Atlanta designed Heim for assignment Monday.
Heim served as Atlanta's No. 2 catcher behind Drake Baldwin after Sean Murphy (hip) opened the season on the 10-day injured list. With Murphy back from the IL, Heim's services are no longer needed on Atlanta's major-league roster, and it's unclear whether he will stay with the organization if he clears waivers. Heim is slashing .231/.311/.410 with one home run and eight RBI across 45 plate appearances this season.