Can someone help me? My beautiful, black lab, Shelby, was diagnosed with heartworms. The vet told me that her bloodwork showed a lot of baby heartworms

So, I scheduled for her first treatment. The first treatment was to attack the baby heartworms. Since that treatment, she's had very shallow, rapid breathing....almost what it would be like if I brought her in from a walk on a hot day...and she's doing this ALL the time. I took her back to the vet and now she's been given steroids to help. I've been told that she should return to normal soon. Has anyone ever seen or heard of this happening to a dog after microfilaria treatment? Please help!