“What do you do if your dog's heart is racing?”

If you're dog's heart is racing due to anxiety, stress or exercise, you can calm them down by petting them with long gentle strokes down their back and use soothing (not high pitch) voices. However, if your dog's heart is racing while your dog is at rest (just sitting and doesn't seem stressed or anxious), then I would recommend taking your dog in to their primary care doctor or a cardiologist, as your dog may have an underlying heart condition.