ACEP: Clot-Snaring Devices Improve Outcomes After Ischemic Stroke

October 16, 2006

NEW ORLEANS -- In acute ischemic stroke patients, mechanical snares and other devices that remove clots can improve survival and functional outcomes, investigators reported here.

NEW ORLEANS. Oct. 16 -- In acute ischemic stroke patients, mechanical snares and other devices that remove clots can improve survival and functional outcomes, investigators reported here.

In a meta-analysis of 22 studies with 147 stroke patients, those who did not undergo clot retrieval procedures had about twice the risk for death, a Mayo Clinic team reported at the American College of Emergency Physicians meeting here.

Patients who underwent the procedure were about seven to 14 times more likely to have a good score on the modified Rankin scale, reported Latha G. Stead, M.D., of Rochester, Minn., and colleagues.

The investigators did a systematic review of clot removal systems for acute ischemic stroke, including laser, rheolytic thrombectomy, aspiration, coil, snare, and ultrasound devices. They conducted a literature search, and got in touch with study authors to obtain missing data when necessary. They also conferred with device manufacturers for information.

They looked separately at procedures that were technical successes (meaning that the device could actually reach the clot) and at failures. They calculated odds ratios for mortality and functional outcome based on 90-day modified Rankin score, in which a score of 0 (no disability) to 2 (slight disability, with the patient unable to carry out all previous activities, but able to look after his/her own affairs without assistance) was considered to be a good score, and a score of 3 (moderate disability; requiring some help, but able to walk without assistance) to 6 (death) was considered a bad outcome.

They also looked at the rate of post-procedure hemorrhage as a secondary endpoint.

Dr. Stead and colleagues also compared the pooled cohort from the meta-analysis with the cohort of emergency department acute stroke cases at the Mayo.

To rule out the possibility that stroke severity could be driving the results, they identified 80 patients each in the pooled and Mayo cohorts and matched them by gender, age and National Institute of Health Stroke Scale (NIHSS) for subgroup analyses.

They found that the middle cerebral artery was occluded in 42% of all cases, followed by the posterior circulation vessels in 38%, and the internal carotid artery in 19%.

The mean time from symptom onset to mechanical interventions was 8.9 (median 5, standard deviation 21.6) hours. The clot was accessible in 86% of the cases, and at least partial recanalization was possible in 79%.

Broken down by TIMI (Thrombolysis in Myocardial Infarction) flow grade, 10% had grade 1 (minimal) flow, 23% had grade 2 (partial flow), and 46% had grade 3 (complete) flow.

"In only 4% of cases was recanalization achieved despite technical failure, and concurrent thrombolysis was used in these cases," the authors wrote in their poster presentation.

Hemorrhages, both symptomatic and asymptomatic, occurred in 22% of treated patients.

Among the 126 patients with accessible clots, 81 (65%) had poor outcome on the modified Rankin scale, compared with 18 of 21 patients (76%) with inaccessible clots (chi-square test, P=0.31).

The overall 90-day death rate was 31%. Among the patients with accessible clots, 37 (29%) died within the first three months of treatment, compared with eight patients (38%) with inaccessible clots (P=0.42).

Neither accessibility, technical or clinical success, nor the 90-day death rate were influenced by mechanical intervention type, concurrent thrombolytic therapy, or occurrence of hemorrhage.

Hemorrhages occurred in 18 of 66 patients (27.3%) who were not on concurrent thrombolytic therapy, compared with 15 of 81 (18.5%) of patients who were taking concurrent thrombolytic agents.

The authors found that patients who underwent a procedure with a snare device were significantly more likely to be more independent at 90 days compared to those operated on with other devices (P=0.03). Other factors associated with clinical success were younger age (P=0.001) and lower admission NIHSS (P

In multivariate logistic regression models of the pooled cohort adjusted for gender, age, and NIHSS score, the authors found that "patients who did have a procedure were 7.4 times more likely to have a good Rankin score (95% confidence interval, 3.7-14.7, P