Washington, D.C. ? Doctors examining Vice President Dick Cheney Monday discovered an irregular heartbeat and applied an electrical shock to restore a normal rhythm, the White House said, the latest in a long string of episodes that have raised concern about the health of the man next in line for the presidency.

Cheney went to his doctors complaining of a lingering cough, but during the checkup they determined that he was experiencing atrial fibrillation, an abnormal rhythm involving the upper chambers of the heart. His medical team sent the vice president to George Washington University Hospital for further tests, where it was decided that the electrical impulse was needed to restore a regular heartbeat.

“The procedure went smoothly and without complication,” the vice president’s office said in a statement issued by the White House Monday night. “The Vice President has returned home and will resume his normal schedule (today) at the White House.”

Cheney, 66, has a long history of heart trouble, including four heart attacks, most recently after the 2000 presidential election. He had a defibrillator implanted in 2001 to regulate his heartbeat.