INTRODUCTION
In carotid artery stenting (CAS), precise guidance of the wire through the lesion and into the distal vessel is crucial. However, there are instances where wiring becomes challenging due to severe tortuosity or heavy calcification [1,2], which can lead to treatment failure. In such cases, individualized solutions are necessary.
In our case of CAS for carotid artery stenosis with severe tortuosity, the use of a steerable microcatheter (SM) facilitated successful wiring to the target vessel. The SM (Leonis Mova®; Sumitomo Bakelite Co., Ltd.), introduced in 2014, features a remote-controlled flexible tip and 2 diagonally placed steering wires within the catheter wall, extending from the handle to the distal tip. By turning the steering dial, tension is applied to either wire, allowing precise manipulation of the tip direction. Once the desired direction is achieved, the steering dial lock secures the position. The SM is adopted for neuroendovascular treatments, including aneurysms and dural arteriovenous fistulas (dAVFs) [3-7]. This report is to document the use of an SM for CAS.
CASE REPORT
A 67-year-old male with a history of hypertension, diabetes mellitus, and chronic total occlusion of the right coronary artery presented with transient lower extremity weakness lasting from several minutes to 1 hour. Cerebral magnetic resonance imaging revealed multiple bilateral cerebral infarcts and bilateral internal carotid artery (ICA) stenosis. Consequently, dual antiplatelet therapy was initiated with aspirin (100 mg) and clopidogrel (75 mg). Follow-up cerebral angiography demonstrated pseudo-occlusion of the right ICA. The left carotid artery exhibited marked tortuosity from the common carotid artery (CCA) to the ICA, with calcified lesions protruding from the posterior wall to the ventral aspect. This atherosclerotic remodeling resulted in an ICA-CCA steep angulation. Due to coronary artery disease, CAS was planned for both carotid artery stenosis, rather than carotid endarterectomy. CAS was initially performed on the symptomatic right ICA with pseudo-occlusion. Given the potential need for future intervention on the chronically occluded right coronary artery, the decision was made to proceed with CAS for the left carotid artery stenosis as well.
Under local anesthesia and following systemic heparinization, an 8 Fr guiding catheter (Branchor XB, 90 cm; Asahi Intecc Co., Ltd.) was advanced from the right femoral artery into the left CCA. Diagnostic angiography revealed 74% stenosis of the proximal ICA according to North American Symptomatic Carotid Endarterectomy Trial (NASCET) criteria, with a lesion length of 20 mm. The heavily calcified plaque was located at the carotid bulb, extending from the posterior wall to the ventral aspect, causing stenosis in both the ICA and the CCA (Fig. 1A, B). Therefore, the pathway from the CCA to the ICA exhibited significant tortuosity, nearly perpendicular, which posed challenges in ICA selection and device delivery. A Leonis Mova® Selective microcatheter 125 cm (Sumitomo Bakelite Co., Ltd.), in conjunction with a CHIKAI 14 guidewire 200 cm (Asahi Intecc Co., Ltd.), was navigated to the distal external carotid artery (ECA). The microcatheter tip was precisely bent towards the ICA, and the angle was fixed using the locking mechanism. By pulling out the microwire, the microcatheter tip engaged the ICA origin (Fig. 1C, D). The microwire was then advanced distally through the fixed Leonis Mova® microcatheter (Fig. 1E). An EXTENSION NV 165 cm (Asahi Intecc Co., Ltd.) was connected to the CHIKAI 14, and the Leonis Mova® was exchanged for a Spider FXTM 6 mm embolic protection device (EPD) (Medtronic), which was deployed in the cervical ICA. Following deployment of the Spider FXTM, a 4×20 mm balloon (KANEKA) and a 6×30 mm balloon (KANEKA) were used for angioplasty of the ICA and CCA at the level of the stenosis prior to the deployment of an 8×29 mm carotid WALLSTENTTM (Boston Scientific) across the lesion. A 6×20 mm balloon (KANEKA) was then used for post-stenting angioplasty. Angiography confirmed improvement in the diameter of the carotid bifurcation with proper stent placement, spanning from the distal CCA to the proximal cervical ICA, effectively straightening the tortuosity of the CCA-ICA (Fig. 1F).
The postoperative course was uneventful, and post-procedural carotid Doppler ultrasonography revealed minimal to mild residual stenosis of the left ICA with adequate stent patency. The patient was maintained on aspirin and clopidogrel for 3 months. At the 3-month follow-up, both stents were found to be patent, so the treatment was reduced to clopidogrel alone.
DISCUSSION
The SM became available for use in the head and neck region in December 2022 and has since been utilized in various neuroendovascular treatments, as reported in several studies [4,5,8]. For instance, the SM has been used to select shunt points from the sinus during transvenous embolization for dAVFs and to access distal vessels during flow diverter placement in giant aneurysms without false intra-aneurysm canulation [3,6,7]. The advantages of this microcatheter include enhanced vessel selectivity due to its steerable tip and maintained tip shape through a fixation mechanism—capabilities not found in other devices [9]. The SM is particularly beneficial for navigating vessels with an acute angular origin or selecting small vessels from a larger-diameter vessel. Its support also ensures stable device delivery. The disadvantage is that the part about 10 mm from the tip bends the most, making it difficult to bend the tip to a small radius or into a complex shape such as an S-shape. This article is the first to report the utilization of the vessel selectivity and tip shape retention of the SM in CAS for carotid artery stenosis with severe tortuosity.
Previous studies have reported that a tortuous approach route significantly complicates device manipulation [10-12]. Naggara et al. [2] highlighted that ICA-CCA angulations greater than 60° increase the risk of stroke and death. However, the use of EPDs can mitigate these risks [2]. In a typical CAS procedure, vessel selection and lesion crossing are often performed using device-integrated wires, such as the FilterWire EZTM (Boston Scientific). In cases of severe tortuosity, devices like the Spider FXTM with a Rapid Exchange System are often employed, as they allow the microwire to guide the initial approach. We believe that crossing a lesion before EPD deployment carries a high risk of plaque disruption and distal embolization. Prominent angulation of the ICA origin or stenosis in the CCA can limit wire manipulation and complicate successful wiring. As a result, such a situation can complicate distal device navigation and EPD deployment, leading to technical failure [10,13]. Achieving smooth lesion passage is crucial to carry out the treatment successfully.
In this case, a heavily calcified plaque extended into the CCA bifurcation, significantly limiting wire manipulation at the site of the CCA stenosis. Moreover, the protruding plaque exacerbated luminal tortuosity, resulting in a nearly perpendicular CCA-ICA angulation. Given these factors, we anticipated that the wire would likely deviate toward the ECA, complicating smooth selection and passage through the lesion (Fig. 2A). According to the NASCET criteria, the stenosis rate was 74%, but computed tomography angiography showed that the lumen wall was irregular due to calcified plaque. We thought that if the wire got stuck in the irregular plaque, the wiring and navigation would be restricted. In addition, due to the plaque protruding on the anterior wall of the CCA, the wire manipulation is restricted in the direction far from the ICA entrance, and it will become difficult to advance the wire into the ICA. It would have been relatively easy to navigate to the ICA side without the protruding plaque on the CCA. Therefore, we opted to use a SM to select the ICA origin, support wire manipulation, and successfully guide the wire distal to the lesion. In practice, before inserting the catheter, the tip was manipulated outside the vessel to check that the catheter was appropriately bent to accommodate the tortuosity of the vessel (Fig. 2B). The SM was initially guided into the ECA, where the tip was bent to the angle pre-simulated and locked into position (Fig. 2C). As the wire was pulled out, the tip engaged with the ICA origin (Fig. 2D). With the support of the SM, the wire was easily guided distal to the lesion in the ICA (Fig. 2E). This approach minimized the number of devices passing through the stenosis. Consequently, we anticipate that smooth wiring prior to deploying the distal protection device may reduce the risk of distal embolization.
In this case, with a severely calcified lesion accompanied by tortuosity, we selected a closed-cell stent due to concerns that the struts of an open-cell stent might protrude into the lumen and hinder device passage. The closed-cell stent has the advantage of straightening tortuous lesions and facilitating device navigation post-stenting. Although there was a risk of poor expansion and delayed shortening [14-16] if the stent failed to conform closely to the lesion, we were able to complete the procedure without major complications. Nevertheless, cases with severe tortuosity present a high risk of complications during CAS, and carotid endarterectomy should be considered whenever possible. In cases where CAS is preferred due to ischemic heart disease or systemic complications, the use of a SM may be a viable solution.
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