The Three Hour Window for tPA Stroke Treatment

Stroke treatment has undergone a number of significant advances, and the most important of these is still believed to be the use of a medication called Tissue Plasminogen Activator (tPA) for stroke.

What is tPA?

In the 1990's, medical researchers began using tPA, a powerful blood thinner, for the treatment of ischemic stroke. Over 80% of all strokes are ischemic, which means that they are caused by blood clots that interrupt blood flow in an area of the brain.

Treatment with tPA acts by dissolving these stroke-causing blood clots. This is particularly urgent during a stroke because ischemia, which is the lack of blood supply, rapidly causes a series of toxic chemical reactions that produce brain damage. And effective treatment with tPA can permit blood to flow to the affected area of the brain, with the goal of preventing the permanent brain damage that is caused by ischemia.

When Can You Receive tPA treatment?

The effectiveness of tPA for stroke treatment has been proven through several large clinical trials which show a greater chance of recovery among stroke patients who are treated with tPA when compared with stroke patients who are not treated with tPA.

However, these trials also show that if tPA is given later than three hours after a person first begins to experience stroke symptoms, the treatment can cause dangerous bleeding in the brain, causing a hemorrhagic stroke.

Therefore, while tPA is a life saving treatment in some situations, it can cause serious complications, making the stroke even worse than it would have been without tPA. Consequently, it is only safe to receive treatment with tPA within 3 hours of the beginning of stroke symptoms. This is what is considered to be the "golden three hour tPA window" for stroke treatment.

It is also important to know that not every stroke patient who arrives to the emergency room within 3 hours of stroke onset is automatically treated with tPA. There are a variety of other situations and conditions that make it unsafe to receive treatment with tPA, including several blood disorders and heart conditions.

Why Do Some Stroke Patients Miss the Three Hour Window?

Unfortunately, the 3 hour window is often missed because it can be difficult for people to get to the hospital within 3 hours of the start of a stroke. There are a variety of causes for the delay in emergency treatment.

  • Not recognizing a stroke

If a person or those who are around him or her does not recognize symptoms of a stroke, then they may not seek help.

  • Losing consciousness

If the stroke symptoms are so severe that they make it impossible to call for help, it may take more than 3 hours to get medical attention for a stroke.

  • Waiting for a friend/family member opinion

Often people who are experiencing a stroke wait for a friend or family member to help them decide if the problem is serious enough to warrant medical attention.

  • Want a friend/family member to accompany to hospital

And, many stroke sufferers want a loved one to take them to the hospital, instead of calling 911 for immediate help.

Because of these and other factors, only a small fraction of stroke patients arrive at the hospital in time to receive treatment with tPA.

Faster Treatment

A new way of getting to the hospital sooner for tPA treatment is called the Mobile Stroke Unit. Started in Germany, Mobile Stroke Units have been adopted in Houston, Texas and Cleveland, Ohio as a way to get stroke patients evaluated while they are still on the way to the hospital. This may help more patients get tPA within the 3 hour window.

A Word From Verywell

Perhaps the most common cause of delay in getting tPA is the lack of awareness about stroke signs and symptoms.

Most people wait up to a day after their symptoms start before seeking medical attention because they simply don't recognize that their symptoms are those of a stroke.

You can learn how to recognize the symptoms of a stroke in case you ever personally experience a stroke, or in case you are ever nearby at the time that someone else experiences a stroke.


Strategies to Extend Thrombolytic Time Window for Ischemic Stroke Treatment: An Unmet Clinical Need.Peña ID, Borlongan C, Shen G, Davis W, J Stroke. 2017 Jan;19(1):50-60