Intravascular lithotripsy-facilitated parallel-wire technique for severely calcified eccentric carotid artery stenosis: a technical case report

Introduction

Carotid artery stenosis with severe calcified lesions presents significant treatment challenges (1). While balloon angioplasty, including specialty balloons such as cutting and scoring balloons (2-4), can sometimes provide sufficient pre-dilation for stent deployment, the degree of luminal gain can often be limited, resulting in insufficient stent expansion and late restenosis (5-7). Particularly in eccentric calcified lesions, luminal gain with balloon angioplasty is achieved by stretching the non-calcified wall, leading to minimal calcium modification and an increased risk of dissection.

Intravascular lithotripsy (IVL) is a new technology that delivers pulsatile sonic pressure waves converted to mechanical energy to modify vascular calcium. These electrohydraulically generated sonic pressure waves pass through soft tissue but interact strongly with high-density calcium, producing significant shear stresses that can fracture calcium. Unlike focal, high-energy urological lithotripsy, the acoustic energy produced by IVL is specifically tuned for vascular treatments. IVL has been applied in peripheral and coronary artery diseases, effectively and safely modifying intimal and medial calcium without harming soft tissue, and has reported many good results (8-10). Recently, IVL has also been applied to severely calcified carotid arterial lesions, and good clinical results were achieved (11-19). Here, we report a case of carotid artery stenosis with severe calcification. Unlike previous reports where IVL was primarily used for luminal gain in concentric lesions, our case is unique in utilizing IVL specifically to modify the wiring axis in an ‘uncrossable’ eccentric lesion by facilitating a parallel-wire technique. We present this article in accordance with the CARE reporting checklist (available at https://jni.amegroups.com/article/view/10.21037/jni-26-0002/rc).

Case presentation

A 70-year-old female with a history of hypertension and chronic rheumatoid arthritis, on steroids and immunosuppressants, presented with sudden dysarthria and was admitted to our hospital. Magnetic resonance imaging (MRI) showed a cerebral infarction in the left insular cortex and severe stenosis of the left internal carotid artery (ICA). Her National Institutes of Health Stroke Scale was 1. The electrocardiogram revealed a sinus rhythm. She was hospitalized in our hospital. Dual antiplatelet therapy (oral aspirin 100 mg/day and clopidogrel 75 mg/day) was started immediately upon stroke onset. Her neurological symptoms resolved completely within three days of onset. Carotid endarterectomy (CEA) was considered high risk. Anatomically, the ICA coursed medially, positioning itself dorsolaterally to the pharynx [as seen at the C4 level on computed tomography angiography (CTA); Figure 1A]. This deep surgical field significantly increased the risk of injury to the superior laryngeal, vagus, and hypoglossal nerves. Twelve days after the initial onset, carotid artery stenting (CAS) was planned. Given the off-label status of IVL in the carotid artery, the procedure was performed following approval from our institutional review board (IRB) and with the Declaration of Helsinki and its subsequent amendments, and specific written informed consent regarding the off-label use was obtained from the patient.

Figure 1 Imaging findings and procedural steps of the intravascular lithotripsy-facilitated parallel-wire technique. (A) Initial CT angiography showed severe calcified stenosis in the left carotid artery. Left: axial image; right: sagittal image. The lesion was located posterior and lateral to the pharynx. (B) Pre-procedural angiographyshowed severe stenosis at the carotid bifurcation with severely calcified and eccentrically located plaque. The ICA (arrows) was collapsed. (C) X-ray during the application of a 3.0–12 mm Shockwave lithotripsy balloon to the eccentric lesion. The ICA was deviated anteriorly and medially. Arrow indicates the ICA. The CCA was occluded using a 9-F balloon guide catheter, and the external carotid artery was occluded with a balloon wire. (D) After intravascular lithotripsy, IVUS showed a minimum lumen diameter of less than 2 mm with eccentric high-density plaque. (E) A 0.018-inch wire was advanced through the center of the calcification via a parallel-wire technique while maintaining the previous wire in the true lumen. Arrow indicates ICA. (F) X-ray during 3–20 mm normal balloon dilation showed fractured calcified components. Arrow indicates the ICA. (G) IVUS after 5 mm balloon dilation showed a minimum lumen diameter of 2.1 mm × 3.0 mm with circumferential high-density plaque. (H) X-ray following placement of the carotid stent and subsequent 5 mm balloon dilation showed good expansion. (I) IVUS after post-dilatation revealed a minimum in-stent diameter of 2.8 mm × 5.2 mm with no in-stent plaque protrusion. (J) Final angiography indicated good stent dilation and antegrade ICA flow, which was still collapsed. Arrow indicates ICA. (B,C,E,F,H,J) The left image shows the anteroposterior view, and the right image shows the lateral view. CCA, common carotid artery; CT, computed tomography; ICA, internal carotid artery; IVUS, intravascular ultrasound.

The procedure was performed by two neurointerventional specialists with experience in over 1,000 and 300 CAS cases. Intraoperative systolic blood pressure was maintained between 100–120 mmHg, with ephedrine administered as needed for hypotension. On local anesthesia, a 9-F sheath and a 6-F sheath were deployed in the femoral artery and vein, respectively. Systemic anticoagulation was achieved by administering heparin to maintain an activated clotting time of at least 275 seconds. A temporary pacing catheter was deployed in the right ventricle. Pacing was performed in VVI mode, set at 50 beats/min. A 9-F Optimo balloon guiding catheter (BGC) (Tokai Medical Products, Aichi, Japan) was navigated to the left common carotid artery (CCA). The BGC is connected to a femoral venous sheath via an external filter, which collects particulate debris over 200 µm.

Pre-procedural angiography showed severe stenosis at the carotid bifurcation with severely calcified and eccentrically located plaque and a collapsed ICA (Figure 1B). The estimated NASCET stenosis was 95% due to the distal collapse of the ICA. A 0.014-inch balloon wire (Optimal wire, Tokai Medical Products) was navigated to the external carotid artery (ECA) to occlude it by inflating the device to 6 mm. Initially, a Gladius 14 wire (Asahi Intecc Co., Aichi, Japan), a peripheral vascular stiff guidewire, was used to attempt passage through the center of the calcification, but it could not pass through. A Synchro Select wire (Stryker, USA) was then passed through the curved stenotic lesion with intravascular ultrasound (IVUS; Eagle Eye Platinum ST, Philips Japan Ltd., Tokyo, Japan) support, but IVUS could not pass through. However, the true lumen that the wire passed through was located on the outer side of the eccentrically calcified plaque. Pre-dilatation with a SHIDEN 3.0–20 mm balloon (Kaneka Medics, Osaka, Japan) was performed at 6 atm. Despite this, IVUS passage was still not possible. Since the true lumen was eccentrically located, further dilation with a larger balloon catheter posed a high risk of vascular injury. Therefore, SHOCKWAVE C2 IVL (Shockwave Medical, Santa Clara, CA, USA) 3.0–12 mm was navigated to the lesion. The balloon was inflated to 4 atm and IVL was performed with 10 pulses per cycle of ultrasound energy (Video 1). Then, the inflation pressure was increased to the nominal pressure of 6 atm and the balloon was deflated. These steps were repeated every 10 pulses per cycle, and a total of 75 pulses of ultrasound energy were applied (Figure 1C). During the IVL procedure, temporary pacing was continuously maintained. After the IVL, the heart rate returned to its intrinsic rhythm. Following this, IVUS was able to pass, showing a minimum lumen diameter of less than 2 mm with eccentric high-density plaque (Figure 1D). As the passing site was not entirely covered by circumferential calcification, another axis was used to wire the center of the calcification.

Using the Prominent Raptor penetration catheter (Tokai Medical Products) and a Vassallo GT 18 190 cm wire (Cordis Corp., Santa Clara, CA, USA), we successfully crossed through the center of the calcification via a parallel-wire technique while maintaining the previous wire in the true lumen (Figure 1E, Video 2). The wire was then changed to a CHIKAI 14 315 cm wire (Asahi Intecc), and the Prominent Raptor penetration catheter was removed. A Gateway 2.0–9 mm OTW balloon was guided and applied a total of 6 times (6–12 atm). The procedure was then switched to a SHIDEN 3.0–20 mm balloon. During balloon dilatation at 6 atm, fluoroscopy confirmed that the calcified components were fractured (Figure 1F). The procedure was then switched to an Aperta NSE PTA Balloon 5.0–40 mm (Nipro Co., Osaka, Japan), which confirmed good expansion at 6 atm. IVUS passed, showing a minimum lumen diameter of 2.1 mm × 3.0 mm with circumferential high-density plaque (Figure 1G). An open-cell PRECISE stent 6–30 mm (Cordis Corp.) was selected for its high radial force to overcome expected elastic recoil. This was followed by post-dilatation with the Aperta NSE PTA Balloon 5.0–40 mm at 20 atm. Although 20 atm is extraordinarily high, the risk of rupture was determined to be low because IVUS confirmed a reference external vessel diameter of approximately 8.0 mm, and the 5.0 mm balloon was positioned securely within the fractured center of the plaque, resulting in well-dilated stent placement (Figure 1H). IVUS showed a minimum in-stent diameter of 2.8 mm × 5.2 mm with no in-stent plaque protrusion (Figure 1I). Final angiography showed good dilatation of the stent and antegrade ICA flow, which was still collapsed (Figure 1J). During balloon expansion, a pacing waveform was always observed. The total operative duration was 3 hours, with less than 100 mL of blood loss.

To prevent cerebral hyperperfusion syndrome, the patient’s postoperative systolic blood pressure was strictly controlled below 120 mmHg. A postoperative diffusion-weighted MRI performed the following day revealed no high-signal areas suggestive of new ischemic lesions. The postoperative course was favorable with no neurological deficits. The patient was highly satisfied with the minimally invasive endovascular approach, allowing her to return to her daily life without neurological deficits. CTA 3 days after the procedure showed good stent dilatation and fractured calcified plaque (Figure 2A). The patient was discharged on postoperative day 4. Three months later, angiography confirmed good expansion, and the collapse of the ICA had improved (Figure 2B). At the 18-month follow-up, there was no evidence of restenosis or recurrent stroke.

Figure 2 Postoperative imaging follow-up. (A) CT angiography 3 days post-procedure showed good stent dilation and fractured calcified plaque. The lesion had shifted laterally compared to its preoperative position. Left: carotid lesion, axial image; right: sagittal image. (B) Angiography after 3 months showed good stent dilation and restored ICA flow. Arrows indicate ICA. CT, computed tomography; ICA, internal carotid artery.

Discussion

This case involved severe calcified carotid artery stenosis with eccentrically located calcifications, where even a stiff guidewire had difficulty passing through. Initial pre-dilation using a small balloon catheter (3 mm) did not achieve sufficient expansion of the stenotic segment. Given the high risk of vascular injury associated with larger balloons, a 3.0-mm Shockwave lithotripsy balloon was used to crack the deep calcifications. Despite the small size of the lithotripsy balloon used, the procedure successfully modified the calcified plaque, enabling the parallel-wire technique. This allowed for the passage of a second, stiff wire directly into the severely calcified plaque while maintaining the initial wire in the eccentric true lumen. This was followed by fracturing the plaque with a 5-mm NSE balloon and subsequent stent expansion. The synergy between IVL and the parallel-wire technique was the key to procedural success. While the initial wire was restricted to the eccentric true lumen, IVL-mediated sonic waves created micro-fractures within the deep calcium. These fractures modified the plaque’s compliance, allowing the penetration catheter to establish a new, central axis. This strategic shift converted a technically ‘uncrossable’ lesion into a treatable one.

IVL’s energy is not dependent on static barometric pressure, proportional to the balloon’s expansion diameter. Instead, IVL delivers ultrashort pulses of high-intensity acoustic energy with only low-pressure balloon inflation. Its energy is distributed uniformly, targeting calcium deposits throughout the entire circumference of the vessel, thereby minimizing mechanical vascular damage (8,18,20). IVL is particularly suitable for eccentric calcified lesions because it emits sound pressure waves in a circumferential cross-wall manner under low balloon expansion pressure, generating circumferential calcium cracks on multiple planes without affecting the soft tissue inside the blood vessels (21). The Disrupt CAD II study, a prospective, multicenter, single-arm post-approval study, confirmed the safety and effectiveness of IVL for severe coronary artery calcification. In the study, IVL was safely performed with high procedural success and minimal complications, resulting in substantial calcific plaque fracture, despite the high prevalence of eccentric lesions in 28.3% of cases (22). A reflective evaluation of this case highlights that the primary unexpected danger of this technique—high-pressure post-dilation centrally through the plaque—is the risk of vessel rupture or extensive dissection. However, this risk was meticulously mitigated by our preoperative IVUS assessment, confirming an 8.0 mm vessel diameter against a 5.0 mm balloon. Furthermore, a covered stent was prepared on-site as an essential bailout strategy in the event of a catastrophic rupture.

Rotational and orbital atherectomy are also effective techniques for managing severe calcified lesions that are resistant to balloon angioplasty in peripheral and coronary interventions; however, it was not suitable for the eccentric calcified lesions. The rotation atherectomy (RA) burr has only one axis of rotation on the RotaWire, which rotates along the peripheral orbit of the blood vessel to perform plaque ablation, constantly coming into contact with the plaque. This makes dissection and perforation more likely in eccentric lesions (21,23,24). A previous study reported by Zhao et al. compared IVL and RA in the treatment of calcified coronary lesions and found that procedural complications were higher in the RA group than in the IVL group, including issues such as slow/no reflow and flow-limiting dissection (21). There are a few reports on the use of rotational and orbital atherectomy for calcified carotid lesions (23). This is because they present higher risks of dissection, perforation, and distal embolization compared to IVL (8,20,24). As a result, these techniques are not widely used for carotid arteries. Regarding long-term patency, studies in peripheral interventions by Toyoshima et al. have shown that subintimal wire passage carries a higher restenosis rate than intraluminal passage (25). Crucially, our technique does not rely on subintimal tracking; instead, IVL modifies the plaque to allow the reconstruction of an ideal central intraluminal axis through the true lumen. This mechanistic difference likely explains the sustained patency observed in our patient at 18 months.

The use of IVL for carotid artery stenosis has been primarily employed in patients who are at high risk for CEA. Grillo et al. first reported in 2018 a case detailing a patient with severely calcified ICA stenoses. Due to several comorbidities and hostile neck anatomy, the patient was at high risk for CEA and underwent CAS. IVL was performed before the dilation of the lesion, resulting in subsequent good stent expansion (11). Vadalà et al. reported two complex cases of severe calcified carotid lesions treated successfully with IVL and CAS (15). Misztal et al. also reported a case using IVL for heavily calcified carotid stenosis. These authors suggested that IVL at the carotids is feasible and facilitates stenting of calcified lesions, avoiding complications associated with aggressive conventional balloon angioplasty (14). In 2021, Giannopoulos et al. reported on 21 high-surgical-risk patients with heavily calcified carotid artery lesions, including 19 de novo cases and 2 in-stent restenoses (ISR). In 19 patients, IVL was followed by stent implantation, while the 2 ISR lesions were dilated only. The mean IVL balloon diameter was 4.64±1.13 mm, and the mean number of IVL pulses applied was 67.2±61.4 (range, 10–180). All procedures were technically successful, and no patients developed symptomatic bradycardia or hypotension due to IVL. There were no adverse events associated with IVL delivery. Carotid duplex ultrasound identified significant restenosis (>70%) in one asymptomatic patient at 12 months after the index procedure. No patients required reintervention during a median follow-up of 6 months (range, 1–12 months). They concluded that IVL can be a safe and effective approach for managing severely calcified carotid lesions (16).

This report has several limitations, primarily its nature as a single-case study. Furthermore, the lack of transcranial Doppler (TCD) monitoring and debris quantification limits our ability to fully evaluate the occurrence of microembolic signals and the exact embolic load generated during the procedure. While the outcomes were favorable, safety and efficacy cannot be generalized. The reproducibility, long-term patency, and strict anatomical conditions (e.g., avoiding highly tortuous lesions) for the IVL-facilitated parallel-wire technique require further validation through prospective, multi-center studies.

Conclusions

This case highlights the effectiveness of IVL for treating severely calcified, eccentric carotid artery stenosis. Conventional balloon angioplasty methods often pose a risk of vascular injury, especially in eccentrically located calcified lesions, due to limited luminal gain and the potential for dissection. By using sonic pressure waves, IVL allows for the safe and effective modification of calcified plaques. IVL may be a feasible and potentially effective rescue option for treating severely calcified, eccentric carotid artery stenosis. By modifying plaque compliance, IVL can act as a technical facilitator to establish a central wiring axis via the parallel-wire technique.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the CARE reporting checklist. Available at https://jni.amegroups.com/article/view/10.21037/jni-26-0002/rc

Peer Review File: Available at https://jni.amegroups.com/article/view/10.21037/jni-26-0002/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jni.amegroups.com/article/view/10.21037/jni-26-0002/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. Given the off-label status of IVL in the carotid artery, the procedure was performed following approval from our institutional review board (IRB) and with the Declaration of Helsinki and its subsequent amendments, and specific written informed consent regarding the off-label use was obtained from the patient.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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