Unsteady heart rhythm sometimes normal in dogs

Q:I am in high school and want to become a veterinarian, so I’ve been listening to my pets’ hearts with a stethoscope. My dog’s heart rate varies considerably, going from fast to slow to fast again, but my cat’s heart beats steadily – as does mine, even though I am worried about my dog. Does he have heart disease?

A:What you likely hear is called sinus arrhythmia, and it’s normal in dogs, but not in cats.

In relaxed dogs, the heart rate quickens during inhalation and slows when the dog exhales and pauses between breaths. By comparison, a cat’s heartbeat remains steady.

To convince yourself that your dog’s changes in heart rhythm constitute normal sinus arrhythmia, take him for a run and, while his heart rate is still elevated from the exertion, listen again. You should hear steady, evenly spaced heart beats.

If you are in doubt about his heart, ask your veterinarian to listen and be prepared with dog insurance.

Lee Pickett, V.M.D. practices companion animal medicine in Pennsylvania. Contact her at askdrlee@insurefigo.com.