By Lynne Adkins

PHILADELPHIA (CBS) — Millions of Americans know they have a common heart rhythm irregularity, but many more may be unaware, and that can be a huge problem.

Atrial Fibrillation is an irregular heart rhythm that puts a patient at higher risk for stroke.

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Dr. Peter Kowey, a cardiologist at Lankenau Heart Institute says millions take medication for the problem, but many others don’t know they have an issue.

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“We may be dealing with 2-3 times the number of patients in the population who have this arrhythmia who may be walking around with it and don’t know it,” Kowey said. “The catastrophe is that some of these patients the first manifestation of the arrhythmia is when they present in the emergency room with a stroke.”

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Older patients with kidney disease or sleep apnea, those with high cholesterol and high blood pressure should make sure their hearts are in normal rhythm.