Duration of Atrial Fibrillation Linked to Short-Term Increase in Stroke Risk

Analysis of continuous heart rhythm and outcome data indicates that temporary cases of atrial fibrillation (AF) do raise stroke risk — but the worst danger lasts only a few days after the heart returns to normal rhythm.

Previous studies had reached varied conclusions about whether short bursts of AF were associated with a greater risk of stroke, and there is little agreement about whether they require treatment and, if so, what sort of treatment is appropriate.

Researchers from Stanford University worked with Medtronic and Massachusetts General Hospital to identify 9,850 patients who had received cardiac implantable electronic devices (CIEDs) through the Veterans Administration Health Care System (VA) between 2002 and 2012. They then analyzed all the CIED data that was transmitted to VA hospitals and compared that data with patient outcomes.

This strategy uncovered full and continuous heart rhythm data for the 120 days preceding ischemic stroke in 187 patients (average age 69±8.4 years). The researchers then compared each patient’s daily AF burden in the 30 days before each stroke with their average AF burden 91 to 120 days before each stroke.

Overall, 156 patients (83%) did not exhibit positive AF burden (which was defined as more than 5.5 hours of AF on any given day) in either period. Another 15 patients (8%) has positive AF burden in both periods. Another 13 patients exhibited AF burden in the 30 days before their strokes but not in the period 91 to 120 days before their strokes, while the final 3 patients exhibited AF burden 91 to 120 days before their strokes but not in the month immediately before the strokes took place.

Using these figures to calculate the danger of temporary AF, the researchers found that stroke risk increased to 17.4 times its normal level (95% confidence interval, 5.39-73.1) during the five days after a qualifying AF event and decreases toward its normal level by the time patients have gone 30 days without any additional AF.

The study team, which published its findings in Circulation: Arrhythmia and Electrophysiology, warned that a potential weakness in the study was the relatively small number of patients who had short-lived bouts of AF in only 1 of the 2 periods before their strokes. They were the only patients who provided information about the stroke risk associated with temporary AF and the small number of them led to the wide rage of stroke risk ratios within the confidence interval. Still, the research team concluded, the data provide the best information yet on the risks associated with sudden, temporary AF and the underlying technique has the potential to make far more useful findings.

“This is truly a big data approach, where we took raw data from implanted pacemakers and implanted defibrillators and linked it to clinical data. The medical device data comes from home remote monitoring systems that patients have and goes to the cloud. We pulled the raw data off the cloud and linked it to VA electronic health records, VA claims, Medicare claims, and death records,” wrote Stanford cardiac electrophysicist Mintu Turakhia, MD, in an e-mail that explained the study. “This is truly a novel approach where we are assembling highly disparate data sources and linking them to gain insight into disease.”