Ultrasound is a sound whose frequency is greater than upper limit of human hearing. The production of ultrasound is used in many different fields, and researchers are now tapping the potential of ultrasound technology in the field of stroke attacks. They have found that drugs combined with ultrasound fared better than taking medicines alone.
A study on the use of ultrasound technology or sonography (an ultrasound-based diagnostic imaging technique) was presented in the New England Journal of Medicine. It looks at using ultrasound in combination with the tPA drugs during an ischemic stroke attack.
The study involved 126 stroke victims. It showed that combining ultrasound technology with tPA showed an improvement in response to an ischemic stroke.
Traditionally, A TCD (Transcranial Doppler) device is used as an imaging device in the medical profession by emitting ultrasounds. It sends out high-frequency sound waves, which reflect off body structures, the computer receives these reflected waves and uses them to create a picture.
In this study, the TCD device was used as a mean of delivering ultrasounds on patients.
tPA (tissue Plasminogen Activator) is a thrombolytic agent or a clot-busting drug. It has been approved for use in certain patients having a heart attack or a stroke. tPA can dissolve blood clots, which cause most heart attacks and strokes. Ever since its discovery, tPA has been the drug of choice for ischemic strokes within a maximum of 4.5 hours after stroke onset. And from 1996 up to today, it is the only FDA approved therapy for an hyper acute ischemic stroke attack. Clinical studies have shown that it can greatly improve a patient’s chances for full recovery. However, it has been found ineffective and more harmful if used to treat the less common hemorrhagic stroke.
The research which is a first-of-its-kind human trial evaluated the safety and effectiveness of using ultrasound and tPA against the use of tPA alone. It focused on ischemic strokes and was funded in part by the National Institute of Neurological Disorders and Stroke (NINDS) of the US, America’s primary supporter of biomedical research on the brain and nervous system.
The study team wanted to determine the efficacy of using TCD combined with the drug tPA. Researchers also wanted to check that if this technology does or not cause bleeding into the brain and cause more harm than good to stroke victims. The study was named CLOTBUST (Combined Lysis of Thrombus in Brain ischemia Using transcranial ultrasound and Systemic tPA) by the research team, composed of scientists from all over the globe. They were led by Dr. Andrei Alexandrov, M.D., associate professor of neurology at the University of Texas-Houston School of Medicine. The study team examined a total of 126 stroke patients who had experienced an ischemic stroke. All of the stroke survivors had been given tPA within the three hours following the onset of their stroke. A total of 63 stroke patients received the drug tPA alone and these stroke survivors comprised the control group. The other half of the stroke subjects were given tPA in combination with TCD monitoring. These stroke victims underwent continuous TCD monitoring which started shortly before they received the drug. To deliver the ultrasound, a small device from TCD was attached to the heads of the 63 stroke victims.
Results of the study
Results of this groundbreaking study showed that 49% of the stroke patients who had tPA in combination with continuous ultrasound had shown dramatic clinical improvement. These stroke victims also showed little or no blockage within two hours after the therapy started compared to 30% of stroke survivors who received tPA alone. Notably, the study team found out that 38% of the stroke survivors who received the combination therapy showed no blockage within two hours compared to 13% who received only the drug tPA. In general, 73% of the stroke survivors who underwent continuous TCD with tPA showed complete or partial clearance of the clot. On the other hand, only 50% of the stroke victims who had tPA alone showed complete or partial clearance of the blockage. The study also showed that only 4.8% of patients in both stroke groups experienced bleeding into the brain.
The research team also noted that stroke patients who experienced complete clearance of the blood clot within 2 hours after their treatment had the greatest likelihood of recovering their body strength, speech and other functions which were affected by the stroke attack. Dr. Alexandrov was extremely enthusiastic: “In the past 30 years, scientists around the world have shown that ultrasound is fast, gentle, and effective in helping tPA to break up clots. For the first time, we have demonstrated this benefit in patients. This approach enhances flow to the brain and augments clinical recovery within minutes of treatment initiation.”
Stroke can be devastating for patients and their caregivers. These initial findings suggest that patients who receive the combined therapy are able to leave the hospital with a greater chance for recovery following an ischemic stroke.
The resulting vibrations caused by the ultrasound causes the molecules on and within the clot structures to shake. This action creates an increased number of binding sites for the drug tPA to interact with the clot and causes its breakdown. The study team assumes that this jiggling action greatly improves drug transport to and around the blockage. This helps in opening more blocked vessels faster than what can be expected if tPA therapy was used alone. The results of the study have caused elation among the scientific community more notably with the NINDS. Because of the study’s great impact in future stroke treatment the NINDS is funding additional research to standardize the combined therapeutic delivery system. They are also planning to make the study bigger by enlisting a larger group of stroke patients.