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Mechanical Clot Retrieval in the Treatment of Acute Ischemic Stroke

2013; Lippincott Williams & Wilkins; Volume: 72; Issue: 2 Linguagem: Inglês

10.1227/01.neu.0000426217.97583.1b

1524-4040

Robert M. Starke, Ricardo J. Komotar, E. Sander Connolly,

Stroke Rehabilitation and Recovery

Proximal occlusion of intracranial arteries is a common cause of ischemic stroke, leading to significant morbidity and mortality.1,2 Currently approved managements for patients with ischemic stroke include supportive care in a stroke unit or center, use of aspirin to prevent clot propagation, revascularization with recombinant tissue plasminogen activator (tPA) until 4.5 hours after onset, intraarterial fibrinolysis until 6 hours, and mechanical thrombectomy until 8 hours.3 Significant controversy surrounds the use of mechanical thrombectomy as improved recanalization rates may not be associated with increased favorable outcome. The Interventional Management of Stroke III trial was recently stopped early as interim analysis demonstrated that a clinically significant difference was unlikely between patients treated with tPA alone or tPA along with either intra-arterial tPA or mechanical thrombectomy.4 A recent analysis of thrombectomy studies in acute ischemic stroke found little evidence to support their use in daily clinical practice and randomized clinical trials would be necessary to further define appropriate treatment algorithms and instruments.5 Lack of supportive evidence lead to the American College of Chest Physicians' 2012 guidelines which recommended against the use of mechanical thrombectomy for ischemic stroke.6 Due to the side effect profile as well as limitations in efficacy and time-frame of current treatment options, researchers have looked towards alternate revascularization treatments. Most recently, 2 randomized clinical trials have compared newer clot retrieval devices in the treatment of acute ischemic stroke.7,8 In the Solitaire flow restoration device vs the Merci Retriever in patients with acute ischaemic stroke (SWIFT), patients with moderate to severe neurological deficits with proximal intracranial cerebral artery occlusion who were ineligible or failed to respond to tPA were randomized to treatment with the Solitaire or Merci devices.7 The trial was stopped at interim analysis as patients were significantly more likely to have flow restoration (Thrombolysis In Myocardial Ischemia scale 2 or 3) and without symptomatic intracranial hemorrhage following treatment with the Solitaire (64%) vs Merci (24%). Patients were also 2.78 times more likely favorable 3-month outcome following treatment with the Solitaire (58%) vs Merci (33%) and mortality within 3 months was also significantly reduced. In a similar clinical trial, patients with proximal intracranial artery occlusion and acute ischemic stroke failing or ineligible for treatment with tPA were randomized to thrombectomy with the Trevo Retreiver or Merci device.8 Those treated with the Trevo were 4.2 times more likely to achieve revascularization. Favorable 30-day outcome was also significantly higher in those treated with the Trevo (40%) vs Merci (22%). Overall serious complications in occurred both trials including 19% in the Swift trial. In the Trevo 2 study, there was a 10% rate of vessel perforation in patients treated with the Merci device. Radiographic hemorrhage occurred in 17% to 53% of patients with varied rates of symptomatic hemorrhage based on definition from 0 to 11% in various treatment arms. In these trials,7,8 less than 10% of patients had basilar or verterbral artery occlusion. Further studies in patients with posterior circulation thrombosis are indicated. The time frame for salvageable following basilar or vertebral artery thrombosis is unclear, but longer time periods may be possible.9,10 As such, attention towards these specific cohorts requires further assessment. Although these recent trials of clot retrival devices are promising, further long-term outcomes are needed to assess the overall benefit of these devices. In both trials using newer devices there was a conversion of patients from fatal outcomes to intermediate levels of disability rather that converting intermediate and worse outcomes to independence. This is consistent with a recent analysis of the National Inpatient Sample whereby approximately 4000 patients treated with mechanical thrombectomy, 75% died while in the hospital or were discharged to long-term care facilities.11 A wide variety factors are associated with response to mechanical clot retrieval and revascularization including specific patient characteristics as well as clot location and etiology, collateral blood flow and hemodynamic compromise, time until treatment, and quantify of brain ischemia.12,13 Future trials which are better able to identify which patients may respond to mechanical clot retrieval are a promising means of improved care in acute stroke patients. Newer imaging techniques may help predict which patients will benefit from thrombectomy.12,14 Additionally, these studies will have to take into account newer medical therapies including newer plasminogen and neuroprotective agents, which may be more effective.3 Although these trials provide a promising avenue of treatment for acute stroke patients with proximal intracranial occlusion, further studies are needed to determine to optimal treatment strategy. To definitively show a benefit of these treatments a randomized clinical trial is needed to compare modern mechanical thrombectomy with intravenous thrombolysis alone in patients eligible for tPA as well as a comparison of mechanical thrombectomy and supportive care in tPA ineligible patients.Figure: Example angiography and devices (A–H) Angiography images of a 67-year-old woman presenting with left hemiplegia and dysarthria (NIHSS 12). Intravenous recombinant tissue plasminogen activator was given 115 minutes after symptom onset without improvement. (A–B) Angiography before treatment showing complete occlusion of the M1 segment of the right MCA (arrows). (C–E) Angiography after deployment of the Trevo Retriever across the occluded segment showing a perfusion channel with contrast opacification of the distal MCA territory (arrowheads). Black arrows in panels C–E show the proximal Trevo markers and white arrows show the distal Trevo markers. (E) Magnified native image of panel C. (F–G) Angiography after treatment showing near complete reperfusion of the right MCA territory (TICI 2b). At 90 days, the patient's NIHSS was 0 and modified Rankin scale score was 1. (H) Trevo device and retrieved complex thromboembolic material. (I–J) Thrombus incorporation by the Trevo (I) and Merci (J) retrievers. NIHSS, National Institutes of Health Stroke Scale; MCA, middle cerebral artery; TICI, thrombolysis in cerebral infarction grading scale score. Courtesy of - Trevo vs Merci retrievers for thrombectomy revascularisation of large vessel occlusions in acute ischaemic stroke (TREVO 2): a randomised trial.