Patients with atrial fibrillation have a high risk of stroke — and while it’s easy to detect and diagnose, it’s difficult to predict risk. Researchers at Northwestern University developed a new 4-D MR imaging technique that can determine who is most at risk for stroke.

Between 2.7 and 6.1 million people in the U.S. have atrial fibrillation and the aging population is expected to make that worse, according to the Centers for Disease Control and Prevention. In addition, it's thought to be responsible for 20 to 30 percent of all strokes in the country.

Atrial fibrillation slows a patient’s blood flow and that can cause blood clots, which can travel to the brain and cause a stroke. The cardiac MR (CMR) imaging test called atrial 4D flow CMR can detect how fast the blood flows through the heart and body.
The technique doesn’t require the use of contrast agents and it's software that can be integrated into current MR equipment without requiring specific hardware, scanners, or equipment upgrades.

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

Physicians traditionally use a risk scoring system to predict stroke risk in atrial fibrillation patients. It assesses risk factors including age, general health, and gender, and the higher-risk patients are given medicine to prevent blood clots.

The medications do reduce the risk of stroke, but they also increase the risk of bleeding complications. Younger patients may be on them for a long period of time and their risk of bleeding may be small in the beginning. But after twenty to thirty years there’s more of a chance that they’ll have complications.

The scoring system also isn’t very accurate. In a pilot study that included sixty patients with atrial fibrillation and a control group, the Northwestern researchers found that those who would have been considered high risk by the scoring system had normal blood flow and those who were considered lower risk sometimes had slow blood flow.

Markl and his colleagues plan to continue to assess atrial fibrillation patients for a long-term study, to get a better understanding of the predictive power and diagnostic value of the new technique. They are also developing algorithms and tools to make it easier to analyze the data.

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