Vice President Dick Cheney, who has a history of heart problems, experienced an irregular heartbeat Monday and will be evaluated at George Washington University Hospital.
The condition was detected when Cheney was seen by doctors for a lingering cough from a cold.
"During examination he was incidentally found to have an irregular heartbeat, which on further testing was determined to be atrial fibrillation, an abnormal rhythm involving the upper chambers of the heart," said spokeswoman Megan Mitchell.
She said Cheney would go to the hospital later Monday for further evaluation. She said that if necessary, he would be receive cardioversion, a procedure that involves the delivery of an electric impulse to the heart.
About 2.8 million Americans have atrial fibrillation, the most common type of irregular heartbeat, and cases are increasing the population ages.
The condition occurs when the heart's top chambers, called the atria, get out of sync with the bottom chambers' pumping action. It is not immediately life-threatening, and the heart sometimes gets back into rhythm on its own. Many times, patients aren't aware of an episode of atrial fibrillation.
But if the irregular heartbeat continues, it eventually can cause a life-threatening complication -- the formation of blood clots that can shoot to the brain and cause a stroke.
The main treatment is to try an electrical shock to restore normal heartbeat. If that doesn't work, patients may need to take the blood thinner warfarin to reduce stroke risk.
Other options include anti-arrhythmic drugs or, for severe a-fib, surgical procedures to interrupt the faulty heartbeat.