SAN FRANCISCO — Recanalization rates are higher and mortality is lower in stroke patients who undergo intracranial clot retrieval with the newest generation Mechanical Embolus Removal in Cerebral Ischemia (Merci) retriever, compared with prior versions of the device, according to final trial results.
The newer (L5) version of the Merci device, which “has an arcade of monofilaments that attach both distally and proximally to better ensnare the clot,” also appears to be associated with a low symptomatic intracerebral hemorrhage rate, Dr. Wade Smith reported at the 32nd International Stroke Conference.
The Multi MERCI trial was a prospective, 15-center, single-arm trial of patients with acute large-vessel stroke associated with vertebral, basilar, intracranial carotid, or M1 and M2 occlusions.
A total of 164 patients who were either ineligible for intravenous tissue plasminogen activator (TPA) or who underwent IV TPA but did not recanalize were enrolled and underwent clot retrieval within 8 hours of onset, with a mean of 4 hours from symptom onset to groin puncture for the catheter-based procedure, said Dr. Smith, a professor of neurology at the University of California, San Francisco.
The L5 device was used in 131 patients, either exclusively or followed by subsequent passes with the first-generation X5 or X6 devices, which were previously evaluated in the 141-patient MERCI trial; the X5 or X6 versions were used exclusively in the first 33 patients enrolled in the Multi MERCI trial, which was sponsored by Concentric Medical Inc., the device's maker.
Primary outcomes included a device-only recanalization rate of 55%, a final (device plus adjuvant therapy) recanalization rate of 68%, and a final L5 plus adjuvant therapy revascularization rate of 70%.
Clinically significant procedure-related complications occurred in nine (7%) patients, and one patient experienced a nonclinically significant device-related complication, said Dr. Smith, who owns stock in Concentric Medical.
Results of part I of Multi MERCI, which were published last year, showed that the device along with use of IV TPA was safe; IV TPA was not allowed in the initial MERCI trial.
When outcomes in Multi MERCI were compared with those in patients who were recanalized and those who were not, good outcomes occurred in 49% vs. 10%, respectively, and mortality was 25% vs. 52%, respectively.
A comparison of results from Multi MERCI and MERCI showed that there was a trend toward improvement in device recanalization in Multi MERCI (55% vs. 48%), and in final recanalization (68% vs. 60%), Dr. Smith reported at the conference, which was sponsored by the American Stroke Association.
Mortality at 90 days was also improved in the Multi MERCI trial, compared with the MERCI trial (34% vs. 44%), and there was a trend toward improved favorable outcomes, defined as a modified Rankin score of 2 or less (36% vs. 28%), he said.
Patients in the two studies had a similar mean age (68 and 67 years in Multi MERCI and MERCI, respectively), and similar mean National Institutes of Health Stroke Scale scores (19 and 20, respectively).
Although the differences in outcomes between the new L5 device and the first-generation devices as demonstrated in the Multi MERCI and MERCI trials did not reach statistical significance, they are “definitely in the right direction,” Dr. Smith said.
Randomized trials will be needed to confirm an association between the Merci devices and improved outcomes and mortality in stroke patients, but the higher rate of favorable outcomes and the lower mortality in Multi MERCI, compared with MERCI, are likely a result of the improved recanalization rate seen with the new generation device, and possibly with increased experience with the Merci systems, he said.
Also of note is the low (2.4%) clinically relevant intracerebral hemorrhage (parenchymal hemorrhage type 2) rate identified in Multi MERCI by two blinded investigators, he said, noting that this “exciting finding” suggests that thrombectomy is safer than TPA, which has been associated with higher rates of intracerebral hemorrhage.
The first-generation Merci devices were approved by the Food and Drug Administration in 2004. Concentric Medicine announced in February that the L5 device had also received clearance for commercial release.
FULL TEXT
