Procedure hopes to give stroke victims extra time for treatment
Posted May 7, 2008 5:26 p.m. EDT
Updated May 13, 2008 7:39 p.m. EDT
Chapel Hill, N.C. — When a person is having an acute stroke, every minute of delayed treatment means a higher risk of permanent brain damage. A new procedure, available at UNC Hospitals, hopes to increases a person’s window of treatment up to eight hours.
A stroke is caused when a blood vessel that carries oxygen and nutrients to the brain is either blocked by a clot or bursts, according to the American Stroke Association (ASA). When the vessel is blocked, part of the brain cannot get the blood and oxygen it needs, so it starts to die.
A MERCI (Mechanical Embolus Removal in Cerebral Ischemia) Retrieval System can be used to remove blood clots from the brains of people suffering strokes. The device is a tiny corkscrew sent to the brain through a catheter to remove the clot.
UNC Hospitals is one of only a few hospitals in the state offering a new catheter procedure - Penumbra - to reach even smaller brain vessels.
“By using that we can basically suck out a clot from the brain and restore normal blood flow,” said Dr. Sten Solander, an interventional endovascular neurosurgeon at UNC.
Solander and UNC neurologist Dr. Souvik Sen can spot a blockage with a special CT Scan. Sen said the CT image will show an abrupt cut off of blood flow to one side of the brain.
With X-ray guidance, Solander sends the Penumbra catheter tip to the blockage point. Similar to a straw, an exterior vacuum pump traps the clot and pulls it out.
“This is after the procedure where we have revascularized and opened up the normal blood supplies,” Solander said , pointing to an x-ray that shows restored blood flow in the brain.
Study data that compares the effectiveness of the MERCI Retriever system and the Penumbra System varies.
Dr. Souvik Sen cited data in unpublished trial results presented at the 2008 stroke meeting of the American Stroke Association. That data shows the MERCI system was effective in restoring normal blood flow in 46% of patients while Penumbra was effective in 82% of patients. The recovery data is more difficult to compare. The same ASA data shows Penumbra demonstrated neurological improvement at discharge (recovery) in 58% of patients. Similar data was not available for the MERCI system - but the ASA data includes 30 day recovery of mRS (modified Rankin Score)</=2 at 22.6% - meaning those patients considered, for most purposes, back to normal.
Andrew Gordon, Senior Vice President for Sales and Marketing for Concentric Medical, Inc., which developed and markets the MERCI Retrieval System, cites data from the multi MERCI clinical trial. That data shows MERCI was effective in completely restoring blood flow in 68.3% of patients. Recovery, defined as 90 days post treatment where patients have an mRS</=2, was achieved in 49% of patients. Gordon says the same definition of recovery was achieved in only 29% of patients in Penumbra's trial. Gordon adds though the FDA cleared the use of Penumbra to within an 8 hour limit after the first stroke symptoms, they approved the MERCI system with no maximum time limit.
UNC's Dr. Sten Solander says doctors don't discount either system based on these comparisons. He says, "Both devices work, and the results are very much depending on how soon the patients are treated. I do like to compare it to having a driver AND a putter, rather than having a driver OR a putter. "
Regarding Penumbra's effectiveness, Dr. Sen says “It is huge. I do not think we've had another treatment show such a huge impact in reversing the stroke disability in the early stages.”
Penumbra is currently available at UNC and Duke. WakeMed plans to make it available in June.
Despite the new technology that extends the window of treatment time, getting to the hospital as soon as possible is still recommended.
A simpler procedure to prevent permanent brain damage - a clot-busting drug called tPA – can be administered if the patient arrives within two hours of the first symptoms. It takes another hour to see if the injection will help. Generally, only 3 to 5 percent of those who suffer a stroke a stroke reach the hospital in time for this treatment, according to the ASA.
Symptoms of a stroke include numbness or weakness on one side of the body, sudden vision loss, a headache and slurred speech. People experiencing symptoms of a stroke are urged to call 911.