OAHU, HAWAII — Mechanical embolectomy with the Merci retrieval system successfully restored vascular patency in 70% of patients with acute ischemic stroke caused by heretofore difficult-to-reach occlusions in the carotid terminus, Ronald F. Budzik Jr., M.D., said at a meeting sponsored by the American Society of Interventional and Therapeutic Neuroradiology.
Recanalized patients had significantly better neurologic outcomes than nonrecanalized patients, said Dr. Budzik, a neuroradiologist and codirector of interventional neuroradiology at Riverside Methodist Hospital, Columbus, Ohio.
Attempts to treat occlusions of the terminal internal carotid artery bifurcation with intravenous or intraarterial thrombolytics, such as alteplase or urokinase, have been ineffective, as evidenced by low mean recanalization rates, poor neurologic outcomes, and significant mortality after treatment failure. “These poor results have prompted clinicians to try alternative strategies,” said Dr. Budzik, who is a consultant to Concentric Medical Inc., which makes the Merci retrieval system.
Dr. Budzik retrospectively analyzed the data from 20 patients with carotid terminus lesions in the MERCI (Mechanical Embolus Removal in Cerebral Ischemia) trial. The trial investigated the safety and efficacy of the Merci retriever for opening occluded intracranial large vessels within 8 hours of the onset of stroke symptoms in a prospective, nonrandomized, multicenter trial. Safety and efficacy results of the trial have recently been published. (See box.)
Twelve patients with carotid terminus lesions (60%) were successfully recanalized following clot retrieval alone, and 14 patients (70%) achieved vascular patency when adjunctive therapies were added. Successful recanalization was defined as final Thrombolysis in Myocardial Infarction (TIMI) grade 2 or 3 flow in all treatable vessels (internal carotid artery, terminus of the internal carotid artery, and middle cerebral arteries 1 and 2).
Revascularization was clearly associated with good neurologic outcome, said Dr. Budzik. When patients were stratified according to whether recanalization was successful, 64% of those who achieved vascular patency had modified Rankin scale scores of 0–3 at 90 days, compared with 0% of those who did not (P = .03). When good neurologic outcome was defined as modified Rankin scale scores of 0–2, a similar trend was seen between recanalized and nonrecanalized patients (43% vs. 0%, respectively, P = .16).
Alternatively, failure to recanalize had serious consequences. While the overall mortality rate for the group at 90 days was 50%, mortality rates were higher among patients who could not be recanalized, compared with those who could (83% vs. 36%, respectively, P = .15). For example, a 65-year-old man presented with severe clinical symptoms (National Institutes of Health Stroke Scale [NIHSS] score of 20) 61/2 hours after symptom onset. Angiography showed the lesion was localized to the internal carotid terminus. After two passes with the X5 model of the Merci retriever, a 3-cm clot was removed and patency was restored.
Dr. Budzik, who is a member of a dedicated stroke center, said that triage is critical for rapidly determining which patients are eligible for embolectomy, antithrombolytic therapy, stenting, or other procedures. Candidates for clot retrieval should have a CT scan that is negative for hemorrhage or infarction, an NIHSS score of at least 8, and symptom duration of less than 8 hours. Those with symptoms for more than 8 hours may be eligible if they have severe stroke symptoms but no established evidence of stroke. Embolectomy patients often present after the 3-hour tissue plasminogen activator time window or are otherwise ineligible for intravenous tissue plasminogen activator. “Mechanical embolectomy is the treatment of choice for stroke caused by internal carotid terminus lesions,” said Dr. Budzik. “These are very bad strokes with high mortality rates of 40%–65% without treatment.”
MERCI Trial
The MERCI trial included 141 patients with intracranial occlusions who underwent mechanical embolectomy between 2001 and 2003 using the X5 and X6 first-generation Merci Retriever devices (Stroke 2005;36:1432–8). These devices received Food and Drug Administration approval in August 2004 for removing clots from the cerebral artery in patients with stroke. Results of the more recent Multi-MERCI trial, which utilized the LX/L5 and LX/L6 second-generation Merci devices, have not yet been published. The LX/L5, a single-use device, has been approved by the FDA as a foreign-body retriever, and the LX/L6 has been submitted for approval.