Silva was hospitalized with an abnormally high heart rate during a game with the Colorado Rockies Sunday and was taken to Denver's St. Joseph Hospital. The problem was corrected en route to the hospital but Silva was kept overnight for observation, before being discharged Monday morning, the Chicago Tribune reported.
The team later placed Silva on the 15-day disabled list as a precaution.
"It was a very scary moment because I was feeling bad, but when they put me in the ambulance I think it was the first time I put my family before baseball," Silva told the newspaper. "The only thing I was thinking about was my kids and family."
He said it wasn't the first time he had felt his heart race, but it had always gone away before.
Denver's high altitude may have affected Silva. He told trainers he was having trouble breathing and his heart was racing. A check of his heart rate showed it to be abnormally high.
Silva was set to be seen by the team cardiologist upon returning to Chicago, the Tribune reported.
To take Silva's spot on the roster, the club recalled right-handers Casey Coleman and Thomas Diamond from Class AAA Iowa.