Introduction
Near or complete occlusion of the carotid artery is often due to severe clot and plaque buildup and is associated with an elevated risk of spontaneous distal embolization, potentially leading to a tandem stroke [1–3]. A tandem cervical internal carotid artery (ICA) and intracranial vessel occlusion is the epitome of a symptomatic carotid stenosis. Emergent carotid angioplasty and stenting (eCAS) is recommended alongside mechanical thrombectomy for tandem strokes [4]. Current efforts are geared towards optimizing procedural anterograde or retrograde approaches to tandem occlusions, with one focus being on better controlling distal embolization of plaque and clot distally during the CAS portion of the procedure. The advent of second-generation carotid stents featuring novel dual-layer designs with telescoped stent and micromesh components aims to prevent plaque or thrombus protrusion through the stent tines causing distal embolization during CAS for carotid thrombostenosis. Tekieli et al. reported their multi-center experience with the CGuard Embolic Prevention System (EPS; InspireMD Inc, Tel Aviv, Israel) in the management of acute carotid thrombostenosis. They observed zero ipsilateral strokes stemming from the treated carotid artery and a 92.2% rate of stent patency at 90 days [5]. Interestingly, their cohort included 52% tandem strokes, of which a majority of 69.2% were treated using a retrograde approach.
Although numerous debates have emerged regarding the superiority of an anterograde or retrograde approach to tandem strokes, evidence indicates that the two modalities perform equally in achieving a modified Rankin Scale (mRS) score of 0–2 at 90 days, as well as in rates of symptomatic intracranial hemorrhage (sICH), successful recanalization, first-pass effect, and mortality at 90 days [6]. However, the anterograde approach is associated with significant, yet obvious, longer recanalization times. It is important to note that the evidence supporting these observations is gathered from a multitude of approaches guided by operator preference and patient-anatomy specific scenarios, making it challenging to define a singular “anterograde approach.” Nevertheless, the underlying principles are guided by the goals of achieving adequate flow reversal, preventing blind maneuvering into the intracranial circulation during tandem strokectomies, and characterizing the carotid pathology before intracranial manipulation, which contribute to a protocolized, stepwise approach to prevent distal embolization in tandem strokes.
The Buffalo Protocol
We have developed a stepwise anterograde approach towards tandem strokes, which is detailed here. An 8-French (8F) sheath is inserted into the common femoral artery to establish arterial access. An 8F balloon guide catheter (BGC; e.g., Walrus, Q’Apel Medical, Fremont, CA, USA) is advanced into the common carotid artery (CCA) using a 5F Simmons Select catheter (Penumbra, Alameda, CA, USA) and a 0.035-inch Exchange or Advantage Glidewire (Terumo Interventional, Somerset, NJ, USA) for guidance. The preference for BGC over conventional guide catheters is due to the demonstrated reductions in procedural times, increased first-pass effect rates, and lower rates of periprocedural symptomatic hemorrhagic conversion in patients with tandem occlusions [7]. Additionally, the use of a BGC is associated with greater improvements in National Institutes of Health Stroke Scale scores and higher odds of achieving a 90-day mRS score of 0–2 [7]. These benefits can be attributed to the more effective flow reversal, which helps prevent distal embolization of both macro- and micro thrombi into the intracranial vasculature, thereby enhancing neuroprotection [8].
With the BGC inflated, the carotid lesion is crossed using a carotid wire (e.g., Spartacore Guide Wire, Abbott Vascular, Santa Clara, CA, USA; or Abbott Hi-Torque Command Workhorse, Abbott Vascular, Santa Clara, CA, USA) into the distal internal carotid artery. An angioplasty balloon (e.g., AVIATOR Plus PTA Dilatation Catheter, Cordis, Miami Lakes, FL, USA) is then advanced across the thrombosed or stenotic segment and inflated to nominal pressure for 20–30 s. This step helps delineate the site of the carotid occlusion and lesion based on balloon dilatation. Following this, aspiration is performed through the BGC to remove any debris while the BGC remains inflated. A carotid stent (e.g., CGuard EPS) is then navigated across the stenotic or thrombosed area and deployed. After stent deployment, a second aspiration is conducted to clear any remaining debris. Intermittent angiography is performed to assess the adequacy of stent deployment, with post-dilation angioplasty carried out as necessary to optimize stent expansion and apposition. After a third round of aspiration, the BGC is deflated and carefully navigated across the newly placed stent toward the higher intracranial vessels. Based on the angiographic findings, mechanical thrombectomy is planned accordingly.
Rationale
Any manipulation of the carotid lesion carries the risk of distal embolization. The BGC is kept inflated throughout the eCAS procedure, effectively eliminating forward flow. When combined with repeated flow reversal at each stage, this technique effectively prevents distal embolic showering into the intracranial space.
Engaging the clot directly in the retrograde approach raises two key concerns: 1) It may inadvertently convert an isolated carotid thrombostenosis into a tandem stroke, necessitating additional intervention. This not only prolongs the procedure but also increases the risk of adverse neurological and functional outcomes, in addition to elevating operative and hospital costs for the patient. 2) It can cause damage to catheters, leading to their suboptimal performance and inefficient recanalization, especially if the carotid pathology is calcified.
The added benefit of the Buffalo Protocol is that upfront balloon angioplasty under obstructed forward flow can reveal the exact location of the severe stenosis or near occlusion. This facilitates early decision-making regarding the need for eCAS.
The future of CGuard EPS in tandem strokes
The CGuard EPS features a dual-layer nitinol mesh, with the self-expandable open-cell stent that exerts a radial outward pressure on the outer MicroNET cover ensuring the thorough apposition of the mesh against the vessel wall [9, 10]. Additionally, the tight MicroNET cover across the stent prevents “cheese-grating” of acute and chronic plaque, thereby reducing the risk of additional emboli and stroke in the intracranial space. Together, these features of the CGuard result in effective containment of the plaque, preventing inadvertent intraprocedural embolization and reducing the risk of tandem conversion. Additionally, they help prevent postprocedural embolization, thereby mitigating the risk of recurrent ipsilateral ischemic strokes [11]. Anterograde approaches have historically been described in the context of first-generation stents, which are more susceptible to periprocedural and follow-up strokes. This has created an opportunity for the development and use of second-generation stents, such as the CGuard, the Roadsaver Carotid Stent System (Terumo Corp, Tokyo, Japan), and the Gore Carotid Stent (W.L. Gore & Associates, Flagstaff, Arizona, USA) in the tandem stroke realm [11].
Conflict of interest
JL, VJ, TAS – None. AHS – Consulting fees: Amnis Therapeutics, Apellis Pharmaceuticals, Inc., Boston Scientific, Canon Medical Systems USA, Inc., Cardinal Health 200, LLC, Cerebrotech Medical Systems, Inc., Cerenovus, Cerevatech Medical, Inc., Cordis, Corindus, Inc., Endostream Medical, Ltd, Imperative Care, Integra, IRRAS AB, Medtronic, MicroVention, Minnetronix Neuro, Inc., Penumbra, Q’Apel Medical, Inc., Rapid Medical, Serenity Medical, Inc., Silk Road Medical, StimMed, LLC, Stryker Neurovascular, Three Rivers Medical, Inc., VasSol, Viz.ai, Inc., W.L. Gore & Associates. Leadership or fiduciary role in other board, society, committee or advocacy group: Secretary of the Board of the Society of NeuroInterventional Surgery, Chair of the Cerebrovascular Section of the AANS/CNS. Stock or stock options: Adona Medical, Inc., Amnis Therapeutics, Bend IT Technologies, Ltd., BlinkTBI, Inc, Buffalo Technology Partners, Inc., Cardinal Consultants, LLC, Cerebrotech Medical Systems, Inc, Cerevatech Medical, Inc., Cognition Medical, CVAID Ltd., E8, Inc., Endostream Medical, Ltd, Imperative Care, Inc., Instylla, Inc., International Medical Distribution Partners, Launch NY, Inc., NeuroRadial Technologies, Inc., Neurotechnology Investors, Neurovascular Diagnostics, Inc., PerFlow Medical, Ltd., Q’Apel Medical, Inc., QAS.ai, Inc., Radical Catheter Technologies, Inc., Rebound Therapeutics Corp. (Purchased 2019 by Integra Lifesciences, Corp), Rist Neurovascular, Inc. (Purchased 2020 by Medtronic), Sense Diagnostics, Inc., Serenity Medical, Inc., Silk Road Medical, Adona Medical, Inc., Amnis Therapeutics, Bend IT Technologies, Ltd., BlinkTBI, Inc, Buffalo Technology Partners, Inc., Cardinal Consultants, LLC, Cerebrotech Medical Systems, Inc, Cerevatech Medical, Inc., Cognition Medical, CVAID Ltd., E8, Inc., Endostream Medical, Ltd, Imperative Care, Inc., Instylla, Inc., International Medical Distribution Partners, Launch NY, Inc., NeuroRadial Technologies, Inc., Neurotechnology Investors, Neurovascular Diagnostics, Inc., PerFlow Medical, Ltd., Q’Apel Medical, Inc., QAS.ai, Inc., Radical Catheter Technologies, Inc., Rebound Therapeutics Corp. (Purchased 2019 by Integra Lifesciences, Corp), Rist Neurovascular, Inc. (Purchased 2020 by Medtronic), Sense Diagnostics, Inc., Serenity Medical, Inc., Silk Road Medical, SongBird Therapy, Spinnaker Medical, Inc., StimMed, LLC, Synchron, Inc., Three Rivers Medical, Inc., Truvic Medical, Inc., Tulavi Therapeutics, Inc., Vastrax, LLC, VICIS, Inc., Viseon, Inc. Other financial or non-financial interests: National PI/Steering Committees: Cerenovus EXCELLENT and ARISE II Trial; Medtronic SWIFT PRIME, VANTAGE, EMBOLISE and SWIFT DIRECT Trials; MicroVention FRED Trial & CONFIDENCE Study; MUSC POSITIVE Trial; Penumbra 3D Separator Trial, COMPASS Trial, INVEST Trial, MIVI neuroscience EVAQ Trial; Rapid Medical SUCCESS Trial; InspireMD C-GUARDIANS IDE Pivotal Trial.
