Silva returned to Chicago, and consulted with a Cubs physician about the abnormal heart rate that caused the pitcher to leave Sunday's game at Colorado in the first inning.
"It was a very scary moment," Silva said. "I was feeling bad, but when they put me inside the ambulance, I think that was the first time I put my family before baseball. The only thing I could think of was my kids and my family. It was very tough to be in that situation."
Silva will continue his evaluations under the care of a cardiologist at Northwestern Hospital. There is no timetable for his return as he undergoes tests.
"Right now, I'm doing whatever they tell me to do, because I know they're going to do what's best for me," Silva said before the Cubs played the Milwaukee Brewers. "I feel better. I was throwing my bullpen and felt like my heart was beating very fast."
To fill Silva's spot on the roster, the Cubs recalled pitcher Thomas Diamond, who will start against the Brewers on Tuesday.
A Cubs trainer went to the mound Sunday after Silva walked the second batter he faced, Jonathan Herrera. Silva stayed in and allowed asingle to Carlos Gonzalez and a ground-rule RBI double to Troy Tulowitzki.
Acting manager Alan Trammell and the trainer went back to the mound, and Silva wasreplaced by left-hander James Russell.
Chicago Cubs RHP Carlos Silva leaves in bottom of the firstSilva concentrating on World Cup
