide catheter (due to its very proximal location), the mild tortuosity of the carotid siphon presented an unexpected challenge to microcatheterization and crossing the lesion (Figure 2C). We performed the first pass from the TRA, but given the challenge in reaching the lesion, we converted to TFA and performed the second pass (Figure 2D). In considering this case, another option, rather than converting to TFA, would have been to introduce the longer (105 cm) Rist guide catheter, which would have tracked more distally into the cervical internal carotid artery and potentially offered more support. This case also highlights the importance of thorough consideration of the preoperative computed tomography angiography to identify patients with anatomic anomalies that may make TRA less favorable.
FIGURE 2.
Depiction of case with aberrant subclavian artery in which conversion to TFA was performed. A, Coronal CTA in which the aberrant anatomy was not visualized because the image did not include the aortic arch. B, AP DSA of the right internal carotid artery demonstrating the distal most location of the Rist catheter (arrow) in the proximal internal carotid artery. There is a right M1 occlusion. C, The course of the microcatheter is depicted by the dashed line. The distal end of the microcatheter (star) is in the proximal M2 segment. D, AP DSA demonstrating the distal most location of the guide catheter (arrow) after switching to TFA. AP, anteroposterior; DSA, digital subtraction angiography; TFA, transfemoral access.
Access Site Complications
We experienced no access site complications in this series of 53 patients undergoing MT through TRA. As has been discussed previously, patients undergoing MT may be ideally suited to reap the benefits of TRA because intravenous thrombolysis remains the standard of care for eligible patients.17,18 In addition, the frequent presence of cardiovascular, peripheral vascular, and/or cerebrovascular comorbidities necessitating treatment with antiplatelet or anticoagulant medications further places these patients at risk for access site complications.
In the present series, 22 patients (41.5%) received intravenous thrombolysis, 21 patients (39.6%) were taking antiplatelet medication, and 9 patients (17%) were on anticoagulation. The fact that there were no access site complications despite these iatrogenic risk factors emphasizes the safety benefits of TRA. Taking these data in the context of the SWIFT PRIME, ESCAPE, REVASCAT, and EXTEND-IA trials, which reported a 2% to 12% incidence of severe access-related adverse events, further underscores the opportunity for improvement in the safety profile of MT with TRA.13-15,19
Limitations
The present series is a retrospective analysis of consecutive patients who underwent MT using TRA at a single center by a single surgeon (SAM). Therefore, it is limited by the biases inherent to the study design and the practice patterns of the institute and surgeon. Similarly, the learning curve presented here is one of a single surgeon; therefore, the slope and influence of the learning curve undoubtedly will vary among other operators. As we previously mentioned, the introduction of the TRA-specific catheter occurred as our experience was increasing. After its introduction, it was used exclusively as the guide catheter for MT with TRA. Therefore, it is not possible to ascribe the improvements observed in the latter half of this series and in the Rist group to one factor or the other in isolation. It is possible that each variable influenced the other and that these influences were synergistic.
It should be noted that in the present series, the radial-specific catheter had an inner diameter of 0.079 inches. Therefore, the diameter of the aspiration catheter was smaller than could be used in a larger diameter guide catheter. When using the ADAPT technique, a plateau effect of aspiration catheter size and efficacy has been reported, with medium-bore aspiration catheters performing and large-bore aspiration catheters.20 While the effect of aspiration catheters size on the efficacy of combination therapy is less well defined, the strong recanalization rates reported in the present series may echo those seen with ADAPT. Nonetheless, this limitation is important to recognize when implementing TRA for MT.
CONCLUSION
TRA is a safe and effective alternative to TFA for patients undergoing MT. Increasing experience with TRA and the introduction of a TRA-specific catheter positively influence procedural outcomes of MT. Continued experience with TRA and the development of TRA-specific devices are warranted.
Acknowledgments
We acknowledge Ethan Ritz for assistance with statistical analysis.
Contributor Information
Ruth S. Saganty, Email: ruth_s_saganty@rush.edu.
Krishna C. Joshi, Email: krishna_c_joshi@rush.edu.
Yazan Radaideh, Email: yazan_radaideh@rush.edu.
Funding
The authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
Disclosures
Dr Munich performs proctoring services for Medtronic. The other authors have no personal, financial, or institutional interest in any of the drugs, materials, or devices described in this article.
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