Marcus Welby meets Joe Gannon. Guest star Richard Bradford originated the role of Dr. Joe Gannon in the 1969 television movie pilot "Operation Heartbeat" aka Operation Heartbeat (1969). When Medical Center (1969) went into production as a series, Bradford was replaced by Chad Everett. "Marcus Welby, M.D". and "Medical Center" were rival shows, each enjoying seven-season runs spanning 1969 through 1976.