Boone became aware of the problem at practice Friday. He missed the Nets' game at Boston on Sunday and had tests Monday, which were inconclusive. He is scheduled for further testing Wednesday.
Boone said he had a little cold last week but wasn't sure if that had anything to do with the heartbeat issue. He said he has been told there was no reason for long-term concern, and hopes he can return Wednesday night against Philadelphia if he is cleared that afternoon.
"The doctor said today just really limit what you do. You don't want to risk anything just in case," Boone said. "It's probably not going to be -- he used the words 99 to 100 percent not life-threatening -- or not really a big issue, but it's just more of a precautionary measure."
Boone averaged career highs of 8.2 points and 7.3 rebounds in 70 games last season, including 53 starts.