The Angels made the move Wednesday, one day after Heaney made his first start of the season.
Heaney yielded seven hits and four runs over six innings in the Angels' 6-1 loss to the Chicago Cubs on Tuesday. He complained of tightness in his left forearm afterward, and an MRI exam revealed the strain.
Heaney has been shut down from throwing to rest the muscle. The team does not know how long he'll be shut down.
Heaney was the Angels' No. 2 starter entering his first opening day on a big league roster. He went 6-4 in 18 starts last season.
Nick Tropeano is likely to replace Heaney in the Angels' rotation.