[MIRS-IR Vol III:2; 3/4/99]

Post-Endarterectomy Percutaneous Transluminal Angioplasty and Stenting of the Internal Carotid Artery

Larry Graham II, MD and Edward Hobart, MD

Introduction
Recently, percutaneous transluminal angioplasty (PTA) has become an accepted technique for treating arterial stenosis of supra-aortic vessels. Angioplasty of the supra-aortic vessels was avoided for some time because of the risk of embolization to the central nervous system. Theron et al. have recently advocated carotid angioplasty with the adjunctive use of cerebral protection and additional use of stents, where indicated, for all types of carotid artery stenosis. However, the use of cerebral protection remains a controversial subject. Anderson et al suggest that stent implantation should be an option to treat sub-optimal or unsuccessful PTA results. However, most recently interventional radiologists and cardiologists have utilized primary stenting of carotid stenoses to decrease the initial risk of embolization from atherosclerotic plaque or dissection after PTA .

Background
The three major etiologies of carotid stenosis are atherosclerotic disease, post-endarterectomy stenosis and inflammatory stenosis. Atherosclerotic stenosis most often involves the carotid bifurcation and less commonly the innominate artery, proximal common carotid and carotid siphon. In the post-endarterectomy patients, where endarterectomy was performed for atherosclerotic disease, recurrent stenosis at the carotid bifurcation may occur 6 months to 2 years following the surgical procedure. Post-endarterectomy stenosis is highly amenable to endovascular treatments such as PTA with or without stenting. The most common causes of inflammatory stenosis are radiation therapy, fibromuscular dysplasia and Takayasu arteritis. In most cases, angioplasty is performed initially, using cerebral protection where indicated, and stents are used when there is unsatisfactory results or if there is a dissection.

Case Presentation
A 58 year- old male who had undergone left carotid endarterectomy several years prior presented with a three-month history of blurred vision. The patient had a carotid arteriogram performed at an outside facility which demonstrated >90% restenosis at the origin of the left ICA (figure 1). He was referred to our institution for endovascular treatment of the lesion.

Technique
Using a right common femoral approach, a diagnostic angiogram confirmed the left ICA stenosis of >90%. Due to the severity of the lesion and because it was composed of post-endarterectomy scar tissue, it was elected to stent primarily without attempting initial angioplasty. The lesion was crossed using a 0.035 Glidewire and angle-tip catheter. The Glidewire was exchanged for a Rosen wire. The patient was given an IV bolus of 3,000 units of heparin. After performing appropriate measurements to size the native vessel, an 8 mm x 2 cm WallStent (Boston Scientific Vascular) was placed across the stenosis (figure 2). A 5 mm angioplasty balloon (Medi-tech) was used to expand the mid and distal portions of the stent while a 6 mm angioplasty balloon (Medi-tech) was used to distend the portion that crossed the stenosis. The post-procedural angiogram demonstrated the stent to be good position with no residual stenosis at the origin of the ICA and good wall apposition throughout the length of the stent (figure 3) and (figure 4). The patient tolerated the procedure well and demonstrated no neurologic sequelae. Following removal of the guiding catheter and sheath, hemostasis was obtained at the common femoral artery puncture site using an AngioSeal® device. The patient was placed on a continuous IV infusion of heparin at 1,000 U/hr and was admitted to the intensive care unit for overnight observation.

Outcome
The post-operative course was uneventful and the patient was discharged home the next day. He is currently taking Ticlopidine and ASA and continues to do well with no recurrent symptoms.

Discussion
Symptomatic carotid artery stenosis that reduces the diameter of the vessel by 70% or more carries a significantly higher incidence of stroke if treated medically (up to 26%) compared to surgical treatment. PTA of the cervical segment of the common and internal carotid arteries (ICA) is an alternative to vascular surgery in the treatment of symptomatic carotid artery disease. The potential benefits of PTA of the carotid artery are shortened hospital stay, reduced procedure time and avoidance of general anesthesia. Additionally, there should be a reduction of morbidity and mortality, which is as high as 5-6% following carotid endarterectomy (CEA) in symptomatic patients.

Indications for PTA and/or carotid stent placement are similar to the indications for carotid endarterectomy. Prior to angioplasty, all patients should have hemodynamically significant stenosis (>70%) by Doppler ultrasound (US) and have this confirmed by angiography in at least two projections. Additionally, clinical symptoms such as transient ischemic attacks and previous stroke with moderate residual deficits should be taken into account. Rarely, endovascular treatment of carotid stenosis is performed as an emergency during intra-arterial thrombolysis for ischemic stroke.

PTA is a well accepted technique for treating occlusive diseases in almost all anatomic territories. PTA of the carotid arteries is commonly complicated by significant elastic recoil. Suboptimal results also due to dissection or persistent irregularity of the vessel wall that could serve as a nidus for thrombosis. Additionally, manipulation of guide wires, catheters and balloons, and plaque rupture associated with angioplasty have the potential to give rise to peri-procedural cerebral embolization. Theron et al have described a triple coaxial catheter technique of protected angioplasty (figure 5). A guiding catheter is positioned in the common carotid artery, close to the stenosis of the internal carotid artery at the bifurcation. Next, angioplasty and balloon occlusion catheters are positioned in the internal carotid artery stenosis and in the proximal ICA respectively. The latex occlusion balloon is first inflated, then the angioplasty is performed during ICA flow arrest. The occlusion balloon remains inflated while the angioplasty catheter is deflated and withdrawn. Any atherosclerotic or thrombotic debris is then aspirated through the side port of the guiding catheter. Subsequent flushing of the guiding catheter washes any remaining particulates safely into the external carotid artery. After this the occlusion balloon is deflated and a completion angiogram is performed to assess the results of the PTA. This technique allows dilation of the stenosis even though the plaque may be ulcerated. The angioplasty balloon should be hand inflated with an average of three inflations being performed. The occlusive balloon remains inflated approximately 10 minutes. Temporary occlusion is generally well tolerated and neurologic status can be assessed by asking the patient to move the contralateral hand during the procedure. After employing the use of cerebral protection, Theron et al's complication rate from embolization decreased from 8% (3 of 38 patients) to zero (out of 136 patients) during the treatment atherosclerotic stenoses. However, this technique remains controversial as others have reported higher complication rates with its use.

Stent placement may be performed primarily on high-grade stenoses, or it may be used to complement PTA when angioplasty results are compromised by highly resistant lesions, elastic recoil, dissection or other sub-optimal results. Re-operation after CEA carries a higher complication rate than the original surgery and the lesions are primarily fibrotic, making these patients logical candidates for stent deployment. If used if conjunction with PTA, carotid stents can improve the results of angioplasty in two ways. First, stents protect the arterial wall thereby reducing the risk of dissection, and secondly stents have been shown to reduces the incidence of re-stenosis. Theron et al found that, before stents were accepted for use in the carotid arteries, approximately 5% of carotid PTA resulted in dissection. After they began using stents for unsatisfactory angioplasty results, the residual intimal flap rate dropped to 0%. These investigators also noted a reduction in re-stenosis from 16% to 4% with the adjunctive use of stents. Carotid stenting is has a 12-month primary patency rate of approximately 90%. However, the lack of long-term follow-up data on patency and delayed complications remains a significant obstacle to the widespread use of carotid stents at this time. Improvements in technique and a more aggressive antiplatelet regimen with Ticlopidine may have a positive impact on reducing neurologic complications.

Despite its potential advantages, PTA and stenting of the ICA remains in the early stages of development. The results of the Carotid and Vertebral Artery Transluminal Angioplasty Study (CAVATAS) may prove that PTA or stenting is a safe and effective initial treatment of carotid stenoses. Until then, this treatment should be reserved for patients with specific indications, such as surgically inaccessible lesions, re-stenoses after CEA, significant concomitant medical disease, and fibromuscular dysplasia.