Timing can be everything for the unfortunate victims of a stroke. To that end, approximately 800,000 strokes occur in the United States each year, of which 600,000 are ischemic strokes.
There are two major types of stroke: ischemic stroke and hemorrhagic stroke.
Ischemic stroke occurs when a blood vessel that supplies blood to the brain is blocked by a blood clot. This may happen in two ways:
A clot may form in an artery that is already very narrow. This is called a thrombotic stroke.
A clot may break off from another place in the blood vessels of the brain, or from some other part of the body, and travel up to the brain. This is called cerebral embolism, or an embolic stroke.
Ischemic strokes may be caused by clogged arteries. Fat, cholesterol, and other substances collect on the artery walls, forming a sticky substance called plaque.
A drug called tissue plasminogen activator -- tPA -- dissolves clots and restores blood flow.
However, the drug must be given timely, or the effectiveness may not outweigh the risk of hemorrhage.
As a stroke malpractice lawyer, I have represented numerous individuals who had unfortunate outcomes, because the doctors did not timely recognize that their patient was having a stroke, or did not recognize that their patient was suffering from a transient ischemic attack(TIA), and would later go on to have a stroke.
The guidelines for administration of tPA required administration within 3 hours from onset of symptoms. However, a 2009 study published by the American Stroke Association found that certain patients may still receive a benefit up to 4.5 hours after the onset of symptoms.
Patients who cannot receive tPA more than three hours after a stroke:
Patients over age 80
Patients taking blood thinning drugs (anticoagulants)
Patients with a history of stroke and diabetes
Thus, a majority of the population may still benefit from the administration of tPA up to 4.5 hours from the onset of stroke symptoms. While it is still not a lot of time for treatment, the window has increased by 50%.