An irregular heartbeat, medically known as atrial fibrillation (AF) or cardiac arrhythmia, may double a person’s stroke risk, even if it is not felt, this according to a new study in the Jan. 12 issue of the New England Journal of Medicine.

The study followed 2,580 patients with pacemakers, a device placed in the chest to control abnormal heart rhythms. More than one-third of participants experienced pacemaker-documented episodes that lasted more than six minutes, according to researchers. Of the participants who experienced episodes, 85 percent didn’t even realize it because they were unable to feel any symptoms.

“In patients with pacemakers, we do see a very high prevalence of silent AF that is not recognized by the patient,” study author Dr. Jeff Healey, said. “Even though they are silent, these episodes are clearly associated with risk of stroke.”

Participants who experienced at least one undetected atrial fibrillation episode within the first three months of the study were twice as likely to eventually have a stroke compared to those who did not experience an episode.

All study participants were at least 65 years of age and had a history of high blood pressure.

Although the research is thought-provoking, according to experts, common sense should still prevail.

“We should not check everyone for silent AF,” Dr. Marc Gillinov, a Cleveland Clinic heart surgeon said. “If you feel palpitations or your heart racing, let your doctor know, but otherwise I would not rush to the doctor. The cause of the stroke is unknown in about 25 percent of people, and a lot of us think maybe subclinical AF plays a role. This study helps answer that piece of the puzzle.”

Stroke is the third leading cause of death in the United States, with more than 140,000 people dying each year.