DeRosa, who turns 33 on Tuesday, was kept overnight at Banner Desert Medical Center in Mesa after experiencing a rapid heartbeat during fielding drills on Saturday. He was released from the hospital around 5 p.m. MT on Sunday.
"He's doing fine," Cubs manager Lou Piniella said Sunday. "They kept him overnight for caution. He's here by himself, his family wasn't with him. They were going to do one more test today, and they thought that by noon time he would be going home. We're going to have to be precautious the next few days but there's really nothing to concern ourselves about."
One of the tests DeRosa underwent on Saturday took longer than expected, so he was kept overnight for observation. Cubs team physicial Dr. Stephen Adams spoke on DeRosa's behalf Sunday.
"He had an episode yesterday of an atrial dysrhythmia that he's had in the past, and that he's had in the past lasted briefly," Adams said. "This one had a bit of an extended period of time, for which he contacted our head athletic trainer, Mark O'Neal, who appropriately saw him and was with him. When it didn't break with his usual manuevers that it breaks with, we decided to take him to the hospital to have him monitored and he went into a normal sinus rhythm yesterday from the atrial rhythmia."
DeRosa's heart condition is not expected to keep him from playing this year. He cannot resume baseball activities until the Cubs medical staff sees the test results. Adams said he expected to know more Monday.
"I don't anticipate it'll be an extended period at all," Adams said of the time off.
DeRosa has had atrial arrhythmia (also known as atrial dysrhythmia) for a few years.
"It doesn't occur very often," Adams said. "This one just extended longer than usual."
Asked if DeRosa ever faced a life-threatening situation Saturday, Adams said, "No."
On Saturday, Piniella kept in touch with O'Neal, who was with DeRosa at the hospital.
"I said, 'Tell [DeRosa] I was thinking about him and I was happy he was going home,'" Piniella said.
Some of his teammates stopped by to check up on the second baseman.
"Jason [Marquis] and I went right after practice, and hung out for a couple hours," Cubs shortstop Ryan Theriot said Sunday. "Everything was back to normal and he seemed fine. He was cracking jokes in there. Obviously, it's a scary thing but he seemed fine. I offered for him to come and hang out at the house and play guitar with the kids."
"The doctor was like, 'You guys do whatever you like,'" Theriot said.
However, the incident was a little scary.
"He seemed more shaken up and a little scared about it," Theriot said. "When I read the reports [streaming] on ESPN, it scared me and I was there the whole time."
Matt Murton sent DeRosa a text message, and got a quick response.
"He said, 'I'm sorry I scared everybody. It's something that's been happening since I was a little kid,'" Murton said.
DeRosa felt faint but never lost consciousness.
"He's had a history of this," Piniella said. "Usually he's been able to correct it himself. This time here, he wasn't. Because of it, I think he got a little nervous. When he saw the paramedics walk in [on Saturday], I think it made him a little more nervous."
Carrie Muskat is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.