Atrial fibrillation—the rapid and ineffectual quivering of the heart’s upper chambers—dramatically increases a person’s risk of having a stroke. In fact, doctors estimate that about 15% of all strokes arise from atrial fibrillation. But a even greater proportion of strokes—25%—have no known cause. A new study suggests that hidden atrial fibrillation could account for many of these strokes as well.
Doctors use the term “subclinical” to describe a disease that’s hidden. People don’t feel any symptoms of it, and nothing abnormal shows up in routine medical tests. But it’s there.
Researchers looked at more than 2,500 people ages 65 and older who had recently received an implanted pacemaker or defibrillator. These people had no prior history of atrial fibrillation, having received the implant to treat another heart problem.
Looking for hidden signs of atrial fibrillation, researchers scoured data taken over a three-month period from the implanted devices. They found evidence of silent atrial fibrillation in more than 10% of the people. What’s more, those with it were more than twice as likely to have a stroke during the subsequent two and a half years as those who didn’t have hidden atrial fibrillation (New England Journal of Medicine, Jan. 12, 2012).
These findings don’t mean that everyone should run out and get an implanted pacemaker or defibrillator. Continuous Holter monitoring of the heart for a couple of days or using an event recorder—which captures electrocardiographic information only when symptoms arise—are more sensible early steps in detecting atrial fibrillation.
But if you already have an implanted pacemaker or defibrillator, ask your doctor to periodically “interrogate” the device in search of otherwise hidden atrial fibrillation. If it’s there, several approaches to treatment are available, and taking a blood thinner can substantially reduce the accompanying stroke risk.