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Abstract
Background Stable access to target lesions is foundational to endovascular therapy, be it in hemorrhagic or ischemic disease. Continued evolution in access technology has resulted in next generation catheters that afford improved trackability and proximal support.
Objective Assess safety and patterns of use at two high volume centers, and conceptualize usage patterns.
Materials and methods A retrospective review of 608 cases in which a ‘next generation’ catheter was used during 2008–2010 at Cleveland Clinic (Cleveland, Ohio, USA) and throughout 2009–2010 at Emory University Hospital (Atlanta, Georgia, USA) was conducted, and the cases classified by indication. Catheter placement, distal most location, and related complications were recorded and experience summarized. We also reviewed the differences in the catheters and the rationale for catheter selection, as well as relative costs for each approach.
Results 311 Neuron 053, 166 Neuron 070, 36 distal access catheter (DAC) 3.9 F, 61 DAC 4.3 F, and 34 DAC 5.2 F catheters were deployed. Of these, 459 placements were in the anterior circulation, 130 in the posterior circulation, 11 in the external carotid artery, and eight were used intravenously. Complication rates were 9/131 (6.9%) for the DAC catheter group, 16/311 (5.1%) for the Neuron 053 group, and 14/166 (8.4%) for the Neuron 070 group (p=0.37, χ2 test).
Conclusions Next generation access catheters possess characteristics that blend qualities of traditional microcatheters and stiff guide catheters. There was no statistically significant difference in complication rates between the various catheter families in this small retrospective review, and the complication rates were similar to historical complication rates.
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Introduction
Stable access to target lesions is foundational to endovascular therapy, be it in hemorrhagic or ischemic disease states. Modern catheters afford improved trackability and support. From a neurointerventional perspective, earlier generations of access catheters can be divided into sheath, guide, and microcatheters. Blurring the line between the guide catheter and the microcatheter, modern catheters are of an intermediate size, and afford improved stability at positions more distal than previously feasible using earlier generation guide catheters, and can be conceptualized as flexible tip guides as well as intermediate catheters.
The Neuron guide catheter family (Penumbra Inc, Alameda, California, USA) can be considered a modern flexible tip guide catheter, and the Concentric Outreach distal access catheter (DAC; Stryker, Kalamazoo, Michigan, USA) and Navien catheters (Covidien, Irvine, California, USA) may be considered intermediate catheters. The Penumbra Neuron family includes the 0.053 inch and 0.070 inch guide catheters, which have high rigidity proximal portions designed to maintain straightness through the aorta and proximal great vessels while having a flexible distal portion and staged transition zones that allow for more distal placement of the catheter tip. The DAC catheter family was initially designed for the purposes of buttressing access for the Merci thrombectomy device,1–3 and affords stable access to the target vessel modulating the forces at play within the thrombectomy device complex. Both Navien and DAC catheters do not have markedly stiffer proximal shafts.
These devices possess overlapping characteristics, allowing operators to achieve a more stable proximal access complex that makes control of the innermost treatment catheter more predictable, reducing the amount of play when advancing or withdrawing the catheter, as we have described in a previous report.4 The coaxial system used with guide, intermediate catheter, and microcatheter is compared, with an example of a flexible tip guide with microcatheter, in figure 1.
Artist's representation of the essential difference between traditional guide catheters, a flexible tip guide device versus a multi-axial platform with ‘intermediate catheter’ device.
In this report, we review the aggregate case volume at two high volume centers to assess the types of cases in which the catheters were used, the complication rates and types, as well as the distal most placement in each case, as well as propose a taxonomic system of current generation catheters. The Navien family of catheters was not commercially available during the study time period.
Methods
A retrospective review of all cases in which an intermediate catheter or flexible guide was used during 2008–2010 at Cleveland Clinic (Cleveland, Ohio, USA) and throughout 2010 at Emory University Hospital (Atlanta, Georgia, USA) was conducted, and the cases classified by indication. Catheter placement, distal most location, and related complications were recorded and experience summarized.
Results
A total of 608 between September 2007 and October 2010 using a DAC family of catheters (Concentric Medical, Mountain View, California, USA) or a Neuron family of catheters (Penumbra Inc) were identified. Table 1 summarizes the clinical scenarios in which the catheters were used. Table 2 summarizes the locations and distal most placement of the catheter as well as the types of cases. Table 3 summarizes the complications for each group of catheters. Table 4 summarizes relative costs of the basic catheter complexes commonly used at costs available at the Cleveland Clinic during the time of manuscript preparation. Table 5 describes the complication rates by type for the catheters studied.
Clinical scenarios
Distal most placement
Complication rates
Relative costs
Complications
Discussion
Although much of the attention to neuroendovascular therapy is given towards therapeutic devices, including coils, stents, or thrombectomy systems, delivery of the devices is an integral part of safe, efficient, and effective endovascular therapy. In particular, treatment of ischemic lesions often occurs in patients with risk factors for atherosclerotic disease and cardiovascular disease, such as hypertension, which can be associated with tortuous difficult aortic and supra-aortic vascular anatomy.5 In the setting of acute stroke, achieving stable access efficiently is of paramount importance as expediency is thought to be associated with better outcome.6 ,7 Improved distal support may also be useful for intracranial stenting4 ,8 ,9 and ethyl vinyl alcohol embolization.10 ,11
The first of these catheters to be introduced was the Penumbra Neuron family of catheters, starting with the 053 inner luminal diameter, followed by the 070,12–14 falling into the flexible tip guide taxonomy. The DAC family was initially introduced as an adjunct for use with the Merci retrievers1–3 but some authors have found utility in a wider range of neurovascular applications.4 ,10 ,15
The catheters reviewed in this series purport to improve access and access stability during interventional procedures and, in some cases, may allow for stable access in anatomy hereto inaccessible from groin access. Individual user habits will of course dictate the style of utilization. Modern catheter design tends to endeavor to preserve inner diameter while lessening outer diameter, and maintaining outward radial strength, such as seen in the Reflex 072 intermediate catheter (Reverse Medical, Irvine, California, USA). The preservation of inner diameter may help obviate the need for thick large catheters, sometimes needed to deliver multiple microcatheters simultaneously.16
The integration of multi-axial catheter techniques,17 using perhaps a guide or guide sheath in conjunction with intermediate catheters and microcatheters, requires keeping track of more flush lines and more catheters in the procedure field. However, despite the increased complexity, the complication rates we observed were in the range of recently published trials, such as the HydroCoil Endovascular Aneurysm Occlusion and Packing Study (HELPS)18 ,19 and the International Subarachnoid Aneurysm Trial (ISAT) trial,20 and were felt to be related to the complexity of the cases themselves, rather than the access techniques employed.
Flexible tip guides versus multi-axial approaches
The two basic approaches to increasing distal stability using a next generation catheter is to use a flexible tip system, such as the Neuron family of catheters, or an intermediate diameter catheter, such as a DAC. The DAC comes in several diameters which a range of sizes which allow for greater distal trackability at the expense of luminal capacity, thus yielding catheters that may be conceptualized as a guide extension versus a microcatheter stiffener. These two divergent approaches (figure 1) yield different advantages. Flexible tip guide catheters, once advanced into the petrous or cavernous segments, can offer great stability with a large luminal capacity (figure 2). However, given the large cross sectional size, a size mismatch with the guidewire may yield a shelf that can catch on vessel ostia or atherosclerotic irregularities, thus retarding distal placement. Additionally, if the transition between the stiffer proximal segment and the flexible distal portion happens to lie at the genu between the aortic arch and the selected vessel, stability is compromised. This relates to the fixed relationship between segments of the catheter.
Schematic diagram showing the overall layout of multi-axial approaches.
In contrast, a true multi-axial approach allows the operator to dynamically change the transition between catheter components, potentially allowing for reduced step-offs between individual catheters, and allowing stepwise advancement of progressively stiffer components to ultimately afford distal stability. For example, accessing a difficult tortuous right vertebral artery can be approached in a staged fashion by placing the guide/guide sheath in the brachiocephalic artery, followed by selection of the subclavian with the microcatheter and wire, followed by advancement of the intermediate catheter into the subclavian. From there, stepwise advancement can proceed, advancing each component as needed.
This approach however involves a greater number of catheters with accompanying increasing complexity of lines as well as costs. With these approaches, as many as five components may be seen in the access complex: sheath, guide, intermediate catheter, microcatheter, and microwire. It is conceivable that some might attempt a secondary intermediate catheter between the guide and the next smallest catheter, yielding a total of six components. Table 6 provides an ad hoc taxonomy for catheters ranging from the sheath to the microcatheter.
An interim taxonomy
Improved microcatheter control
There is a closer size match between the lumen of the intermediate catheter with the microcatheter, rather than within the vessel—this closer match reduces the freedom with which the inner catheter can buckle and create resistance. Typically, advancing a microcatheter requires that the microcatheter approximate the outer curvatures of the vessel before progressing forward. With an intermediate catheter constraining outward movement of the microcatheter, there is less redundancy, resulting in greater correlation to movement at the hub and movement within the patient. Indeed, control of microcatheter movement in conjunction with distally placed intermediate catheters can be exquisite (figure 3).
Anterioposterior angiography during a coil embolization of a basilar terminus aneurysm. The distal tip of the Neuron 053 is placed at the vertebrobasilar confluence (white arrow) and the proximal marker of the microcatheter is visible (black arrow) in the proximal basilar. The system affords exquisite control and tactile feedback during coil embolization.
Typically, the intermediate catheters assume a course closer to the inner curvature of the vessels. This results in less curvature through which delivery wires and devices must bend before reaching the target. Part of perceived resistance results from delivery wire resistance to bending.
Stable access for repeated microcatheter deployment
Stable distal access through any of the next generation devices may allow the operator to keep the tip of the flexible tip guide or the intermediate catheter on screen while magnified, while traversing the anatomy to the target vessel, which may be of use during access to a clot with thrombectomy devices, or if accessing an arteriovenous malformation.7 ,10
Angiography
Angiography can be performed with intermediate catheters in two fashions: directly through the intermediate catheter without an internal coaxial component or through the catheter while an internal catheter is present. In the first case, it should be noted that increased lumen distally afforded by these devices can result in better opacification of vascular lesions. Figure 4A shows proximal angiography of a slow flow vertebral artery to venous plexus shunt. Figure 4B shows improved vascular detail once an intermediate catheter is placed directly into the lesion, without an internal coaxial catheter.
(A) Catheter angiography in the left vertebral artery through a 5 F catheter demonstrates a vertebral artery–venous plexus shunt, without clear visualization of the drainage pathways. (B) Injection through a 043 distal access catheter (arrow) into the venous pouch reveals drainage within the spinal canal and in the venous plexus in the posterior soft tissues of the neck.
When injecting with an internal coaxial component in place, the reduced residual lumen between two closely sized matched catheters may impede contrast injections through either the guide or the intermediate catheter. This is related to increased resistance of the flow between two coaxial catheters. Flow resistance is proportional to the pressure differential required for a volumetric flow rate,
As a first order approximation, the hydraulic diameter,
where A is the cross sectional flow area and P is the wetted perimeter, can be used to approximate the flow resistance through
For coaxial catheters, the cross sectional area is smaller and the perimeter longer compared with a single catheter of comparable outer diameter and therefore the equivalent hydraulic diameter is smaller and flow resistance higher for coaxial catheters. Thus to obtain comparable flow distally, in light of the increased resistance to flow given the effectively reduced luminal diameter (which is raised to the fourth power), more pressure must be exerted at the syringe, which can be produced via a smaller plunger. Using 5 mL, 3 mL, or 1 mL syringes allows application of a higher pressure with the same amount of force due to the smaller cross sectional area of the plunger as pressure is equal to the force divided by the applied area
allowing for higher flow rates. Our group routinely uses 3 mL syringes, adjusting the size as necessary. However, given that injection through a DAC catheter typically allows for a very distal injection, a high volume of contrast is generally not necessary to obtain meaningful imaging.
Additionally, a theoretical concern is the increased possibility of injurious injections, as intermediate catheters allow for a higher flow of contrast, potentially increasing sheer forces at the catheter tip. Caution during distal angiography should be maintained.
Sizing
With the increasing number of intermediate catheters, mismatches in outer diameter to inner diameter, as well as length mismatches, may result in many discarded catheters. Familiarity with the lengths, and luminal diameter of the catheters, should reduce waste. Charts of compatibility are available from many of the manufacturers. Running out of microcatheter length due to selection of a long intermediate catheter can be vexing. Attention to rotational hemostatic valve length is also helpful.
Conclusions
While the majority of attention to neurointerventional devices relates to the actual therapeutic agent, advances in access device technology should not be ignored. Next generation catheters leverage advances in polymer and metal material sciences and construction techniques to improve flexibility, outward radial strength, and axial load bearing strength, while maximizing luminal diameter.
These next generation catheters can provide an added tool in the endovascular specialist's armamentarium. The ability to supply distal support and stability, more predictable microcatheter movement near the target lesion, and better control of the angulation of microcatheter deployment all provide potential benefits to endovascular therapeutic interventions.
In this series of 608 patients, we detected no iatrogenic complications directly attributable to the use of intermediate catheters. Familiarity with the nuances and having a grasp of a basic taxonomy of these devices is helpful towards efficient integration of these devices during interventional procedures. At present, these data show no statistical difference in the complication rates associated with performing procedures with these devices.
References
Footnotes
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Contributors FKH, manuscript preparation and editing. AJS, manuscript review and data collection. AMS, manuscript review and data collection. JY, fluid dynamic modeling. NO, statistical analysis and discussion. PAR, manuscript review. MSH, manuscript review. CMC, manuscript review, case performance, and discussion comments. JED, manuscript review, case performance, and discussion comments. FCT, data collection, manuscript review, conceptual discussion, and discussion comments.
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Competing interests The following authors have disclosures related to this work: JED, NFocus (stock) and Sequent Medical (stock options). FKH, Penumbra's Speaker's Bureau. PAR, Penumbra's Speaker's Bureau and is a stockholder.
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Ethics approval The study was approved by Cleveland Clinic and Emory University.
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Provenance and peer review Not commissioned; externally peer reviewed.