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University of California - Los Angeles

Cause of ischemic stroke analyzed for the first time

Researchers study blockages retrieved by novel mechanical procedure

In contrast to traditional beliefs that stroke-causing clots derived from arterial and cardiac sources are distinctly different, a new UCLA study shows they are composed of similar components.

Researchers studied clots removed from the brain blood vessels of 25 stroke victims. The clots were retrieved during treatment using a novel mechanical clot-retrieval device called the MERCI (Mechanical Embolus Removal in Cerebral Ischemia) Retriever. The removed clots were analyzed under the microscope to compare their component structures.

"Unexpectedly, no two retrieved clots looked the same, even though all were constructed from the same basic components of fibrin, white cells and red blood cells," said lead author Dr. Victor Marder, professor of hematology and oncology at the David Geffen School of Medicine at UCLA and a UCLA Stroke Center member. "The same components were involved in both the newly formed and mature, enlarging clots. Red blood-cell accumulations had previously been considered to dominate the structure of clots that formed within a heart chamber, but our results suggest that red cells often accumulated on clots after impaction in the brain artery."

The findings could lead to better therapies to prevent clots, clear blockages and reverse strokes in the crucial first hours after they occur.

"This could potentially change the way we treat clots," said Dr. Jeffrey Saver, professor of neurology at the David Geffen School of Medicine at UCLA and co-director of the UCLA Stroke Center. "Now that we can retrieve clots, we can analyze their molecular composition and determine the combination of mechanical therapies and clot-dissolving agents most likely to allow us to open up arteries."

This study marks the first time that so many blockages, almost all of which were clots, have been analyzed in such detail.

"With the advent of the MERCI Retriever, we were finally able to systematically analyze blockages retrieved from live stroke victims within about six hours of symptom onset," said Dr. Sidney Starkman, professor of emergency medicine and neurology at the David Geffen School of Medicine at UCLA and co-director of the UCLA Stroke Center. "In the past, clots were studied from stroke victims who had died, and those clots were weeks, even months, old."

Ischemic stroke is the most common form of stroke and is the result of the blockage of a blood vessel feeding the brain. The blockages are typically clots that form in a heart or a neck artery, break off and travel to a recipient artery in the brain. The area of the brain not able to get its blood supply is injured from the lack of blood flow. The brain-damaged region is not able to do what it normally does, resulting in the signs and symptoms of stroke -- paralysis, difficulty speaking and difficulty seeing, among others.

The MERCI Retriever was invented at UCLA and sponsored by Concentric Medical of Mountain View, Calif. The Federal Drug Administration approved the MERCI Retriever in 2004 for removal of clots from brain arteries in patients experiencing ischemic stroke, within the first eight hours of stroke onset.