Stroke is the fourth leading cause of death and the leading cause of disability in the U.S. The drug tPA has been pretty effective at dissolving blood clots that can lead to stroke. But that's only if given within three hours and if the clot isn’t large. The Food and Drug Administration this year approved two mechanical devices doctors can use beyond the three hour window to remove large clots from the brain. In a KERA Health Checkup, Dr.