Ultrasound waves appear to dramatically boost the power of tissue plasminogen activator (t-PA) to dissolve cerebral blockages, a new study suggests. Researchers estimate that combining ultrasound with the fibrinolytic medication could help about 15% of the nation's stroke victims.
In a study of 126 patients with acute ischemic stroke from blockage of the middle cerebral artery, researchers gave half the patients t-PA alone and the other half both t-PA and continuous 2-MHz transcranial Doppler ultrasonography.
Within 2 hours of treatment, 49% of patients in the ultrasound group had blood flow restored in the artery or a dramatic recovery from symptoms, compared with 30% of patients who received t-PA alone. Three months after treatment, 42% of patients who'd received t-PA and ultrasound were free from symptoms or living independently, compared with 29% of those who'd received just t-PA.
Researchers suspect that sound waves may stir up blood near the clot, which may help mix in the drug or help the drug bind directly to the clot. Another theory is that the sound waves help break up the clot.
The ultrasound technique currently being tested is used only with t-PA, which is contraindicated if intracranial bleeding is present or suspected. Patients who are eligible to receive t-PA must receive it within 3 hours of stroke onset.
At present, too few skilled transcranial Doppler technicians are available to bring this technique into widespread use. While some researchers are working on creating a device that's easy to operate, others are investigating whether ultrasonography can be used to break up clots by itself.
Ultrasound-enhanced systemic thrombolysis for acute ischemic stroke, The New England Journal of Medicine. A Alexandrov, et al., November 18, 2004.