The facts are grim. Stroke is responsible for more disabilities among American adults than any other disease. Every 3 minutes, an American dies from stroke. About 700,000 Americans suffer a new or repeat stroke every year, statistics show. More men than women suffer a stroke, yet women are more likely to die from a stroke than men. The risk of stroke among African Americans in the United States is about four times higher than that of non-Hispanic whites.
The Stroke Belt
First identified more than a half-century ago, the Stroke Belt, which stretches across 11 Middle Atlantic and Old South states, is where residents face a risk of stroke that is 50% greater than the national average.
Awareness challenges linger. On its Web site, the National Institute of Neurological Disorders and Stroke (NINDS) points out that those 75 and older—many at the highest risk—are the least likely to know the warning signs of stroke or how to evaluate their own risk factors.
In the NINDS study, investigators found that only 57% of those participating could correctly list at least one of the five common symptoms or warning signs; 28% correctly listed two or more, and 8% correctly listed three symptoms.
Results of the study, according to NINDS officials, point to the need for greater public education about stroke. The most frequent symptom survey respondents mentioned was dizziness, followed by numbness, headache, and weakness.
Recent research revealed that high doses of cholesterol-lowering statins not only reduced the risk of stroke, but also helped patients avoid second strokes and potential problems from heart disease. Stroke risk factors include high blood pressure, high cholesterol levels, diabetes and obesity, smoking, illegal drug use, and physical inactivity.
Research at Morehouse School of Medicine
Examining and remedying the racial and geographic disparities related to stroke and cerebrovascular disease in the United States is the mission of the Stroke Prevention/Intervention Research Program (SPIRP) at Morehouse School of Medicine in Atlanta. Edgar J. Kenton III, MD, serves as director of SPIRP, and is a frequent spokesman for the American Stroke Association.
Part of reducing the burden of stroke in populations most at risk is knowing its impact on the poor and underserved within urban and rural African American communities.
Kenton says that African Americans between ages 35 and 55—in their peak earning years—are among those most at risk of stroke. Stroke association numbers indicate that African Americans as a group are four times more likely to become stroke victims than are non-Hispanic whites.
While lifestyle issues such as diet and exercise count as modifiable factors in stroke risk, an aging population – the graying of America, as Kenton describes it—ranks as an unmodifiable factor. “Aging really presents its own stroke risks,” he says. “Among people above the age of 55 years, the incidence of stroke doubles every decade.”
Although as a group men experience many more strokes than women, they also are much more likely to survive a stroke. “Women over 65 are twice as likely to die as men,” Kenton says. “One explanation is that older women tend to present later than men; they’re busy with families and households, and they often ignore symptoms.”
Imaging Is Key
Kenton says imaging tools play a pivotal role in diagnosing stroke and deciding appropriate treatments. He estimates that about 15% of strokes are hemorrhagic, involving bleeding into the brain. Most strokes are ischemic, involving clots. Imaging technology is the best way to determine stroke type, according to Kenton.
“We get a CAT scan first since we have a 3-hour window for the t-PA,” Kenton says. Tissue plasminogen activator (t-PA) is a clot-busting drug approved 10 years ago by the US Food and Drug Administration for treating ischemic stroke in the first 3 hours after symptoms appear. Given immediately, t-PA has been shown to reduce stroke effects and the risk of permanent disability. The drug is administered intravenously by trained staff.
A frequent first response when the patient gets to the hospital is scheduling of a computed tomography (CT) scan. CT, used with other imaging, signals the type of stroke and the extent of bleeding and tissue damage. The results frequently dictate which treatment options and rehabilitation regimen the physician chooses to use.
Another imaging option is magnetic resonance imaging (MRI). Kenton says the MRI’s higher degree of resolution can show brain-stem lesions that a conventional computed axial tomography scan may not pick up. “MRI also has the ability to help detect a smaller stroke earlier,” he says. A less invasive tool is magnetic resonance with an angiogram (MRA). The MRA is available in two methods: time of flight and phase contrast. Both approaches use pulse sequences and 2D or 3D volume acquisitions. These approaches generate an MR angiogram that maps images of affected neck vessels from different angles. CT angiography using x-rays is yet another option.
New diffusion MRI offers the promise of identifying a stroke much earlier than conventional MRI, so physicians don’t lose valuable time initiating treatment. Also, researchers are finding that diffusion MRI helps them find new neuroprotective agents—drugs that save brain cells near the stroke area within the brain.
Though he hasn’t used the MERCI® Retriever, Kenton says he has been impressed with the results of the corkscrew-like tool, introduced 2 years ago, that uses standard catheterization techniques to remove blood clots and restore blood flow. It is used only for ischemic strokes as an option to clot-busting drugs or when a patient shows up after t-PA’s 3-hour window closes.
The use of cholesterol-lowering statins is among the most common regimens for stroke victims, Kenton says. Also on the horizon are new neuroprotective agents. “However, bigger trials are definitely needed, because the results so far have been small,” he says.
Public awareness of stroke and greater education are a continuing challenge, according to Kenton. Only 3% to 5% of patients who have suffered a stroke are getting t-PA, he says. Most patients with stroke symptoms don’t get to the hospital until 22 hours have elapsed; often, they arrive in a car or other vehicle driven from home or work by friends or family.
“Those with stroke symptoms should call 911 and get in an ambulance as soon as possible,” Kenton says. “That way, medical treatment can begin immediately; medical personnel are in contact with the hospital.”
Increasing Education and Awareness
The American Stroke Association (ASA)’s current “Power to End Stroke” campaign aims to make persons responsible for learning stroke’s warning signs and the appropriate way to react to them, according to Kenton. The association’s strategy is to identify stroke champions that help spread stroke information through the print media, television, social settings such as barbershops and beauty salons, and churches in the community.
Asked about the use of hyperbaric oxygen therapy for treating ischemic strokes, Kenton says an ASA committee he chaired looked at that and other possible treatments. “We could never find any medical evidence to suggest or support the efficacy of hyperbaric oxygen as a therapy,” Kenton says.
Strategies In the Stroke Belt
David Y. Huang, MD, PhD, is assistant professor, Department of Neurology, at the University of North Carolina (UNC) School of Medicine. He also serves as associate director and director of inpatient and emergency neurology at the UNC Stroke Center.
Among Stroke Belt states, Huang says, North Carolina has taken significant action to promote stroke awareness, treatment, and prevention initiatives. The state currently boasts eight Joint Commission on Accreditation of Healthcare Organizations (JCAHO) primary stroke centers and will see two more facilities soon apply for JCAHO certification.
“If I could get one thing accomplished, it would be to improve the education of the public in regard to strokes,” Huang says. “The majority of people get to the hospital too late; they think they can sleep it off. Only 15% to 25% of patients show up within 3 hours. For the rest, we are limited to working on preventing another stroke and providing intensive rehabilitation.”
Although the Chapel Hill hospital facility served as a trial site for the MERCI Retriever, the device is used, on average, only once every 2 months or so, Huang says. The MERCI catheterized device can only be used during the first 8 hours after a stroke occurs.
“Besides the 8-hour window, the MERCI only works on large and medium-sized clots,” Huang says. “Actually, when clots are in vessels smaller than 2 millimeters, they can’t be pulled out.”
Huang is optimistic about the promise of newly developing neuroprotective drugs such as AstraZeneca’s NXY-059. Tested for the ability to reduce disability in humans who suffer ischemic strokes, NXY-059 is a free-radical trapping agent that has been applied to animal models with stroke. “Data I have seen suggest that the NXY-059 could make you better and the side effects are pretty benign,” Huang says. “But a lot more study is necessary.” After an initial study focused on patients chosen from around the world, a second study on how the drugs affect Americans and Canadians is scheduled for release next spring.
As for the application of hyperbaric oxygen therapy, Huang says driving more oxygen into the brain could prove to be beneficial at preventing stroke, but he has seen little clinical evidence that it offers any after-stroke treatment potential.
Making A Difference
In the 1990s, the director of the University of California at San Diego (UCSD) and VA Stroke Centers in San Diego, Patrick Lyden, MD, helped lead clinical trials sponsored by the National Institutes of Health for t-PA, the enzyme for dissolving arterial blood clots. Lyden’s research has also focused on the effectiveness of new blood thinners, compared to aspirin and coumadin, in preventing recurring strokes.
“Our stroke center has enormous impact in San Diego, in terms of delivering medical care,” Lyden says. “We treat about 15% of the stroke patients we are called to see—well above the national average of 2%.”
At the national and international level, the UCSD Stroke Center provides research leadership in the area of stroke scales and organizing stroke care. “Through the UCSD Clinical Trials Coordinating Center, we also help manage large, multi-center, multi-national trials,” Lyden says.
His center is halfway through a 5-year, $5 million NINDS grant that seeks new techniques for extending brain-saving stroke treatments to more patients. Ultrasound screening and remote consultations via wireless technology are being used to offer more timely treatment to a larger base of stroke patients.
“I think the future of neuroprotection is very promising, but the last 10 years show a track record of failures. My guess is that within 5 years, maybe a lot sooner, we will have an effective neuroprotectant available for human use,” he says.
Nicholas Borgert is a contributing writer for Clinical Lab Products.