Feb. 5, 2004 (San Diego) — Results of phase I/II trials of a mechanical thrombectomy device suggest that mechanical retrieval of clots is a safe and effective treatment for ischemic stroke, which can extend the treatment window to as long as eight hours, according to results presented here at the 29th International Stroke Conference.
Sidney Starkman, MD, professor of emergency medicine and neurology at the University of California, Los Angeles, told Medscape that the device has some advantages over tissue plasminogen activator (tPA), the only Food and Drug Administration–approved treatment for ischemic stroke.
"Infusion of tPA takes two hours, whereas the device can retrieve clots within minutes," he said. Moreover, while the treatment window for tPA is three hours for standard infusion and six hours for intra-arterial delivery, it appears that this treatment can be performed up to eight hours after stroke onset," he said. He explained that that the eight-hour window was arrived at by "calculating the six-hour window for intra-arterial tPA, plus two hours' infusion time."
One hundred and forty-one patients were recruited for the studies presented here, and Dr. Starkman presented results on 114 in whom the Concentric Merci Retrieval System was used. "In 61 of these patients we achieved successful recanalization as measured by TIMI grade II or III," he said.
Moreover, in some patients the results were striking, he said: "We had patients who showed improvement on the table. It is not very often that we have the opportunity to see results that quickly."
Twenty-three of the 61 patients in whom retrieval was successful have "no disability or very minor disability," he said.
Dr. Starkman noted that even years after tPA was approved many "physicians, even many neurologists, are wary about using it because of the significant risk of bleeding." He said, however, that it may be possible to use the retrieval device "in combination with tPA, which will allow us to use much lower doses of tPA and thus significantly reduce risk." The current study excluded all patients who were eligible for tPA, but he said future studies will explore this combined approach.
Marc R. Mayberg, MD, professor and chair of the department of neurosurgery at the Cleveland Clinic Foundation in Ohio, told Medscape that the Merci retriever and other mechanical devices "mean that we can treat a great many patients who are not good candidates for tPA." Included in that group are recent surgery patients "which is a huge group, especially the cardiovascular surgery patients," and patients who are receiving routine anticoagulation regimens.
Larry Goldstein, MD, professor of neurology and director of the Duke University Medical Center, cautioned that the device is not a cure-all for stroke. "First, you have to be able to see the clot," he told Medscape, and he estimated that only about half of ischemic stroke patients have clots that are visible on computed tomography–angiography. Moreover, even if the clot can be seen, "it has to be in a location where you can get at it," Dr. Goldstein said. Many clots are located in arteries that are not accessible by catheter technology.
Nonetheless, Dr. Mayberg said that with only about 3% of stroke patients actually getting needed tPA, other treatment options are clearly needed.
The device's manufacturer, Concentric Medical Inc. of Mountain View, California, is slated to bring the device to the Food and Drug Administration's Neurovascular Devices Advisory Panel on Feb. 23. Dr. Starkman said. A positive recommendation from the panel will likely speed device approval.
29th International Stroke Conference: Abstract 30. Presented Feb. 6, 2004.
Reviewed by Gary D. Vogin, MD
Medscape Medical News © 2004
Cite this: Peggy Peck. Emboli Retrieval Device Demonstrates Efficacy for Ischemic Stroke - Medscape - Feb 05, 2004.
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