Published online before print June 4, 2009, doi: 10.1161/STROKEAHA.109.552893
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(Stroke. 2009;40:2910.)
© 2009 American Heart Association, Inc.
Controversies in Stroke |
MR Mismatch and Thrombolysis
Appealing but Validation Required
From the Department of Neurology, Royal Melbourne Hospital, Parkville Vic Australia.
Correspondence to Professor Stephen Davis, Divisional Director of Neurosciences, Director of Neurology, Royal Melbourne Hospital, Parkville Vic Australia 3050. E-mail linda.foottit@mh.org.au
Key Words: diffusion-weighted imaging • thrombolysis • MR mismatch • controversies
An extract of the first 250 words of the full text is provided, because this article has no abstract. |
Since the initial description of the ischemic penumbra 30 years ago, the concept of rapid restoration of blood flow to threatened brain tissue has been the "holy grail" of acute stroke therapy.1,2 Despite its drawbacks, MR imaging of perfusion diffusion mismatch remains the most widely used and practical means of in vivo assessment.
There is accumulating evidence linking reperfusion with better clinical outcomes and attenuation of infarct growth in patients in patients with MR mismatch. However, validation that imaging effectively selects thrombolytic responders is still lacking. Both protagonists have highlighted areas of uncertainty in definition of MR mismatch. In our view, these include optimizing the ratio between PWI and DWI, choice of metric (we find Tmax, the time to peak of residue function, most useful), and choice of threshold to exclude benign oligemia (Tmax 4 to 6 appears to be better than Tmax 2).3,4 Another key question is the option of excluding large DWI volumes to reduce the risk of hemorrhagic transformation and poor outcome with thrombolysis. We consider that baseline core infarct volumes of >100 mL on DWI should be excluded.5,6
As mentioned by both protagonists, there have been 3 key trials that have addressed the question of MR mismatch and thrombolysis, namely DEFUSE,6 EPITHET,7 and ECASS III.8 The former 2 provided biological evidence to support a strong relationship between reperfusion, attenuation of infarct growth, and improved clinical outcomes. Indeed in EPITHET, tPA significantly enhanced reperfusion in the 3- to 6-hour time window. Although neither EPITHET nor DEFUSE selected
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