Bill Bradley left the presidential campaign trail in Northern California yesterday after suffering an irregular heartbeat, but his staff said he will return to a normal schedule on Sunday.

Bradley, 56, a former senator from New Jersey who is seeking the Democratic nomination, was taken to Sequoia Hospital near Palo Alto but did not need treatment, according to his campaign.

Anita Dunn, Bradley's communications director, said from the campaign's headquarters in West Orange, N.J., that the episode was "more of an inconvenience than a problem."

She said Bradley had called her from the hospital and said, "I'm fine. I got close to the hospital, and of course it went back into rhythm."

Bradley had undergone a checkup on Dec. 3, in preparation by the campaign to release a health report. Bradley had suffered three similar episodes of atrial fibrillation beginning in 1996, according to a letter from his doctor, which was dated Thursday and released by the campaign last night.

He was otherwise in good health, according to the doctor, Robert H. Heissenbuttel of Columbia Presbyterian Medical Center in New York.

"You have been evaluated and found to have no structural heart disease," the letter said. "When you have atrial fibrillation you note an irregular heart beat, but have no other symptoms. Thus, this rhythm does not, in any way, interfere with your ability to function. Other than the arrhythmia you have no other health issues."

The letter concluded, "Over the years you have enjoyed maintaining a high level of physical conditioning which I would encourage you to continue."

Heissenbuttel said Bradley had a small, benign polyp removed in April after a routine colonoscopy.

Cardiologists say atrial fibrillation is one of the more common abnormal heart rhythms and causes a fast, irregular heart rate. Although rarely life-threatening, it can cause feelings of breathlessness and lightheadedness if the rate is so fast that the heart doesn't have time to sufficiently fill with blood between beats. Atrial fibrillation that lasts more than a few days markedly increases a person's risk of stroke.

Bradley attended a fund-raising lunch in Berkeley yesterday, but then skipped a planned appearance at the Berkeley Marina, where he was to discuss coastal protection. He first had signs of the arrhythmia at a fund-raising reception in Los Angeles on Thursday, his campaign said. He was to stay in Northern California last night and then fly to Florida today for a speech on Sunday.

At a news conference yesterday morning in Sacramento, Bradley joked to reporters, "I'm freezing." They were wearing coats, and he had on a thin gray suit.

Staff writer David Brown in Baltimore and special correspondent Suzanne Marmion in Sacramento contributed to this report.