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Stroke Treatment Gets Boost From New Clot Retrievers

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Trials Are Major Steps Forward

Despite modest sample sizes, the "carefully done" SWIFT and TREVO 2 trials begin to answer the call for high-level evidence about the efficacy and safety of mechanical clot retrieval devices in acute ischemic stroke, Dr. Philip B. Gorelick wrote in an editorial accompanying the Lancet articles.

"It will be interesting to learn, on the basis of future non-primary analyses, whether collateral flow patterns or clot characteristics elucidate propensity for treatment response," he said (Lancet 2012 Aug. 26 [doi: 10.1016/S0140-6736(12)61302-6]).

He also stated that the "mechanistic basis for superiority" of these next-generation devices might relate to retention of structural integrity of the clot and vessel wall during the procedure.

"Future randomized trials of these and other, newer devices will need to take into account comparison or complementary treatment with rt-PA [recombinant tissue plasminogen activator], or with newer-generation thrombolytics such as desmoteplase and tenecteplase," he said.

Meanwhile, SWIFT and TREVO 2 represent major steps forward, and pave the way for new treatment options, as well as for further validation by additional study, he said.

Dr. Gorelick is with the Hauenstein Neuroscience Center and Michigan State University College of Human Medicine in Grand Rapids. He disclosed that he receives remuneration as co-director of the clinical coordinating center for the DIAS trial that involves desmoteplase.



Two novel "next generation" mechanical flow restoration devices, or "clot retrievers," show promise for improving the treatment of stroke patients who fail or aren’t eligible for treatment with tissue plasminogen activator, according to findings from separate randomized controlled clinical trials.

In the SWIFT (Solitaire With the Intention of Thrombectomy) trial, the new Solitaire flow restoration device, a self-expanding stent retriever designed to restore blood flow in patients with ischemic stroke due to a large intracranial vessel occlusion, proved significantly more likely to successfully recanalize occlusions of the proximal cerebral arteries than did the Merci retriever, a first-generation mechanical thrombectomy device approved for use in 2004. The results showed that 58 patients treated with the Solitaire device had nearly fivefold greater odds of meeting the primary end point of a Thrombolysis in Myocardial Ischemia (TIMI) scale 2 or 3 flow in all treatable vessels than did 55 patients treated with the Merci retriever (61% vs. 24%; odds ratio, 4.87).

In another trial called TREVO 2, 88 patients treated with the new Trevo Retriever, a stentlike device similar to the Solitaire device, had greater than fourfold higher odds of successful revascularization than did 90 patients treated with the Merci retriever (86% vs. 60%; OR, 4.22). This trial used a slightly different definition of successful recanalization than did the SWIFT trial, defining it as a Thrombolysis in Cerebral Infarction (TICI) score of 2 or greater.

The findings of both trials were published Aug. 26 in the Lancet and were simultaneously presented at the annual congress of the European Society of Cardiology.

Dr. Jeffrey L. Saver

Dr. Jeffrey L. Saver of the University of California, Los Angeles, and his colleagues enrolled patients in the SWIFT trial at 18 sites between February 2010 and February 2011, if they had acute ischemic stroke with moderate to severe neurological deficits and angiographically confirmed occlusions of the proximal cerebral arteries, that were treatable by thrombectomy within 8 hours of symptom onset.

In addition to the greater likelihood of achieving the primary end point, the Solitaire patients were more likely to have good 90-day neurological outcomes (58% vs. 33%; OR, 2.78), and to require fewer passes with the device (mean of 1.7 vs. 2.2 passes), the investigators said (Lancet 2012 Aug. 26 [doi: 10.1016/S0140-6736(12)61384-1]).

Furthermore, the frequency of total device-related and procedure-related adverse events did not differ between the two groups, and the 90-day mortality rate was lower in the Solitaire group (OR, 0.29 after adjusting for age and time to treatment), the investigators said.

"On the basis of these results, when endovascular recanalization is done in patients with acute ischemic stroke, initial treatment with Solitaire might be a future treatment of choice," they concluded.

Dr. Raul G. Nogueira of Emory University in Atlanta and his colleagues enrolled patients in the TREVO 2 trial at 26 sites between February 2011 and December 2011, if they had acute onset of stroke symptoms leading to significant clinical deficits, angiographically proven occlusion of a proximal intracranial artery, and eligibility for endovascular therapy within 8 hours of symptom onset.

Dr. Raul G. Nogueira

In addition to the greater likelihood of achieving the primary end point, the Trevo patients were less likely to require adjunctive treatment of any kind (18% vs. 31%; OR, 0.49), and after adjunctive interventions, the rate of TICI 2 or greater reperfusion was higher in the Trevo patients, the investigators said (Lancet 2012 Aug. 26 [doi: 10.1016/S0140-6736(12)61299-9]).

The Trevo patients also were more likely to have good 90-day functional outcomes (40% vs. 22%; OR, 2.39).

No significant differences were seen between the Trevo and Merci patients with respect to the primary safety end point (a composite of multiple device- and procedure-related events), although vessel perforations were 10 times more common with the Merci device, the investigators reported.

Mortality was also similar in both groups at 30 and 90 days.

The investigators noted that although the Trevo device was not compared with medical treatment alone in this study, the findings are encouraging when considered in the context of those from studies of the Trevo predecessor – PROACT II. In the current study, patients treated using the Trevo Retriever achieved the same rate of good clinical outcomes as reported in a pro-urokinase group in the PROACT II trial despite older age, higher baseline National Institutes of Health Stroke Scale score, more proximal occlusions, and more refractory occlusions.

"Our results are therefore encouraging and support the use of the Trevo Retriever in a prospective randomized trial of endovascular therapy against medical treatment alone," the investigators concluded.


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