In 1995 the clot dissolving drug tPA was first demonstrated to be effective in the treatment of the most common type of stroke, those caused by blood clots plugging arteries in the brain. Since that time, no newer therapy has been proven to improve the outcome of stroke patients compared to tPA. But tPA treatment is limited, as it must be initiated very early following the onset of stroke (in the US, FDA approval is for use up to 3 hours, although it is in widespread use up to 4.5 hours in selected patients and around the world), and it may not be effective in opening clots in larger arteries that are responsible for the most severe strokes.
For roughly the past 10 years, advanced stroke centers have utilized a type of therapy known as interventional, or endovascular. This type of therapy uses a catheter to place a device into an artery in the brain to remove the clot responsible for the stroke. Although stroke specialists had hoped that these techniques would prove more effective in some patients, no clinical studies have been able to demonstrate that interventional therapy in addition to tPA was more effective than intravenous tPA alone.
The winds of change may be blowing, however. A new clinical study which compared tPA with endovascular therapy following tPA treatment, performed in the Netherlands and recently published in the New England Journal of Medicine, demonstrated improved outcomes for those patients that received endovascular therapy. This is the first study to validate the use of endovascular therapy in patients with severe strokes.
Why was this study positive, in distinction to the previous negative ones? Examining the reasons for success give the direction of future stroke therapy. The investigators used more advanced types of CT scans to select patients with large blood clots blocking major arteries, choosing patients thought to be most appropriate for intervention. And there were two other vitally important differences. Patients were treated sooner than in the previous studies, and a newer generation of instruments and devices were used to open the clogged arteries. These newer devices have been shown to be more effective at removing clots.
Does this mean that stroke therapy is about to undergo the type of change it experienced when tPA was introduced in 1996? Not just yet. This was only one clinical study, performed on a carefully selected group of stroke patients. Information from additional studies will be required to better understand the factors that lead to successful endovascular therapy of stroke. This information will be forthcoming within the next few months. And then it will be up to our hospitals and EMS systems to move forward and advance stroke treatment.
Stay tuned. We will keep you up to date on the major advances in stroke treatment and prevention.