What is rescue therapy in regards to stroke, and who qualifies for this?

Aspirin and tPA (alteplase) At the first sign of stroke immediately take 325 mg of Aspirin (unless allergic), then call 911--go to hospital asap. If your symptoms are present for less than 3 hours, you may qualify for IV infusion of tpa (alteplase), (alteplase) a "clot buster". There is controversy over how long from the onset of symptoms to infusion of tpa (alteplase) is acceptable. It may be as long as 4.5 hours.
Clot busting. You are probably referring to clot busting medicines that can reverse the clotting process and open up the blood vessels. These can be used for patients whose stroke is identified rapidly, have a blockage (not a bleed), and have no reasoons the powerful medicines could cause a bleed such as recent surgery, .