Most pet owners find out their dog has a heart murmur during its yearly health checkup. A listen with a stethoscope should always be part of your pet's yearly examination. When a murmur is detected, the vet needs to make some other observations and, perhaps, run some tests even though your pet appears completely healthy. If your dog lives in a heartworm-prone area, they may want to run a heartworm antigen test. They will listen more thoroughly to...