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30-10-2011 | Stroke | Article

Baseline arterial obstruction predicts tPA response

Abstract

Free abstract

MedWire News: Stroke patients with arterial obstruction on baseline magnetic resonance angiography (MRA) have a better response to intravenous thrombolysis than those with no such obstruction, a post hoc analysis of clinical trial data indicates.

The study authors say this supports the use of baseline arterial obstruction status when considering whether patients are likely to benefit from treatment with intravenous tissue plasminogen activator (tPA).

Deidre De Silva (Singapore General Hospital) and colleagues obtained information on 175 participants in the EPITHET (EchoPlanar Imaging THrombolytic Evaluation Trial) and DEFUSE (Diffusion and perfusion imaging Evaluation For Understanding Stroke Evolution) studies.

All patients had ischemic stroke and received either tPA or placebo within 3-6 hours of symptom onset. The primary efficacy measure, infarct growth, was defined as the difference between baseline diffusion-weighted imaging (DWI) and final T2 lesion volumes.

Among 116 patients with evaluable data, 72 had baseline arterial obstruction of the large intracranial arteries while 44 had no arterial obstruction.

Importantly, in patients with arterial obstruction, infarct growth was significantly lower in patients treated with tPA than those given placebo, with a median difference of 26 mL.

By contrast, in patients without arterial obstruction, there was little difference in infarct growth between the tPA and placebo groups (median difference 5 mL).

Futhermore, the attenuation of infarct growth in response to tPA treatment was 32 mL greater in patients with versus those without arterial obstruction. This remained significant, with a median difference of 33 mL, after adjustment for age.

Overall, however, patients without obstruction fared better after stroke. Among those without obstruction, 66% of the tPA group had a good functional outcome at 90 days (defined as a modified Rankin score of 0-2) versus 42% of the placebo group, giving an odds ratio (OR) of 2.69.

Among patients with arterial obstruction, 43% of the tPA group had a good functional outcome versus 34% of the placebo group, giving an OR of 1.44.

Discussing their results, the authors note that that the presence of arterial obstruction "does not equate to that of an ischemic penumbra," citing the fact that 16% of patients with arterial obstruction did not have a mismatch profile.

"Arterial obstruction may occur without any corresponding tissue hypoperfusion due to alternative arterial supply via collaterals and communicating arteries, early completed infarct growth into the ischemic penumbra, or recanalization of a tandem arterial obstruction," they explain. "On the other hand, tissue hypoperfusion may be evident despite no obstruction of large arteries."

They conclude: "Arterial obstruction status might provide additional or complementary information in treatment selection for IV tPA, particularly in the wider time windows."

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Joanna Lyford