Article Text

Case series
Versatile use of catheter systems for deployment of the Pipeline embolization device: a comparison of biaxial and triaxial catheter systems
  1. Kunal Vakharia1,2,
  2. Muhammad Waqas1,2,
  3. Hakeem J Shakir1,2,
  4. Felix Chin1,2,
  5. Joelle N Hartke1,
  6. Hussain Shallwani1,2,
  7. Jeffrey S Beecher1,2,
  8. Adnan H Siddiqui2,3,
  9. Elad I Levy2,3
  1. 1 Department of Neurosurgery, University at Buffalo School of Medicine and Biomedical Sciences, Buffalo, New York, USA
  2. 2 Department of Neurosurgery, Gates Vascular Institute, Buffalo, New York, USA
  3. 3 Departments of Neurosurgery and Radiology and Canon Stroke and Vascular Research Center, University at Buffalo, State University of New York, Buffalo, New York, USA
  1. Correspondence to Dr Elad I Levy, Department of Neurosurgery, University at Buffalo, Buffalo, NY 14203, USA; ELevy{at}


Background A Pipeline embolization device (PED; Medtronic, Dublin, Ireland) can be deployed using either a biaxial or a triaxial catheter delivery system.

Objective To compare the use of these two catheter delivery systems for intracranial aneurysm treatment with the PED.

Methods A retrospective study of patients undergoing PED deployment with biaxial or triaxial catheter systems between 2014 and 2016 was conducted. Experienced neurointerventionalists performed the procedures. Patients who received multiple PEDs or adjunctive coils were excluded. The two groups were compared for PED deployment time, total fluoroscopy time, patient radiation exposure, complications, and cost.

Results Eighty-two patients with 89 intracranial aneurysms were treated with one PED each. In 49 cases, PEDs were deployed using biaxial access; triaxial access was used in 33 cases. Time (min) from guide catheter run to PED deployment was significantly shorter in the biaxial group (24.0±18.7 vs 38.4±31.1, P=0.006) as was fluoroscopy time (28.8±23.0 vs 50.3±27.1, P=0.001). Peak radiation skin exposure (mGy) in the biaxial group was less than in the triaxial group (1243.7±808.2 vs 2074.6±1505.6, P=0.003). No statistically significant differences were observed in transient and permanent complication rates or modified Rankin Scale scores at 30 days. The triaxial access system cost more than the biaxial access system (average $3285 vs $1790, respectively). Occlusion rates at last follow-up (mean 6 months) were similar between the two systems (average 88.1%: biaxial, 89.2%: triaxial).

Conclusion Our results indicate near-equivalent safety and effectiveness between biaxial and triaxial approaches. Some reductions in cost and procedure time were noted with the biaxial system.

  • aneurysm
  • catheter
  • flow diverter
  • technique
  • technology

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.


Successful deployment of the Pipeline embolization device (PED; Medtronic Dublin, Ireland) for intracranial aneurysm treatment requires stable proximal access, allowing maximal distal control for intracranial navigation.1 Tortuous anatomy provides challenges in neuroendovascular cases that neurointerventionalists often overcome by using larger guide catheters for more support proximally, in combination with an intermediate catheter to provide distal support for intracranial navigation (triaxial access). Without triaxial access, there have been examples in the literature of poor control and erratic behavior of the microcatheters within the vessel lumens.2 3 This has led to the preferential use of triaxial access by many neurointerventionalists.2–6 In most of these cases, the intermediate catheter is a 0.058 inch Navien intracranial support catheter (Medtronic), which provides intracranial support to the microcatheter for better control.2–6 In contrast, a biaxial system consisting of a guide catheter and microcatheter without the addition of an intermediate catheter can provide stability at lower cost for devices, concurrently reducing procedure time and risk of thromboembolic complications.7 8 As more advanced guide catheters and microcatheters are developed which provide more stable support and improved distal micronavigation, triaxial access has become less of a requirement for the deployment of a PED. Early reports on the use of new biaxial catheter systems for PED deployment have been favorable.7 8 However, no study has provided a direct comparison of the effectiveness, safety, and cost of biaxial and triaxial systems.

The high volume of PED deployment for intracranial aneurysm treatment and different techniques and methodologies applied by staff neurointerventionalists affords our center a unique opportunity to compare biaxial and triaxial access approaches. The primary objectives of our study were to compare PED deployment time, fluoroscopy time, radiation exposure to the patient, and complication rates for the two systems. Our secondary objective was to compare the costs of these two catheter systems and the modified Rankin Scale (mRS) scores of the catheter-system patient groups at follow-up 30 days after the procedure, and eventual angiographic outcome.


This retrospective cohort study was conducted at a high-volume cerebrovascular center. The study was approved by our institutional review board. Written consent for the PED procedure was obtained from each patient. Patients were included in this study if they underwent treatment of at least one intracranial aneurysm with a single PED using either biaxial or triaxial access between June 2014 and October 2016, irrespective of the size, location, or type of aneurysm. All biaxial procedures were performed by one senior operator, and all triaxial procedures by a second senior operator. Each operator had more than one decade of experience in endovascular neurosurgery. Patients who had more than one PED deployed during the same procedure and those in whom an additional therapeutic procedure (eg, coiling) was performed during the PED procedure were excluded from the study. These cases were excluded to avoid the confounding effect of additional PEDs or processes on the duration of the procedure. To account for delays due to difficult supra-aortic access, the time from the first guide catheter run after navigating the aortic arch to the deployment of the PED was calculated.

Protocol for PED deployment

Patients in whom a PED procedure was planned were started on a daily regimen of 325 mg of aspirin and 75 mg of clopidogrel orally 7 days before the PED procedure. Patients who had a P2Y12 response test with a value >200 were considered clopidogrel non-responders and were prescribed a loading dose of 180 mg of ticagrelor orally followed by 90 mg twice daily. These patients received a reduced aspirin dose of 81 mg orally once daily. Most procedures were performed under conscious sedation with midazolam and fentanyl along with a local anesthetic for groin access. Common femoral artery access was obtained with a 6 French (F) short sheath for biaxial cases and an 8 F short sheath for triaxial cases. Biaxial access was performed with a 6 F guide catheter, such as an Envoy DA XB guide catheter (DePuy Synthes, West Chester, Pennsylvania, USA). Triaxial access was usually performed with an 8 F guide catheter (6 F long sheath), such as Neuron MAX (Penumbra) or Cook Shuttle (Cook Inc., Bloomington, Indiana, USA). A 0.027 inch microcatheter, such as Marksman (Medtronic) or Excelsior XT-27 (Stryker Neurovascular, Fremont, California, USA), was used with a 0.014 inch microwire, such as a Synchro 2 (Stryker Neurovascular). A 0.058 inch Navien was used as an intermediate catheter in the triaxial system. The different catheters used in the series were recorded. An illustration of biaxial and triaxial systems is provided in figure 1, and angiographic images of representative cases in which the systems were used are shown in figures 2 and 3.

Figure 1

Schematic illustration of triaxial (left) and biaxial (right) catheter systems. University at Buffalo Neurosurgery (December 15, 2018).

Figure 2

(A) Three-dimensional angiogram showing a left superior hypophyseal artery aneurysm (arrow). (B) Anteroposterior and (C) lateral angiographic images showing the deployment of a Pipeline embolization device (PED; Medtronic, Minneapolis, Minnesota, USA) (solid arrow) using a biaxial system. The Marksman (Medtronic) microcatheter without any intermediate catheter is indicated with open arrows. The guide catheter is not visible in the picture.

Figure 3

(A) Three-dimensional angiogram showing an ophthalmic artery aneurysm (arrow). (B) Anteroposterior and (C) lateral angiographic images showing deployment of a Pipeline embolization device (solid black arrow) using a triaxial system consisting of a microcatheter (white arrow), intermediate catheter (0.058 inch Navien (Medtronic); black arrow), and 6 French Neuron MAX guide catheter (Penumbra, Alameda, California, USA) (open arrows).

Before micronavigation and PED deployment, systemic intravenous heparin was administered. An activated coagulation time of >250 s was confirmed to minimize thromboembolic complications. After the procedure, the patients were maintained on dual antiplatelet therapy for 6 months.

Data collection

A retrospective review of our database was performed to collect patient demographics, clinical presentation, aneurysm location, aneurysm morphology, biaxial or triaxial access, time interval from guide-catheter injection to PED deployment, total fluoroscopy time, periprocedural complications, aneurysm occlusion rates at 6, 12 months, and last angiographic follow-up, mRS score at last follow-up (>12 months), and cost of the catheter systems. If data were not entered into the database, this information was obtained from patient medical records.

Data analysis

Statistical analysis of the data was performed using the Statistical Package for the Social Sciences (SPSS), version 24 (IBM, Chicago, Illinois, USA). A descriptive analysis of demographics, clinical characteristics, and aneurysmal morphology for each catheter system group was performed. Categorical data were presented as percentages and proportions. Numerical data with a normal distribution were presented as means and SD; skewed data were presented as median and range. An independent-sample t-test was used to compare continuous variables. A chi-square test was used to compare categorical data. Median values between the two groups for variables with more than one category were compared using a Kruskal-Wallis H test. A P value of <0.05 was considered significant. A multivariate analysis was performed to determine the predictors associated with procedure time (guide-catheter run to PED deployment) and fluoroscopy time.


One hundred and seven patients underwent PED procedures during the study period. In 23 instances more than one PED was required, and these patients were excluded. After exclusion of these 23 cases, 82 patients with 89 aneurysms treated with 82 PED procedures met the study eligibility criteria. In seven patients, two aneurysms were treated with a single PED. Forty-nine procedures were performed using a biaxial system, and 33 procedures using a triaxial system. In 3 (6.1%) of 49 instances, the biaxial system was exchanged for a triaxial system owing to difficulty in negotiating a tortuous internal carotid artery. The mean±SD age of the patients in the catheter system groups were comparable (55.8±14.3 years in the biaxial group vs 56.0±13.1 years in the triaxial group). The cavernous and paraclinoid segments of the internal carotid artery were the most common aneurysm locations in both groups. Most aneurysms were unruptured (91.8% biaxial group vs 66.7% triaxial group). Baseline clinical characteristics and aneurysm location details for both groups are presented in table 1.

Table 1

Baseline clinical characteristics

The biaxial technique was performed mostly using the Envoy DA XB guide catheter (in 67.3% of cases). The most commonly used guide catheter in the triaxial group was the Neuron MAX (in 87.9% of cases). All triaxial procedures were performed using a Navien 0.058 inch intermediate catheter. A Marksman microcatheter was used in 97.0% of cases in the triaxial group. In the biaxial group, it was used in 59.2% of cases, followed by the Excelsior XT-27, which was used in 36.7% of cases. Details of the procedures and catheters are shown in table 2. The average cost of a biaxial system was $1790 compared with $3285 for the triaxial system.

Table 2

Procedure details

Statistical analysis showed that the time from guide-catheter run to PED deployment was significantly shorter in the biaxial group (24.0±18.73 min vs 38.4±31.1 min, P=0.0005). Fluoroscopy time was also significantly shorter in the biaxial group (28.8±23.0 min vs 50.3±27.1 min, P=0.001). This finding was consistent with reduced radiation exposure to the skin in the biaxial group compared with the triaxial group (1243.7±808.2 mGy vs 2074.6±1505.6 mGy, P=0.003). However, there was no statistically significant difference in complication rates and mRS scores at 30 days. One patient death occurred in the biaxial group. The patient had presented with Hunt and Hess grade 4 subarachnoid hemorrhage due to a ruptured blister supraclinoid dorsal carotid wall aneurysm. The aneurysm was the only one in our cohort that was treated with a PED acutely in the setting of subarachnoid hemorrhage because of the morphology and location of the aneurysm. The patient’s neurological status did not improve after PED deployment. The patient developed severe vasospasm of the middle cerebral artery and continued to decline in neurological status. Care was discontinued according to the family’s wishes on the basis of the patient’s living will. The outcomes of the study cohort are summarized in table 3.

Table 3

Comparison of outcomes associated with biaxial and triaxial systems

On multivariate logistic regression, including variables such as aneurysm location, aneurysm size, type of microcatheter, catheter system, age, and sex, the use of a biaxial system was found to be an independent determinant of reduced procedure and fluoroscopy times, with odds ratios of 69.52 (95% CI 50.27 to 88.77) and 35.53 (20.20 to 50.87), P<0.001, respectively. The results of the multivariate analyses are shown in online supplementary tables 1 and 2.


Our results show that biaxial access for the deployment of a PED to treat intracranial aneurysms allows for more time-efficient delivery with respect to total fluoroscopy time and interval from initial guide catheter injection to PED deployment. This efficiency occurred without a significant increase in complications of any kind, and specifically, thromboembolic complications. Although the entire cost of each case was not calculated to determine if there was significant cost effectiveness in using biaxial access, the cost differential between the two techniques was $1495. This is based on the difference in unit cost of an intermediate catheter and a 0.088 inch guide catheter versus a 0.071 inch guide catheter.

In three instances (6.1%) a biaxial catheter system was unable to provide the necessary support for successful PED deployment. These cases were included in our analysis to demonstrate the increased procedure time for conversion from a biaxial to a triaxial catheter system.

Initially, biaxial access was the standard for endovascular neurointerventions.2 Some interventionalists felt this provided inadequate haptic feedback; thus, large, supportive catheters were designed, resulting in the triaxial system using an intermediate catheter.5 Several series in the literature have demonstrated the safety and effectiveness of the triaxial system with the use of a Navien 0.058 inch catheter.5 6 Some authors have even devised a more complex system such as a pentaxial system.9 However, as guide catheter technology has improved, leading to better stability and ease of safe navigation higher into the internal carotid system, the biaxial system has again demonstrated its usefulness in the neuroendovascular literature.7 8 A comparison study analyzing the differences between the two systems at high-volume neuroendovascular practices has not yet been carried out.

The argument for the use of a triaxial system is to provide support to the microcatheter delivering the PED more distally, specifically by advancing the intermediate catheter into the petrocavernous carotid artery or possibly further. One disadvantage discussed in the literature is that there may be an increased risk of thromboembolic complications as a result of increased flow stasis from a larger access triaxial system.4 Alternatively, the biaxial system is believed to provide a more efficient method for accessing the parent vessel and enough support to deliver a PED device in most locations. The criticism of the biaxial system is that it does not work well in tortuous arch, cervical, or distal intracranial anatomy. The more tortuosity, the more support a system needs to be able to effectively and accurately deliver a PED. In 4 of 49 cases (8.2%), a V18 support wire (Boston Scientific) was used to increase the proximal rigidity and support of the guide catheter to allow safe and effective delivery of a PED through a biaxial system. Increasing the base rigidity of the guide catheter is one means of enhancing the flexibility and versatility of biaxial systems. In some circumstances, conversion to a triaxial system is necessary, as was seen in 3 (6.1%) of 49 cases in our biaxial group. This conversion between systems does increase patient exposure to radiation, manipulation in the arch and cervical vessels, cost from additional devices opened, and procedure time.

Pipeline embolization has become an established method for the treatment of intracranial aneurysms and one advantage that it affords over traditional methods, such as coiling or stent-coiling, is the reduced amount of fluoroscopy time required to treat an aneurysm, thus benefiting both the patient and the interventionalist.2 Our results disclosed mean total fluoroscopy times of 28.8±23.0 min for biaxial cases and 50.3±27.1 min for triaxial cases, representing a statistically significant difference (P<0.001). Other authors, such as Colby et al, have found similar time intervals using a triaxial system and reported a mean fluoroscopy time of 54.6±7.8 min with the use of a triaxial system.10 Another study reported a mean time of 53.3±23 min for the use of a triaxial system for PED deployment in paraclinoid aneurysms.11 The series on the use of the biaxial system by Patel et al did not report procedure time.8

Radiation exposure in our patients using the triaxial system was also less than that reported in the study by Colby et al (ie, 2074.6±1505.6 mGy vs 2680±358 mGy).10 The radiation exposure with the use of the biaxial system (ie, 1243.7±808.2 mGy in our series) was significantly less than with the triaxial group (P value=0.003).

In the present series, the rate of thromboembolic complications in the biaxial group was 2.1%, compared with 6.1% in the triaxial group, which was not statistically significant. Reports in the literature of the rate of thromboembolic complications after PED have been variable. Patel et al reported a thromboembolic complication rate of 3.8% using a biaxial system.8 Chitale et al reported a rate of thromboembolic complications (combined symptomatic and asymptomatic) of >11% with a triaxial system.12

The most commonly used guide catheter in our series was the Envoy DA XB (table 2) (used in 67.4% in the biaxial group), although we also used Benchmark (Penumbra) (4.1%), and Envoy XB (Codman) (22.4%) catheters. The Navien 0.058 inch catheter was used in all of our triaxial cases and has been used in previous studies with promising results.5 13 The average cost of a biaxial system was $1790 compared with $3285 for the triaxial system. The expense was mainly due to the high price of the intermediate catheter. In an era where cost is a major discussion point when considering aneurysm treatment options,14 catheter cost, along with the reduction of procedure time and fluoroscopy time, can significantly affect the overall treatment cost.

The choice of catheters is variable and depends on personal experience and preference. Patel et al used Benchmark and Marksman catheters.8 In a technical report, Al-Mufti et al used an Envoy DA XB catheter (Codman) with a Marksman catheter.7 We used several different catheters in the biaxial group in our series (table 2). The triaxial system described in the literature consists of a 0.087 inch inner diameter Shuttle sheath (Cook Medical, Bloomington, Indiana, USA) or a 0.088 inch inner diameter Neuron MAX guide catheter, a Navien 0.058 inch inner diameter distal intracranial catheter, and either a 0.027 inch inner diameter Marksman catheter or a 0.027 inch inner diameter Excelsior XT-27 catheter.4 5 The choice of catheters in our triaxial group was similar to that described in the literature (table 2).

It is important to note that there are significant performance differences with 6 F guide catheters compared with a few years ago (Envoy XB, DePuy Synthes) that allow reliable delivery of 6 F guide catheters into the petrocavernous carotid artery (Envoy DA, Benchmark). These improvements, along with newer microcatheters such as the Phenom 027 (Medtronic), have significantly improved the reliability and support during PED deployment, thus improving biaxial performance.

A key feature that appears to affect performance is vascular tortuosity from the arch to the aneurysmal segment. It is imperative that proximal anatomy is evaluated before the procedure, ideally using non-invasive means such as magnetic resonance angiography and computed tomographic angiography to design a successful delivery system. In our series, there was a small 6.1% rate of biaxial failure requiring triaxial substitution, which could be anticipated on preoperative review of arch and cervical anatomy. Nevertheless, for the overwhelming majority of cases (93.9%), triaxial delivery cost more, took longer with greater radiation exposure for patient and neurointerventionalist, and provided no advantage in clinical or angiographic outcomes.

Our study has some limitations. Data were prospectively collected but retrospectively reviewed, and the selection of devices was determined by the preferences of the senior authors. Therefore, we could not objectively document and compare the anatomy of the aortic arch, which is an important variable affecting arterial access. Another limitation is that the cost comparison is empirical. The cost effect of the catheter system on the overall admission cost was not estimated. Although 94% of the patients did benefit from the successful use of a biaxial catheter system alone, the empirical cost analysis was not applicable to 6% of the cases in which the biaxial system was exchanged for a triaxial system, or a V18 wire was used for additional support. Moreover, case selection was based on the personal preferences of the operators. Despite these limitations, there are benefits to both approaches. The benefits of the biaxial approach include less radiation and a decrease in procedure time. The triaxial system allows for more operator control during PED deployment by creating a more stable platform through intermediate catheters in close proximity to the stent-deployment zone. Because neurointerventionalists more commonly use a triaxial system for catheter delivery, the decrease in procedure time and radiation would be more evident when a provider is accustomed to using the biaxial approach.


In most cases with favorable anatomy, a biaxial system can be a safe and effective means of deploying a PED and provide significant value in faster procedure times and lower patient radiation dosage, all with an incidence of <7% of prolonged procedure time due to intraprocedural change of delivery system. We believe that use of the biaxial system can considerably reduce costs by decreasing procedure time and avoiding the expense of an extra catheter in those patients with severe vascular tortuosity.


We thank Paul Dressel BFA for preparation of the illustrations, Jiefei Wang MA for assistance with statistical analysis, and W Fawn Dorr and Debra J Zimmer for editorial assistance.


Supplementary materials

  • Supplementary Data

    This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.


  • Presented at Digital poster presentation, Congress of Neurological Surgeons Annual Meeting, Boston, Massachusetts USA, October 7-11, 2017.

  • Contributors Conception and design: EIL, HJS, HS, MW; data acquisition: all authors; data analysis and interpretation: MW, KV; drafting the manuscript: MW, KV; critically revising the manuscript: all authors; final approval of the manuscript: all authors.

  • 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.

  • Competing interests AHS: financial interest/investor/stock options/ownership: Amnis Therapeutics, Apama Medical, Blink TBI Inc., Buffalo Technology Partners Inc., Cardinal Consultants, Cerebrotech Medical Systems, Inc. Cognition Medical, Endostream Medical Ltd., Imperative Care, International Medical Distribution Partners, Neurovascular Diagnostics Inc., Q’Apel Medical Inc, Rebound Therapeutics Corp., Rist Neurovascular Inc., Serenity Medical Inc., Silk Road Medical, StimMed, Synchron, Three Rivers Medical Inc., Viseon Spine Inc; consultant/advisory board: Amnis Therapeutics, Boston Scientific, Canon Medical Systems USA Inc., Cerebrotech Medical Systems Inc., Cerenovus, Corindus Inc., Endostream Medical Ltd., Guidepoint Global Consulting, Imperative Care, Integra LifeSciences Corp., Medtronic, MicroVention, Northwest University–DSMB Chair for HEAT Trial, Penumbra, Q’Apel Medical Inc., Rapid Medical, Rebound Therapeutics Corp., Serenity Medical Inc., Silk Road Medical, StimMed, Stryker, Three Rivers Medical, Inc., VasSol, W.L. Gore & Associates; principal investigator/steering comment of the following trials: Cerenovus NAPA and ARISE II; Medtronic SWIFT PRIME and SWIFT DIRECT; MicroVention FRED & CONFIDENCE; MUSC POSITIVE; and Penumbra 3D Separator, COMPASS, and INVEST.EIL; shareholder/ownership interests: NeXtGen Biologics, RAPID Medical, Claret Medical, Cognition Medical, Imperative Care, Rebound Therapeutics, StimMed, Three Rivers Medical; National Principal Investigator/Steering Committees: Medtronic, SWIFT Prime and SWIFT Direct Trials; Honoraria: Medtronic;Consultant: Claret Medical, GLG Consulting, Guidepoint Global, Imperative Care, Medtronic, Rebound, StimMed; Advisory Board: Stryker (AIS Clinical), NeXtGen Biologics, MEDX, Cognition Medical, Endostream Medical; Site Principal Investigator: CONFIDENCE study (MicroVention), STRATIS Study—Sub I (Medtronic).

  • Patient consent for publication Not required.

  • Ethics approval This study was approved by the University at Buffalo Institutional Review Board (IRB ID: 030- 578913).

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Author note Importance of this work and its contribution to existing literature: (1) Deployment of Pipeline embolization devices (Medtronic, Dublin, Ireland) can be achieved with a biaxial or a triaxial system of catheters. (2) In this study, we share our experience with the use of these two catheter delivery systems for the deployment of Pipeline devices for intracranial aneurysm treatment. (3) To our knowledge, this is the first study to highlight the differences in procedure time, radiation exposure, and potential cost associated with the use of two different catheter systems.