Heart Disease in Dogs: What You Need to Know

When my husband and I adopted a senior Poodle named Peach, we knew she had a heart murmur. But when she began coughing almost to the point of retching, our veterinarian referred us to a veterinary cardiologist for more testing.

Sure enough, Peach has a leaky mitral valve. The resulting heart enlargement puts pressure on her trachea, causing her to cough. We managed her condition with fish oil supplements and regular exams for a year or so, but now her heart has enlarged to the point that she needs medication to help control her condition. Her cardiologist even gave us a special emergency dose of a drug to give Peach if she goes into heart failure.

Allison Heaney, DVM, MS, DACVIM (cardiology), veterinary cardiologist, and co-owner of Petcardia Veterinary Cardiology, which has four locations in Colorado including Fear Free certified Wheat Ridge Animal Hospital (where Peach is a patient), says many people don’t realize their dog or cat suffers from heart disease until their pet experiences congestive heart failure.

So what do we need to watch for?

In dogs, the most common form of heart disease is degenerative heart valve disease. It is seen primarily in small breeds but can happen to any size dog, Dr. Heaney says.

“We usually talk about the mitral valve as a one-way valve,” she explains. “It’s a valve in the heart that’s meant to keep blood flowing in one direction. When it degenerates, it becomes thicker and weaker and when it closes, it doesn’t seal off all the way and so there’s a leak back through that valve. That leak back to the valve is what we hear with our stethoscope, so that is what causes the heart murmur.”

A heart murmur is the most common sign that something is wrong with a pet’s heart, though an arrhythmia, or irregular heartbeat, can also signal dilated cardiomyopathy, a heart muscle disease that is more common in larger dogs such as Great Danes and Dobermans.

Since veterinarians typically detect clinical signs of heart disease before pet parents notice symptoms, it’s just one more reason why it’s so important to schedule regular checkups for our pets.

At home, we can watch for coughing (or a change in a cough), decreased energy levels, and changes in breathing patterns. The resting respiratory rate for a dog should be 25 to 30 breaths per minute.

Signs of congestive heart failure to watch for include an increase in the intensity of their cough or a change in the character of their cough. They might work harder to breathe, indicated by rapid respirations of 35 or more breaths per minute, or even faint.

Monitoring the respiratory rates of dogs while they’re sleeping is one of the best ways to detect progression of the disease. Count the number of breaths in a 15-second period and then multiply by four to get breaths per minute. In the meantime, maintaining a healthy weight and nutritious diet can help slow the disease.

Additionally, feeding fish oil supplements has been shown to help pets maintain heart muscle mass. A Tufts University study involving Boxers found fish oil decreased arrhythmia over a 6-week period.

Particularly when a dog’s heart shows signs of enlargement, a veterinarian will prescribe medication to delay onset of congestive heart failure, typically by about 15 months, Dr. Heaney says.

“There are definitely things we can do, even before they’re showing clinical signs, to try to delay the onset of congestive heart failure,” she says.

It’s important to note that heart failure is not an immediate death sentence. Medication can help maintain a dog’s quality of life for as long as possible. Median survival times for dogs after the first month of heart failure from degenerative heart disease are a year and half, and about a year for dilated cardiomyopathy, Dr. Heaney says.

She noted a study that found dogs with congestive heart failure live 75 percent longer when co-managed by a board-certified cardiologist and primary care veterinarian.

“So many of our clients come in thinking that heart failure is the end, and I think that for so many of our clients, the fact that they have this year and a half of good, quality time with their pet is often a bonus,” she says. “We’d like it to be much longer, obviously, but in the scope of a dog’s life, that’s a fair amount of time.”

This article was reviewed/edited by board-certified veterinary behaviorist Dr. Kenneth Martin and/or veterinary technician specialist in behavior Debbie Martin, LVT.

Award-winning journalist Jen Reeder is former president of the Dog Writers Association of America.
Photo: Jenna Dallaire