According to the American Heart Association, the tPA window can be expanded up to how many hours?

• A. 3 hours
• B. 4.5 hours
• C. 6 hours
• D. 12 hours

Answer: (B)

The main idea is how long after stroke onset you can still give IV alteplase (tPA) safely. The standard window is within a few hours, but the American Heart Association allows extending the window to four and a half hours for select patients, based on trials like ECASS III that showed a net functional benefit in that extended timeframe when patients meet specific exclusion criteria and imaging confirms no bleed. This expanded window isn’t automatic for everyone—there are stricter screening rules and imaging requirements to minimize the risk of hemorrhage. So, the window can be expanded up to four and a half hours.