Outcomes of Patients with Lone Atrial Flutter

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The summary below is from the full report titled "The Natural History of Lone Atrial Flutter." It is in the 17 February 2004 issue of Annals of Internal Medicine (volume 140, pages 265-268). The authors are S.C. Halligan, B.J. Gersh, R.D. Brown Jr., A.G. Rosales, T.M. Munger, W.-K. Shen, S.C. Hammill, and P.A. Friedman.

What is the problem and what is known about it so far?

The atria are the upper chambers of the heart. Atrial fibrillation and atrial flutter are abnormal heart rhythms that occur when the atria do not beat normally. Atrial fibrillation is the most common abnormal heart rhythm. It involves a rapid, irregular heartbeat that can cause symptoms such as pounding in the chest or lightheadedness. Atrial flutter is less common and involves a very rapid but regular heartbeat, a "short circuit" in the atria. Heart, lung, and thyroid disease increase the risk for atrial fibrillation and atrial flutter, but both can occur in healthy people. When they occur in people without underlying disease, these heart rhythms are called "lone atrial fibrillation" or "lone atrial flutter." The most serious complication of these conditions is the formation of blood clots in the atria that travel to the brain, causing strokes or transient ischemic attacks. In transient ischemic attack, blockage of blood flow to the brain is temporary and no permanent damage occurs. In stroke, blockage of the blood flow lasts long enough that a section of brain tissue dies. Stroke occurs in about 10 of every 100 patients with atrial fibrillation each year. Treatment with blood thinners can reduce the risk for this complication and is standard treatment for most patients with atrial fibrillation. Because lone atrial flutter is uncommon, we know little about what happens to patients with this condition.

Why did the researchers do this particular study?

To describe what happened to patients with lone atrial flutter over time.

Who was studied?

59 patients with lone atrial flutter that was diagnosed at the Mayo Clinic from 1965 to 1995. Comparison groups included a group of healthy residents of Rochester, Minnesota, who were participating in a study of stroke rates and patients at the Mayo Clinic who received a diagnosis of lone atrial fibrillation from 1950 to 1998.

How was the study done?

The researchers reviewed the Mayo Clinic medical records to determine what happened to the patients with lone atrial flutter and the comparison group from the time of diagnosis or study entry through January 2001.

What did the researchers find?

More than half of the patients with lone atrial flutter developed atrial fibrillation. Patients with lone atrial flutter developed stroke or transient ischemic attack more often than did patients in either comparison group. After 10 years, 35% of the patients with lone atrial flutter had experienced a stroke or transient ischemic attack.

What were the limitations of the study?

This study relied on medical records of one medical center and may have missed events if patients got care somewhere other than Mayo Clinic. In addition, the researchers did not specifically evaluate all patients for underlying disease but just assumed that patients had none if the medical record did not mention it.

What are the implications of the study?

Patients with lone atrial flutter seem to have a risk for stroke or transient ischemic attack that is at least as high as that in patients with lone atrial fibrillation. Doctors should consider blood thinners for patients with atrial flutter, especially in patients older than 65 years of age.