Which time window is critical for initiating thrombolytic therapy in ischemic stroke?

• A. Within 4.5 hours
• B. Within 24 hours
• C. Within 72 hours
• D. Anytime during the day

Answer: (A)

The key idea is that thrombolytic therapy for ischemic stroke works best when given as soon as possible after symptoms start, because it dissolves the clot and helps salvage brain tissue that is at risk. Evidence from major trials shows that intravenous thrombolysis with rt-PA provides the most benefit when started within 4.5 hours of onset in eligible patients. Beyond this window, the chance of meaningful recovery diminishes and the risk of harmful bleeding increases, so this treatment is not routinely recommended. The other time frames listed either fall outside the proven window or aren’t applicable to thrombolysis. So, the critical window to initiate thrombolytic therapy is within 4.5 hours of symptom onset.