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Stenting for Intracranial Atherosclerotic Disease: An Option Beyond Aspirin
Abstract & Commentary
By Alan Z. Segal, MD, Associate Professor, Department of Neurology, Weill-Cornell Medical College, Attending Neurologist, NewYork-Presbyterian Hospital. Dr. Segal is on the speaker's bureau for Boehringer-Ingelheim.
Synopsis: Intracranial stenting is a promising new technology for secondary stroke prevention, but needs to be studied in a randomized trial against best medical therapy.
Source: Bose A, et al. A novel, self-expanding, nitinol stent in medically refractory intracranial atherosclerotic stenoses: The Wingspan Study. Stroke.2007;38:1531-1537.
Surgical treatment of atherosclerotic stenoses in the intracranial circulation has been limited to unproven surgical procedures, such as EC-IC (extracranial to intracranial) bypass. Medical management is limited to anti-platelet therapy with aspirin, since the results of the Warfarin-Aspirin Symptomatic Intracranial Disease (WASID) trial showed that warfarin therapy provided no added benefit for stroke prevention and significantly increased the risk of major bleeding. Reports of endovascular treatment for intracranial stenosis have included case series using coronary angioplasty balloons and balloon expandable stents. The Wingspan device was designed specifically for the cerebral vasculature, and thus may offer a superior safety and efficacy profile for these high-risk patients.
Bose et al treated 45 patients with the Wingspan device. Each had intracranial stenosis and were refractory to medical therapy. The degree of stenosis was reduced from 75% to 32% post procedure, and 28% at 6-month follow up. It was notable that the vessels further improved over time post-stenting indicating a process of stent-associated vascular remodeling. The rates of adverse events were low, with a 4.5% composite ipsilateral stroke/death rate at 30 days and a 6-month stroke/death rate of 7%. Physician reported follow up over an average of 13 months showed comparable results, with one additional stroke reported. Stents were most commonly placed in the middle cerebral artery M1 segment (n = 10), petrous carotid (n = 5) or the vertebral artery (n = 13). Eighteen procedural related complications were reported in 12 patients, but none of these resulted in permanent sequelae.
The authors' discussion elucidates how the Wingspan device is different from balloon-expandable stents. Because the angioplasty balloon for Wingspan is undersized and inflated at a much lower pressure, there is much less risk of trauma to the atherosclerotic vessel. The self-expanding Wingspan stent is flexible and can navigate through and conform to tortuous vessels. In contrast, a balloon expandable stent must be oversized in order to properly appose to the vessel wall.
This study confirms that the Wingspan stent can be safely and effectively deployed to treat atherosclerotic lesions in the intracranial vasculature. Even without a head-to-head comparison, this device appears to be favorable to stents designed for the cardiac circulation, not the brain. These data also compare favorably to the data from the WASID study, which showed a 12% per year stroke rate in these high-risk patients. Among patients with the most severe stenoses in WASID (>70%), one-year stroke risk was 23%. Overall WASID patients had milder stenoses (mean 64%) than in the present study (mean 75%). In conclusion, although the Wingspan results certainly appear tantalizing, randomized comparison between stenting and medical management will be needed to confirm these results.
What about stenting for extracranial vertebral artery stenosis?
In a sub-study to the much larger CAVATAS trial for stenting of carotid stenosis, (Coward LJ, McCabe DJH, Ederle J et al. Stroke 2007; 38: 1526), the investigators included 16 cases of symptomatic vertebral artery stenosis. Eight patients with vertebral artery origin stenosis were treated with stenting, while eight patients were treated medically (of these, one had distal disease). During a mean follow-up period of 4.7 years, no patient in either treatment arm had a stroke. Three patients in each treatment arm died of myocardial infarction or carotid territory stroke and one endovascular patient had a nonfatal carotid territory stroke.
As the authors conclude, this trial was unable to prove a benefit for vertebral artery stenting, but the numbers were quite small. More importantly, these patients were at risk for other types of vascular events thus mandating a broad approach to atherosclerotic risk reduction.
Unlike the patients in Wingspan and WASID, who had severe intracranial atherosclerotic disease, these CAVATAS patients, with vertebral artery origin disease, appeared to be at quite low stroke risk. The vertebral circulation has a built-in redundancy, with one dominant vertebral feeding the basilar and a smaller non-dominant vessel. Therefore, atherosclerotic lesions at one vertebral origin may not warrant as aggressive intervention and may be, in most cases, managed medically.