A Look at Canine Heart Disease


We all know it’s important to eat right and exercise in order to stay healthy, and we try our best to do it for ourselves and our pets. Unfortunately, diet and exercise are not always able to stave off medical problems.

The term “heart disease” encompasses many medical conditions and can have many underlying causes. Canine heart problems include diseases of the heart muscle itself, valvular malfunctions, and electrical disturbances that affect heart rate and rhythm. And they are seen in dogs of all sizes.

In dogs, as in humans, the heart is basically a pump; it is mostly muscle tissue and contains four chambers and four valves. The beating heart pumps blood that delivers nutrients and oxygen to cells while removing waste products for elimination. Each heartbeat is a coordinated muscle contraction.


Cardiomyopathy in Large Breeds

When the heart muscle itself becomes abnormal, the condition is referred to as cardiomyopathy. The most common type in dogs is dilated cardiomyopathy (DCM). DCM hearts become enlarged because the muscle stretches and becomes thinner. The result is a heart that pumps inefficiently. AS DCM progresses, dogs become less active, they may cough or wheeze, and they sometimes appear bloated as fluid accumulates.

DCM is largely genetic and more commonly seen in larger breeds, such as Dobermans and Boxers. Treatment involves medications that help the heart muscle contract more efficiently and decrease heart size by reducing the amount of blood in the heart at any given time.


The Smaller Dog’s Disease

Valves prevent the backflow of blood as it exits the heart. Each one-way valve is a delicate membrane held in place by tiny strands of tissue. Considering the countless number of heartbeats in an average lifetime, the durability of these paper-thin valves is remarkable. Sometimes, however, the valve tissue can thicken, changing shape and losing flexibility. This condition is referred to as endocardiosis.

Endocardiosis is often first detected by the presence of a murmur. Heart murmurs are caused by abnormal blood flow through the heart. If a valve is abnormal, blood cannot exit the heart efficiently. Increased volume of blood in the heart stresses the heart muscle over time and exacerbates the problem.

Smaller dogs, such as Poodles, King Charles Spaniels, and Chihuahuas, are most commonly affected by this disease. Endocardiosis may have no symptoms, but it can progress to the same symptoms as DCM. Most dogs with endocardiosis are treated with medications that decrease the heart’s workload.


Bacterial Infection

Occasionally, heart valves can develop a bacterial infection known as endocarditis. This infection can be very sudden and is a serious life-threatening disease that must be treated with high doses of antibiotics. 

While the cause of endocarditis is not always know, chronic bacterial infections elsewhere in the body are often implicated. Periodontitis (infection of the gums and deeper tissues) is by far the most common type of chronic infection in dogs.


From Mosquitoes to Dogs

The disease processes mentioned above have similar counterparts in humans, but heartworm disease is largely restricted to dogs. Heartworms are parasites transmitted by mosquitoes. After going through several life stages in a dog’s tissues and bloodstream, adult heartworms reside within the heart. This obstructs blood flow and leads to excessive stress on a dog’s heart and lungs. 

Heartworm disease is easily prevented, but it can be deadly to animals already infected. Your veterinarian can discuss with you the various products that are effective at preventing heartworm disease.

In general, canine heart disease is difficult to prevent because it is often genetic in nature. Your best option is routine physical examinations by your veterinarian in order to detect and treat any problems as early as possible. The goal of treating heart disease is maintaining the best possible quality of life for the patient.

Long before scientists learned how the body works, they understood that when the heart stops, everything stops. With this in mind, it behooves us all to be proactive when it comes to the prevention, diagnosis, and treatment of canine heart disease.

Dr. Gary Richter has been practicing veterinary medicine in the Bay Area since 1998. He took over Montclair Veterinary Hospital in 2002. In addition to its full array of health care services for domestic pets, the hospital is a drop-off point for injured wildlife.


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