Pipeline® Embolization: an advanced procedure to stent large proximal carotid artery aneurysms
A device that received FDA premarket approval in April 2011, the Pipeline® Embolization Device allows for true reconstruction of large or giant wide-necked intracranial aneurysms (IAs). The Cleveland Clinic Neurological Institute's Cerebrovascular Center is one of just a few centers in the United States approved to utilize this device.
The Pipeline Embolization Device is a fine-mesh stent that diverts blood flow away from the aneurysm in order to provide a complete and durable embolization while maintaining patency of the parent vessel. The stent is a bimetallic design of 75 percent cobalt chromium and 25 percent platinum tungsten; it comprises 48 densely braided strands. It is “customizable” in that multiple devices can be telescoped together, one inside the next, for longer constructs.
Proximal carotid artery aneurysms larger than 1 centimeter in diameter, which are often dysplastic are notorious for returning after surgery or endovascular procedures. The leading-edge Pipeline stent, which has seen positive success in Europe and South America for more than a year, allows for aneurysm repair that previously would have been dangerous to repair or inoperable.
Essentially, it provides a potential cure for patients who otherwise have very poor long-term prognoses.
Approximately 300,000 brain aneurysms rupture each year, and less than 1 percent of the 300,000 are large proximal carotid artery aneurysms.
Interestingly, patients with these aneurysms are a bit older – age 50 to 70 – than the general population of aneurysm patients, whose age averages 40 to 60. We don't know why that is; it's possible that these aneurysms have simply had an extra decade or so to grow.
Previously, even for experienced neurosurgeons, the risks and outcomes with these large and giant aneurysms have been difficult to predict. There were three choices:
- palliative treatment only.
- traditional brain surgery, in which a hairpin clip is inserted under the cranium, pinching the bubble of the aneurysm shut and allowing the brain and vessels to return to their natural shape.
- an endovascular procedure, in which a catheter is inserted at the thigh and, under X-ray, navigated to the head to allow the insertion of a stent. In some cases, these stents successfully circumvented the aneurysm, but were not successful in preserving the blood vessel. In addition, for aneurysms with no defined bubble – dysplastic aneurysms – placement of the stent was challenging.
The Pipeline Embolization Device gives us another option: one specifically designed for this type of large aneurysm, which, even if surgery or an endovascular procedure is successful, often have recurred.
Previous generations of stents have allowed us to remodel the vessel around the aneurysm. Stents in general led to good outcomes in many cases by generating not only mechanical benefits, propping up the vessel wall, but biological benefits as well. As the vessel remodels itself and overgrows the stent, the vessel lining can actually grow over the stent, further strengthening the vessel.
But older stents, because of their mesh construction, have not been completely successful at redirecting blood flow; blood can, in fact, simply flow through the mesh.
The new device provides a mesh so tightly woven that it does redirect blood flow past the aneurysm so that the aneurysm can clot off and heal over itself.
The international success rate with this flow-diverting stent has been stellar: Some 90 to 95 percent of the aneurysms so treated never came back, according to the available literature. To put that in perspective, the risk of complications after simple aneurysm surgery is 3 to 4 percent; the complication rate in other stent procedures has been about 5 percent.