Doctors Administer Electrical Shock To Vice President's Heart To Restore Normal Rhythm

"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 went to the hospital around 5 p.m. --- About 2.8 million Americans have atrial fibrillation, the most common type of irregular heartbeat, and cases are increasing as the population ages.