Intravascular lithotripsy prior to transcarotid arterial revascularization: A technical tale of two cases

Abstract

calcific carotid stenosis is becoming more common as the advanced-age population grows, requiring new therapeutic approaches. As such, transcarotid arterial revascularization is gaining significant popularity in the management of carotid stenosis due to low rates of perioperative complications and optimal clinical outcomes. In addition, intravascular lithotripsy has shown promise in safely facilitating the success of endovascular procedures in the context of calcified lesions. The combination of neuroprotective technology offered by transcarotid arterial revascularization and circumferential plaque remodeling by intravascular lithotripsy has been utilized for complex lesions. We present two cases of symptomatic calcific carotid stenosis treated with intravascular lithotripsy before transcarotid arterial revascularization. A 4 × 40 mm lithotripsy balloon delivered shockwaves at two and four atmospheres over a 0.014 wire. Transcarotid arterial revascularization was successfully completed without complications, and luminal patency was observed in both patients. Calcific carotid stenosis was effectively treated with intravascular lithotripsy before transcarotid arterial revascularization, resulting in optimal safety and clinical recovery. Thus, when combined with novel shockwave technology, the neuroprotective effect of flow reversal in transcarotid arterial revascularization procedures demonstrates promise in maintaining safety while providing a novel treatment technique for high-risk patients with calcific cervical internal carotid artery stenosis.

Introduction

Calcific carotid stenosis (CCS) is a widely prevalent pathology, especially in the advanced-age population. The prevalence of asymptomatic CCS is likely underreported in current literature as surgical intervention is only indicated when patients experience cerebrovascular accident or syncope. In 2014, over 30,000 patients of the United States Medicare population received carotid endarterectomy (CEA) while 10,000 underwent carotid artery stenting (CAS) for carotid stenosis, which underscores the necessity of surgical intervention in this age cohort. ¹ The underlying pathophysiology is multifactorial and is likely attributed to endothelial dysfunction, chronic vascular inflammation, oxidative stress, and/or the failure of other cell regulatory systems. ² Conventional endovascular intervention in the setting of CCS includes CAS or CEA. Moreover, transcarotid arterial revascularization (TCAR) has become widely popular, as this technique has demonstrated decreased rates of in-hospital transient ischemic attack (TIA), stroke, and death when compared to CAS, ³ likely due to the neuroprotective effect of flow reversal. Interestingly, the off-label addition of shock wave therapy (in the form of intravascular lithotripsy (IVL)) to TCAR has demonstrated safety and utility in decreasing the calcium burden of patients with circumferential or high-grade CCS.^4,5 Herein, we are reporting two cases of calcified cervical internal carotid artery (ICA) stenosis successfully treated with IVL prior to TCAR, yielding favorable postoperative angiographic results and optimal clinical outcomes.

Case 1

A 76-year-old female with a past medical history of Parkinson’s disease, breast cancer (status post-resection), multiple presyncopal episodes, and TIA manifesting as transient limb ataxia presented to an outside hospital following a syncopal episode lasting 30 to 40 min. After losing consciousness during micturition, she was subsequently transported to an outside institution for a workup of a cardiovascular accident. Imaging at that time was unremarkable. However, her blood pressure was 239/97 mmHg, which necessitated treatment with labetalol. In addition, laboratory findings were significant for elevated creatine kinase and troponin levels (357 U/L and 49 ng/L, respectively). Of note, no motor or sensory deficits were appreciated upon neurologic examination. She then experienced a near-syncopal episode shortly after being discharged, prompting evaluation at our institution.

Bilateral carotid Doppler ultrasound indicated moderate to severe calcification with atherosclerosis, demonstrating greater than 70% stenosis of the right ICA and less than 50% stenosis of the left ICA. Despite marked stenosis, the normal flow of the ICA was observed bilaterally. These findings were subsequently confirmed with computed tomography angiography (CTA) (Figure 1). Taking into account the repeated presyncopal episodes and TIA symptoms, the decision was made to pursue TCAR with balloon angioplasty. Furthermore, the high calcific burden of the right ICA qualified this patient for IVL. The patient was started on 81 mg of aspirin and 75 mg of clopidogrel by mouth once daily for 7 days prior to the procedure. Vascular access was achieved via the left common femoral vein, in which an 8-French sheath from the flow reversal circuit was placed. An incision was made above the sternocleidomastoid, in which approximately 3 cm of the common carotid artery (CCA) was exposed via blunt dissection technique. Seven thousand units of heparin were then administered to achieve a clotting time of >250 s prior to arterial access. The TCAR Silk Road sheath was advanced 2.5 cm into the CCA, which was connected to the circuit, and flow reversal was subsequently confirmed.

Figure 1.

CT angiography of Case 1 demonstrating marked calcific stenosis (yellow arrow) of the right cervical ICA just distal to the carotid bifurcation in the a) axial and b) sagittal planes.

CT: computed tomography; ICA: internal carotid artery.

Once the flow reversal circuit was in place and the calcified plaque identified, a 4 × 40 mm lithotripsy balloon over a 0.014 wire was used to traverse the stenosis (Figure 2(a)). Lithotripsy was performed at two and four atmospheres. Angioplasty was performed with a 5 × 20 mm balloon at six atmospheres, then exchanged for an 8 × 40 mm Enroute stent spanning the lesion (Figure 2(b)). No significant change in vitals was noted. Flow reversal time was 12 min. Following the procedure, hemostasis was achieved via a purse-string suture across the site, and 30 mg of protamine was administered. No residual stenosis was observed.

Figure 2.

Intraoperative X-ray images of case 1 demonstrate successful placement of the (a) 4 × 40 mm shockwave lithotripsy balloon and (b) 8 × 40 mm Enroute stent across the lesion. The yellow (a) circle and (b) arrows indicate the outline of the lithotripsy balloon and Enroute stent, respectively.

Preoperative angiography showed stenosis of the right ICA (Figure 3(a)), while postoperative angiography confirmed vessel patency (Figure 3(b)). The patient had no perioperative complications or neurological deficits and recovered to her neurological baseline. She was discharged in stable condition on postoperative day 2, and no further symptoms were reported during the subsequent follow-up.

Figure 3.

CT angiography of case 1 demonstrates (a) significant preoperative stenosis of the right ICA and (b) patency of the vessel following TCAR with IVL.

CT: computed tomography; TCAR: transcarotid arterial revascularization; IVL: intravascular lithotripsy; ICA: internal carotid artery.

Case 2

A 64-year-old female with a past medical history of untreated hypertension presented to our institution with left hemiparesis and sensory loss and was found to have severe stenosis of the left ICA and moderate stenosis of the right ICA on CTA. She had an NIH stroke score of 1, and as such, did not qualify for treatment with tissue plasminogen activator or thrombectomy and was managed medically with complete resolution of symptoms. Subsequent neurosurgical follow-up revealed bilateral proximal ICA atherosclerotic calcific disease with greater than 70% stenosis on CTA (Figure 4). Flow velocity on ultrasound revealed a maximum peak systolic velocity of 320 cm/s with normal direction of flow and flow pattern. However, she experienced shortness of breath with exertion, qualifying her for surgical intervention.

Figure 4.

CT angiography of case 2 demonstrates marked calcific stenosis of the right cervical ICA at the carotid bifurcation in the (a) axial and (b) sagittal planes. Yellow arrow indicates calcification.

CT: computed tomography; ICA: internal carotid artery.

Given the patient’s marked stenosis and high calcific burden, the decision was made to perform the right TCAR with balloon angioplasty and concurrent IVL. The patient was started on 325 mg of aspirin and 75 mg of clopidogrel by mouth for 14 days prior to the procedure. The CCA of 3 cm was exposed in a fashion similar to the aforementioned case. Heparin was then administered to achieve a therapeutic clotting time of >250 s prior to arterial access, in which a French non-stiffened micropuncture set was used to access the CCA. The transcarotid arterial (TCAR Silk Road) sheath was then advanced 2.5 cm into the CCA and assessed for proper positioning under fluoroscopy. The flow reversal circuit was completed, after which flow reversal was confirmed via saline bolus delivery.

The right ICA lesion was crossed via a 4 × 40 mm Shockwave balloon over a 0.014 exchange length guidewire (Figure 5(a)), in which two rounds of IVL were performed. The balloon was then removed and an 8 × 40 mm Enroute stent was placed across the lesion (Figure 5(b)). Preoperative angiography redemonstrated stenosis of right ICA (Figure 6(a)), whereas postoperative CTA confirmed patency of the vessel (Figure 6(b)). The patient tolerated the procedure well and suffered no neurologic deficits. Postoperatively, carotid ultrasound demonstrated patent flow of the right distal CCA and proximal ICA (Figure 6(c) and (d)). She was discharged on postoperative day 2 and reported no neurologic symptoms at the 15-day follow-up.

Figure 5.

Intraoperative X-ray images of case 2 demonstrate successful placement of the (a) 4 × 40 mm shockwave lithotripsy balloon and (b) 8 × 40 mm Enroute stent across the lesion.

Figure 6.

CT angiography of case 2 demonstrates (a) significant preoperative stenosis of the right cervical ICA and (b) patency of the vessel following TCAR with IVL; color Doppler ultrasound demonstrating stent patency of the (c) right distal CCA extending into the (d) right proximal ICA on POD 1.

CT: computed tomography; POD: postoperative day; CCA: common carotid artery; ICA: internal carotid artery; TCAR: transcarotid arterial revascularization; IVL: intravascular lithotripsy.

Discussion

The clinical benefits of TCAR for cervical ICA stenosis have been well characterized in the literature, which includes the unique advantages of shorter operative time, lower risk of cranial nerve injury, and minimal blood loss compared to other endovascular techniques.^3,6 In addition, the application of IVL prior to endovascular procedures has shown promise in the management of peripheral artery, coronary, aortic arch, and carotid lesions,^7–10 although literature regarding the use of this technology within the context of open procedures (such as TCAR) remains significantly limited. Overall, TCAR appears to provide optimal clinical outcomes with high rates of success and favorable complication profiles.^6,11,12 Moreover, preliminary data suggest that the addition of IVL may provide a marked benefit in patients with significantly calcified and/or circumferential stenosis,^4,5 in addition to facilitating the revascularization of otherwise procedurally challenging calcified plaques. In the above cases, calcified lesions were considered circumferential if they involved both sides of the carotid intima (Figures 1 and 4) and were therefore amenable to the IVL procedure.

As demonstrated in these cases, IVL may offer a significant benefit when used in conjunction with TCAR procedures. Notably, each procedure resulted in lumen patency (Figures 3 and 6). In addition, color Doppler ultrasound confirmed patency of the cervical ICA in the early postoperative period of case 2, further highlighting the potential success of this novel technique. The prognosis of each patient was significantly improved following each procedure, given that TCAR is associated with a 72% decrease in stroke alone and a 65% reduction in risk of stroke or death compared to more conventional treatment options such as transfemoral CAS. ¹³ It must be emphasized that proper patient selection is vital to the success of such operations. The cases above were preoperatively assessed based on the location of the occlusive lesion in the ICA, in addition to the calcified nature of each lesion. It is recommended to pursue TCAR only for cases in which the following anatomic criteria are met: distance between the CCA above the clavicle and the lesion is greater than 5 cm, the diameter of the CCA is greater than 6 mm, and access to occlusion sites of the carotid artery are relatively disease free. Given these specifications, some have found that only 85% of angiographically identified stenotic carotid arteries remain eligible for TCAR. ¹⁴ In light of the observed safety of this evolving technique and a high proportion of patient eligibility, this technology may be considered in endovascular intervention as a whole.

In the cases presented here, the use of IVL prior to TCAR may have provided a safe method of reducing the calcific burden. It is possible that the neuroprotective effect of flow reversal in TCAR may retain a high level of safety when combined with novel IVL technology, therefore providing an additional treatment option for high-risk patients. Furthermore, patients with heavily calcified or circumferential lesions may particularly benefit from this innovative technology. Future study is required to elucidate the safety and complication profile of IVL prior to TCAR in those with CCS. However, the addition of these cases to the current neurovascular literature emphasizes the potential safety of these technologies when used adjunctly. Due to optimal anatomic positioning and delivery of radiofrequency waves within the artery, IVL prior to TCAR utilizes the distinct advantage of decreasing the calcium burden in those with circumferential calcifications, which has been a well-documented challenge of conventional endovascular methods.

Conclusion

CCS is increasingly prevalent in patients of advancing age. IVL effectively modifies heavily calcified lesions via lithotripsy-driven fracture. Here, we address two cases of CCS that were successfully treated with IVL before TCAR, resulting in favorable clinical and radiographic outcomes with a good safety record. Therefore, these cases demonstrate that CCS was effectively treated with IVL before TCAR, ensuring optimal safety and clinical recovery. Consequently, combining innovative shockwave technology and the neuroprotective effect of flow reversal in TCAR procedures promises enhanced safety and new treatment options for high-risk patients with calcific cervical ICA stenosis.