Nav: Home

Imaging stroke risk in 4-D

October 07, 2016

Affecting 33.5 million patients worldwide, atrial fibrillation is the most common form of cardiac arrhythmia. As if having an irregular heart beat wasn't troubling enough, patients with atrial fibrillation are also much more likely to have a stroke.

"Atrial fibrillation is thought to be responsible for 20 to 30 percent of all strokes in the United States," said Northwestern University's Michael Markl, the Lester B. and Frances T. Knight Professor of Cardiac Imaging. "While atrial fibrillation is easy to detect and diagnose, it's not easy to predict who will suffer a stroke because of it."

Markl, who is a professor of biomedical engineering in Northwestern's McCormick School of Engineering and of radiology in the Feinberg School of Medicine, has developed a new imaging technique that can help predict who is most at risk for stroke. This breakthrough could lead to better treatment and outcomes for patients with atrial fibrillation.

Supported by the American Heart Association and the National Institutes of Health, the research was described online this month in the journal Circulation: Cardiovascular Imaging.

Atrial fibrillation is linked to stroke because it slows the patient's blood flow. The slow, sluggish blood flow can lead to blood clots, which can then travel to the brain and initiate stroke. Markl's cardiac magnetic resonance (CMR) imaging test can detect the blood's velocity through the heart and body. Called "atrial 4D flow CMR," the technique is non-invasive and does not require contrast agents. The imaging program, which images blood flow dynamically and in the three spatial dimensions, comes in the form of software that can also be integrated into current MRI equipment without the need of special hardware and scanners or equipment upgrades.

"We simply programmed the scanner to generate information differently -- in a way that wasn't previously available," Markl said. "It allows you to measure flow, diffusion of molecules, and tissue elasticity. You can interrogate the human body in a very detailed manner."

Historically, physicians have attempted to assess stroke risk in atrial fibrillation patients by using a risk scoring system, which takes risk factors, such as age, general health, and gender, into account. Higher risk patients are then given medicine to prevent blood clots that lead to stroke.

"It's very well accepted that these therapies significantly reduce the risk of stroke," Markl said. "But they also increase risk of bleeding complications. It's a dilemma that physicians face. They want to reduce one risk without introducing another risk. It's particularly difficult for younger patients who might be on these medications for a long period of time. Maybe the risk of bleeding is initially small. But after taking medication for 20 or 30 years, it's more and more likely that they'll experience complications."

Markl's 4D flow imaging technique can give a more precise assessment of who needs the medication, preventing physicians from over treating their patients. In a pilot study with 60 patients and a control group, Markl found that atrial fibrillation patients who would have been considered high risk for stroke by the traditional scoring system in fact had normal blood flow, while patients who were considered lower risk sometimes had the slow blood flow indicative of potential clotting.

"About 50 or 60 percent of patients who you would consider high risk actually had normal flows," Markl said. "You could then hypothesize that those 50 percent don't really need the treatment."

Markl plans to continue following atrial fibrillation patients as a part of a long-term study to better understand the predictive power and diagnostic value of his new imaging technique. His team is also developing algorithms and tools to make it easier to analyze the data.

"The challenge lies in the complexity of the technology," Markl said. "We want to integrate tools that help deliver test results within a matter of minutes."
-end-


Northwestern University

Related Stroke Articles:

Retraining the brain to see after stroke
A new study out today in Neurology, provides the first evidence that rigorous visual training restores rudimentary sight in patients who went partially blind after suffering a stroke, while patients who did not train continued to get progressively worse.
Catheter ablations reduce risks of stroke in heart patients with stroke history, study finds
Atrial fibrillation patients with a prior history of stroke who undergo catheter ablation to treat the abnormal heart rhythm lower their long-term risk of a recurrent stroke by 50 percent, according to new research from the Intermountain Medical Center Heart Institute.
Imaging stroke risk in 4-D
A new MRI technique developed at Northwestern University detects blood flow velocity to identify who is most at risk for stroke, so they can be treated accordingly.
Biomarkers may help better predict who will have a stroke
People with high levels of four biomarkers in the blood may be more likely to develop a stroke than people with low levels of the biomarkers, according to a study published in the Aug.
Pre-stroke risk factors influence long-term future stroke, dementia risk
If you had heart disease risk factors, such as high blood pressure, before your first stoke, your risk of suffering subsequent strokes and dementia long after your initial stroke may be higher.
Intervention methods of stroke need to focus on prevention for blacks to reduce stroke mortality
Blacks are four times more likely than their white counterparts to die from stroke at age 45.
Study shows area undamaged by stroke remains so, regardless of time stroke is left untreated
A study led by Achala Vagal, M.D., associate professor at the University of Cincinnati College of Medicine and a UC Health radiologist, looked at a group of untreated acute stroke patients and found that there was no evidence of time dependence on damage outcomes for the penumbra, or tissue that is at risk of progressing to dead tissue but is still salvageable if blood flow is returned in a stroke, but rather an association with collateral flow -- or rerouting of blood through clear vessels.
Immediate aspirin after mini-stroke substantially reduces risk of major stroke
Using aspirin urgently could substantially reduce the risk of major strokes in patients who have minor 'warning' events.
SAGE launches the European Stroke Journal with the European Stroke Organisation
SAGE, a world leading independent and academic publisher, is delighted to announce the launch of the European Stroke Journal, the flagship journal of the European Stroke Organisation.
The S-stroke or I-stroke?
The year 2016 is an Olympic year. Developments in high-performance swimwear for swimming continue to advance, along with other areas of scientific research.

Related Stroke Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Moving Forward
When the life you've built slips out of your grasp, you're often told it's best to move on. But is that true? Instead of forgetting the past, TED speakers describe how we can move forward with it. Guests include writers Nora McInerny and Suleika Jaouad, and human rights advocate Lindy Lou Isonhood.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...