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Technical Innovation |
1 All authors: Department of Radiology, Emory University School of Medicine, 1364 Clifton Rd., N.E., Atlanta, GA 30322.
Received May 13, 1999;
accepted after revision July 15, 1999.
Address correspondence to G. J. Joseph.
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A 65-year-old woman presented with a 5-day history of headaches associated with episodic left hemianesthesia and perioral numbness. On the day before admission, she experienced sudden onset of left hemiparesis and dysarthria, followed by a brief syncopal episode that completely resolved. MR imaging and MR angiography revealed small bilateral cerebellar hemispheric infarcts and a right occipital lobe infarct with a focal flow gap in the proximal basilar artery. She was transferred to our institution and stabilized in the intensive care unit with a combination of volume expansion, anticoagulation with heparin, and pressor therapy to maintain a mean arterial pressure of 110-120 mm Hg. On physical examination she had no neurologic deficits.
Cerebral angiography (Figs. 1A and 1B) revealed high-grade eccentric ulcerated stenosis in the proximal basilar artery extending to the origin of the anteroinferior cerebellar arteries. After stabilization on medical therapy, the patient was mobilized in an attempt to wean her from pressor and volume expansion therapy; however, simply rising to a sitting position at the bedside resulted in transient dysarthria and near syncope.
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After femoral artery sheath placement, prophylactic antiplatelet therapy using IV abciximab (Reopro; Eli Lilly, Indianapolis, IN) was added to the anticoagulation regimen. Activated clotting time was adjusted to just over 300 sec. A 6-French Envoy guiding catheter (Cordis Neuroradiology, Miami, FL) was placed in the left vertebral artery at the level of C3. Using digital road-map fluoroscopy, we crossed the lesion with a Choice PT Extra Support 300-cm (0.014-inch) hydrophilic guidewire (Scimed-Boston Scientific, Maple Grove, MN). Angioplasty was performed with a 3-mm Ranger balloon (Scimed-Boston Scientific). A total of four inflations were made to 8 atm (8.08 x 105 Pa). The balloon was gradually inflated to maximum pressure over 10-20 sec and remained inflated for no longer than 20 sec at maximum pressure. Two angiograms were obtained after dilation showing no significant improvement in the luminal diameter (Fig. 1C). Guidewire access was maintained across the stenosis and the balloon was exchanged for a premounted 3-mm diameter, 12-mm length GFX coronary stent (Arterial Vascular Engineering-Medtronic, Santa Rosa, CA). This stent was centered and deployed across the lesion, with the distal end of the stent below the origins of the anteroinferior cerebellar arteries and the proximal end extending down the left vertebral artery. The balloon was inflated to 9 atm (9.09 x 105 Pa) (nominal pressure) to deploy the stent. Angiography after deployment showed excellent results with good positioning below the patent anteroinferior cerebellar arteries and a widely patent basilar artery (Fig. 1D). The patient was maintained on IV heparin for 24 hr. CT images revealed no evidence of silent infarct. The patient made an uneventful recovery with no neurologic deficit on independent neurologic examination. She was given aspirin (325 mg/day) and clopidogrel (Plavix; Bristol-Myers Squibb, New York, NY) (75 mg/day) and discharged. At 6-week follow-up, transcranial Doppler sonography revealed no evidence of velocity elevation through the stented segment of the basilar artery. The patient remained neurologically healthy.
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Phatouros et al. [6] described a single case of endovascular stenting of a basilar artery. In that case, the patient presented with a basilar occlusion requiring thrombolysis. Once patency was established, balloon dilation of an underlying stenosis was unsuccessful in establishing an acceptable luminal diameter, probably as a result of elastic recoil. A 4-mm Gianturco-Roubin-2 coronary stent (Cook Cardiology, Bloomington, IN) was successfully used to increase basilar artery patency. The patient unfortunately died as a result of complications of a periprocedural myocardial infarction. To our knowledge this represents the only other reported placement of a stent in the basilar artery to treat symptomatic atherosclerotic occlusive disease.
Mori et al. [7] described a case of primary angioplasty with stenting of an acutely thrombosed intracranial vertebral artery without using initial thrombolytic therapy. After dilation with a 2.5-mm balloon, residual stenosis was present probably as a result of undersizing of the balloon. Those authors used the same stent as in our case and described similar relative ease of deployment and posttreatment patency.
In our patient, elastic recoil likely occurred after otherwise technically successful angioplasty. On the basis of the diagnostic angiogram, the plaque appeared to be rather eccentric and may have accounted for the degree of recoil observed. The balloon was sized to exactly match vessel size based on both direct comparisons to a standard taped to the patient's head and by using internal calibration software. The balloon inflation pressure was greater than the nominal pressure needed to obtain the 3.0-mm inflated diameter, and inflations were performed using road-map imaging to ensure proper positioning. In the peripheral circulation, inflation with an oversized balloon may prevent recoil and allow an acceptable result; however, in our opinion, oversizing baloons in the cerebral circulation increases the risk of vessel rupture or dissection.
The deployed stent was chosen on the basis of its flexibility, low profile, and radiopacity. Flexibility is high because of the connected "crown" configuration that distributes the "spine" or longitudinal support in helical rather than more rigid linear fashion around the stent circumference. This configuration does not rely on hinged elements for flexibility, as do many tubular slotted designs. The low profile results from a premounted edgeless design that positions the stent in grooves formed on the balloon surface to reduce irregularities that might result in friction with the vessel wall or plaque. This design stabilizes the stent on the balloon and protects it from inadvertently dislodging, especially when tracking outside the guiding catheter through the relatively tortuous anatomy of the vertebrobasilar system. The distal end of the balloon catheter is hydrophilic, which enhances tracking.
In our patient, stent deployment required modest wire and catheter manipulation to achieve proper positioning in the basilar artery. The anatomy of the proximal vertebrobasilar system in this patient was favorable for stent placement. Moderate tortuosity at the origin of the vertebral artery was straightened with placement of the guiding catheter without compromising antegrade flow, and stent placement ensued easily. Such success cannot be anticipated, however, in a patient with an unfavorable anatomy because of shortcomings in stent designs currently available.
The issue of perforator and side branch "jailing" with potential for occlusion is an important one. Experience with coronary side branch coverage indicates relatively low risk of larger branch vessel occlusion when these vessels have little to no plaque involvement [8]. In this case, the stent was deliberately deployed across the right vertebral artery termination and could potentially jail basilar perforators. The metallic surface coverage is 20% of the total stent surface area, which is at the upper end of the range of currently available coronary stents. Despite this coverage, we saw no clinical evidence of perforating vessel infarct after the procedure or at the 6-week follow-up.
The technical difficulty and complication rates are significant for balloon angioplasty alone; therefore, it is premature to suggest that all angioplasty for symptomatic intracranial stenosis should be accompanied by stent placement. Our case indicates that stent-assisted angioplasty in the basilar artery is at least technically possible and may provide a method of improving outcome in suboptimal angioplasty.
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  C. C. Phatouros, J. E. Lefler, R. T. Higashida, P. M. Meyers, A. M. Malek, C. F. Dowd, and V. V. Halbach Primary Stenting for High-grade Basilar Artery Stenosis AJNR Am. J. Neuroradiol., October 1, 2000; 21(9): 1744 - 1749. [Abstract] [Full Text]
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