News

Study finds wider time window for clot-busting drugs may benefit stroke patients

July 27, 2010

By Patricia Nicholson

New research supports widening the treatment window for thrombolytic drugs – or ‘clot-busters’ – in stroke patients from three hours to 4.5 hours after symptoms begin. However, the faster the drugs are administered, the safer and more effective they are.

Thrombolytics are the only approved treatment for acute ischemic stroke, and they are quite effective. However, many guidelines (including Health Canada’s) dictate that they must be used within three hours of the onset of stroke symptoms, so they often cannot be used if a patient arrives at the hospital too late. It also means that fast diagnosis and treatment at the hospital is crucial.

Ischemic strokes are usually caused by blood clots blocking a blood vessel, preventing blood from reaching the brain. Thrombolytic drugs are often called clot-busters because they break up the blood clot, help remove the blockage and re-establish blood flow to the brain.

After observational research released in 2008 suggested that a 4.5-hour treatment window might be safe for thrombolytics, European stroke organizations changed their guidelines to expand the window. The current study examines whether this expansion had any benefit, and also investigates whether it increased health risks such as brain hemorrhages, or affected the overall speed of treatment for stoke patients.

The study included 23,972 stroke patients treated in Europe, Asia and Australia between 2002 and 2010. About 10 per cent (2,376) were treated between three and 4.5 hours after their symptoms began.

The researchers found that late thrombolytic treatment of stroke (after three hours) was implemented quickly after 2008. However, the number of patients treated rapidly (under three hours) also increased during this time. There was no difference in the average time it took to administer clot-busters to stroke patients after they arrived at the hospital.

The patients treated after three hours did have an increased risk of brain hemorrhage within three months of treatment, compared to patients treated within the original three-hour window. Late-treated patients were also more likely to die and less likely to be functionally independent within three months, compared to patients treated more quickly. However, the researchers noted that the increased risks were small, and were outweighed by the benefits of treatment.

Expanding the time window enabled the treatment of a significant number of stroke patients who would otherwise not have received clot-busting therapy. However, time-to-treatment remains a crucial factor for stroke patients.

The study findings suggest that using thrombolytics up to 4.5 hours after a stroke could enable doctors to treat stroke patients who otherwise would not get clot-busters, but that earlier treatment is preferable because effectiveness and safety decrease after three hours.

The research was published online in Lancet Neurology on July 27, 2010.

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