It was one of those findings that would change medicine, Dr. Christopher Lewandowski thought.

For years, doctors had tried — and failed — to find a treatment that would preserve the brains of stroke patients. The task was beginning to seem hopeless: Once a clot blocked a blood vessel supplying the brain, its cells quickly began to die. Patients and their families could only pray that the damage would not be too extensive.

But then a large federal clinical trial proved that a so-called clot-buster drug, tissue plasminogen activator (T.P.A.), could prevent brain injury after a stroke by opening up the blocked vessel. Dr. Lewandowski, an emergency medicine physician at Henry Ford Health System in Detroit and the trial’s principal investigator, was ecstatic.

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