Selection of thrombolytic therapy beyond 3 h using magnetic resonance imaging

Curr Opin Neurol. 2005 Feb;18(1):47-52. doi: 10.1097/00019052-200502000-00010.


Purpose of review: Use of intravenous thrombolytic therapy in ischaemic stroke is restricted to a 3-h time window because of the proof of this time window in pivotal clinical trials. Thrombolysis is aimed at recanalization of occluded arteries and reperfusion of the ischaemic penumbra, a region of critically hypoperfused, functionally impaired, but potentially viable brain. There are a number of current prospective trials that are testing the hypothesis that the presence of the penumbra will predict thrombolytic responders beyond 3 h.

Recent findings: Using magnetic resonance imaging, a mismatch between a larger perfusion-weighted imaging lesion and smaller diffusion-weighted imaging lesion is considered to represent the ischaemic penumbra. Perfusion-weighted imaging provides semiquantitative cerebral blood flow imaging and diffusion-weighted imaging is an index of the largely irreversible ischaemic core. This definition has been modified with the recognition that the perfusion-weighted imaging lesion includes benign oligaemia and that a portion of the diffusion-weighted imaging core is potentially salvageable with rapid reperfusion. Most acute stroke patients have a magnetic resonance imaging-penumbral signature within 6 h of stroke onset. The penumbra is commonly, but not invariably, associated with proximal arterial occlusion and is time-dependent. Preliminary studies have shown benefit from thrombolytic therapy beyond the established 3-h window.

Summary: Penumbral imaging using magnetic resonance imaging with perfusion over diffusion weighted imaging mismatch can provide a physiological 'tissue clock' in individual patients. Based on this hypothesis, a number of prospective trials are being performed. These include EPITHET, DEFUSE, DIAS, MR RESCUE and ROSIE.

Publication types

  • Review

MeSH terms

  • Brain / pathology
  • Cerebrovascular Circulation
  • Clinical Trials as Topic
  • Evaluation Studies as Topic
  • Fibrinolytic Agents / therapeutic use*
  • Humans
  • Magnetic Resonance Imaging*
  • Stroke / drug therapy*
  • Stroke / pathology*
  • Time Factors


  • Fibrinolytic Agents