The Three Hour Window for tPA Stroke Treatment

Artwork of cerebral embolism, cause of stroke


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

How tPA Works

In the 1990s, physicians 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 prevents stroke-causing blood clots from growing. 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 You 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 survivors who have been treated with tPA when compared with those who were not treated with tPA.

These trials have also shown 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 considered safe to receive treatment with tPA within 3 hours of the beginning of stroke symptoms.

Recent research is focused on the possibility of expanding the 3-hour window by identifying certain criteria that may make it safe for someone who is having a stroke to receive tPA even after the 3-hour window. 

Not Every Person Can Receive tPA Even in the 3 Hour Window

It is also important to know that even if you arrive to an emergency room within 3 hours of stroke onset, you might not receive treatment with tPA. There are a variety of situations and conditions that make it unsafe to receive treatment with tPA, including having a hemorrhagic stroke, a brain aneurysm, or a blood disorder.

Why You Might 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's 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: 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 people who experience a stroke arrive at the hospital in time to receive treatment with tPA.

Faster Stroke 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 a few cities worldwide as a way to get people who are having a stroke evaluated while they are still on the way to the hospital. This process may eventually help more people receive 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 stroke symptoms begin 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 so that you can be ready if you ever personally experience a stroke, or if you are ever nearby at the time that someone else experiences a stroke.

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