New trial studies link between stroke and atrial fibrillation

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Cryptogenic stroke, or stroke of undetermined cause, accounts for 25% of all strokes. In many of these cases, physicians believe atrial fibrillation may occur without the patient’s knowledge, causing the stroke. To better understand the connection between atrial fibrillation and stroke, physician researchers from cardiology and neurology at Northwestern Medicine, Chicago, USA, have teamed up to monitor people diagnosed with a cryptogenic strokes for intermittent atrial fibrillation as part of a study called CRYSTAL AF (Study of continuous cardiac monitoring to assess atrial fibrillation after cryptogenic stroke).

“Patients with atrial fibrillation are at a greater risk for stroke than the general population,” said Rod Passman, medical director for the Center for Atrial Fibrillation at the Bluhm Cardiovascular Institute of Northwestern Memorial Hospital and associate professor of cardiology at Northwestern University’s Feinberg School of Medicine. “Fifteen per cent of all strokes are in patients with atrial fibrillation.”


The CRYSTAL AF trial will enrol approximately 450 people who have been diagnosed with a cryptogenic stroke across 55 centres. Approximately half will be continuously monitored by an FDA-approved implanted cardiac monitor. The device will monitor for the first documented event of atrial fibrillation following enrolment in the trial. Co-investigators Passman and Richard Bernstein, a neurologist at the Certified Primary Stroke Center at Northwestern Memorial and associate professor of neurology at Feinberg School of Medicine, are on the international steering committee for the CRYSTAL AF trial sponsored by Medtronic Cardiac Rhythm Disease Management.

“Screening for atrial fibrillation is routinely performed for a short period after a stroke as part of the evaluation for possible causes,” said Bernstein. “The participants who are enrolled in CRYSTAL AF and implanted with the device will essentially have an electrocardiogram (ECG) in their chest 24/7. This device has the ability to determine if and when atrial fibrillation occurs; allowing physicians like Dr Passman and me to better determine the optimal course of treatment and potentially prevent future strokes.”

To date, Northwestern Medicine researchers have enrolled 11 subjects in the trial, with four being implanted with the cardiac monitor. The continuous monitoring device captures and automatically stores any abnormal ECG activity. Passman and his team then review and analyse remotely-transmitted data. They can look at individually stored ECG episodes or longer-term trended diagnostic data, including atrial fibrillation burden, activity levels and average day/night heart rates. After the participants have been implanted, they are followed at one month and every six months thereafter for three years. The control group receives standard of care optimal medical treatment and follows up at the same intervals.

“The device is placed just under the skin in the chest area during a short outpatient procedure,” said Passman. “It is very small, about the size of a computer jump drive, and can provide up to three years of continuous heart rhythm monitoring and the device is compatible for use in an MRI environment.”