The professional football team announced Richardson has been receiving medical care at the Carolinas Medical Center in Charlotte since last week, when the 72-year-old fell ill, The Charlotte (N.C.) Observer said Thursday.
The franchise said a pacemaker that Richardson received in June was still operating well and the team owner has undergone several tests to determine the cause of his sudden illness.
CMC spokesman Scott White said the median waiting time at the medical site for a possible heart transplant patient is nearly two months.
White added that the center has completed a total of 428 heart transplants since 1986 and its success rate is commensurate with national averages.
Meanwhile, NFL spokesman Greg Aiello offered the league's support to Richardson and his family.
"The entire NFL team is thinking of Jerry and his family," Aiello said.
The Panthers are currently 10-3 on the season and in first place in the National Football Conference's South division.