The year 2004 has been a year of reinforcing the idea of treating ischemic stroke. Measures for recanalization per endovascular approach are again proved to be feasible in the brain vessels. In this issue of Stroke, Gobin et al report an unprecedented, promising phase I feasibility study of removing clots from occluded vessels by corkscrew Mechanical Embolus Removal in Cerebral Ischemia (Merci) Retrieval System.1 Treating ischemic stroke by embolectomy is not a new concept; however, until this year, the efficacy of the treatment is emerging and not too invasive.
Recently, the US Food and Drug Administration cleared the device for clot removing. Clot removing might be a reasonable way to treat the occluded brain vessels in practice, but the efficacy of treating acute ischemic stroke by this device is not yet unyielding; thus, the indication should be taken as pending approval. The requirements for approval of the efficacy might be as comparable to those applied to prourokinase from the Prolyse in Acute Cerebral Thromboembolism Trial (PROACT) II.2
Although IV recombinant tissue plasminogen activator has been available in many European and Asian countries since 2002, the short time window ruthlessly limited the treatment incidence. Prehospital delay has been more than enough.3 As shown in this study, limited to no patients had been treated in participating centers. Patients were additionally excluded if the arterial stenosis was proximal to the thrombus, in the opinion of the investigator. Either the number of patients screened or the number of the angiograms done before the 30 eligible patients had been enrolled were not studied. These statistics will help to support the generalization and the feasibility of this technique. Until those figures are obtainable, this device might have the prospect to show efficacy in the real world outside the IV thrombolysis.
The clot removing might not be too invasive. The balloon inflation for the control of anterograde blood flow might reduce the flow-induced shear stress and potential fragmentation of the thrombus, but the duration and the vessels injury should be cautiously adjusted.
There were 6 successful recanalized intra-arterial procedures out of 8 patients among 14 patients with unsuccessful clot retrieval. This indicates that intra-arterial thrombolysis procedures, with the data granted by PROACT II, might help to back up the clots removing, left at the discretion of the interventionalist.
As in 2000, emergency cerebral angiography is out of the question in most hospitals. Thrombolysis In Myocardial Infarction (TIMI) grading is not a common language among stroke experts. There is a need for uniform definitions of collateral flow, degree of recanalization, assessment of perfusion, and infarct size to be applied in trials (such as phase 1 MERCI) to avoid confusing vascular analysis from the local principle investigators. Again, this is the time to take the great “technological leap” and incorporate vascular testing into the routine assessment of acute ischemic stroke.4
Though not perfect, the noninvasive evaluation of patients with suspected intracranial artery stenosis or occlusion might be available soon.5 But the attempts of adapting these measures in acute stroke treatment have rarely been met. Future studies concerning avoidance of the negative cerebral angiograms are warranted, such as using MRI, computed tomographic angiograms, or transcranial Doppler in the screening phase. Although the National Institutes of Health Stroke Scale could serve as a useful tool, the evidence to prove the occlusion in order to initiate the invasive treatment is crucial.
Although the desmoteplase thrombolysis selected by MRI perfusion/diffusion mismatch and intracranial stenting6 showed potential in 2004, the expenditure of these great technological leaps is sobering. The cost of the treatment in the few hours after stroke might be more than the amount for whole short-term hospitalization in certain welfare areas.7 Although with the benefits, the phase 2 MERCI study with 141 patients will struggle to support the use of this device outside the current participating centers. The estimates of effectiveness and cost-effectiveness of the device would be difficult or imprecise but desirable. With the estimates at hand and affirmative, the device would be really a mercy to victims of cerebrovascular diseases.
Gobin YP, Starkman S, Duckwiler GR, Grobelny T, Kidwell CS, Jahan R, Pile-Spellman J, Segal A, Vinuela F, Saver JL. MERCI 1: a phase 1 study of mechanical embolus removal in cerebral ischemia. Stroke. 2004; 35: 2848–2854.
Furlan AJ, Higashida R, Wechsler L, Gent M, Rowley H, Kase C, Pessin M, Ahuja A, Callahan F, Clark WM, Silver F, Rivera F, for the PROACT Investigators. Intra-arterial prourokinase for acute ischemic stroke: the PROACT II study: a randomized controlled trial. JAMA. 1999; 282: 2003–2011.
Chang KC, Tseng MC, Tan TY. Prehospital delay after acute stroke in Kaohsiung, Taiwan. Stroke,. 2004; 35: 700–704.
Furlan AJ. CVA: reducing the risk of a confused vascular analysis. The Feinberg Lecture. Stroke. 2000; 31: 1451–1456.
Jiang WJ, Wang YJ, Du B, Wang SX, Wang GH, Jin M, Dai JP. Stenting of symptomatic M1 stenosis of middle cerebral artery: an initial experience of 40 patients. Stroke. 2004; 35: 1375–1380.