Heart Disease In Dogs and Cats

Dog-and-Cat-Wallpaper-teddybear64-16834783-1280-800Just like people, our pets are susceptible to heart problems and today’s pets are living longer than their predecessors so, as a result, heart disease is becoming increasingly more common in dogs and cats. These problems may be present from birth, or may happen as our pets get older. Heart problems can be divided into two groups

  1. Congenital: These conditions can be caused as the embryo develops in the mother’s womb or may be a hereditary (passed on from the mother or father). In this case the problem is present at birth but signs may go undetected for a while.
  2. Adult onset: These conditions occur as a result of damage to the heart which prevents it functioning properly, or they can be hereditary conditions which do not present until the animal is fully grown.

How does the heart work?
Like all mammals, dogs and cats have a four chambered heart which is made up of three layers.

  1. Pericardium – a fluid-filled sac that surrounds the heart
  2. Myocardium – a middle layer of muscle
  3. Endocardium – the inner lining

The right atrium and left atrium are the upper chambers of the heart and the right ventricle and left ventricle are the lower chambers. A muscular wall called the septum separates the right and left sides of the heart. Each of the chambers has valves in order to make sure that the blood flows in the correct direction.

  • Tricuspid valve is at the exit of the right atrium
  • Mitral valve is for the left atrium
  • Pulmonary valve is at the exit of the right ventricle
  • Aortic valve is at the exit of the left ventricle.

The different sides of the heart have different functions.

  • On the left side, the upper chamber fills with oxygen-rich blood from the lungs. This is pumped via the lower chamber into the aorta and out to the body to provide cells with the crucial oxygen they need.
  • On the right side, the upper chamber fills with oxygen-depleted blood from your body and pushes it via the lower chamber and the pulmonary artery back to the lungs. Here blood picks up oxygen and releases carbon dioxide.

The heart muscle contracts in two stages to squeeze blood out of the heart.

  • In the first stage the upper chambers (atria) contract at the same time, pushing blood down into the lower chambers (ventricles). Blood is pumped from the right atrium down into the right ventricle and from the left atrium down into the left ventricle.
  • In the second stage, the lower chambers contract to push this blood out of the heart to either the body via your main artery (aorta) or to the lungs to pick up oxygen.

The heart then relaxes. Blood fills up the heart again, and the whole process, which takes a fraction of a second, is repeated.


How do I keep my pet healthy?
Keeping your pet healthy is not only a great way of helping to prevent heart disease but it can also help pets that have been diagnosed with heart problems to stay healthier for longer.

  • Watch your pet’s weight; being overweight makes the heart work harder. You are responsible for the amount of calories your pet eats and it is down to you to keep your pet at a healthy weight!
  • Make sure your pet gets regular exercise; this will improve overall health and fitness in your pet and prevent excess weight gain.
  • Watch for the signs of heart disease (listed below).
  • Take your pet for annual check-ups with the vet. Early detection will improve your pet’s chances.
  • Feed a well-balanced, healthy diet. This is as good for your pet’s heart as it is for yours.
  • Know your breed. Some dog breeds (such as the Cavalier King Charles Spaniel, Poodle, Boxer, and Bulldog), and cat breeds (such as the Persian, Maine Coon, Siamese and Ragdoll) are more susceptible to heart disease than others.
heart breeds

Bulldogs, Persians, Cavaliers and Siamese can all suffer with heart problems

Signs that your pet may have a heart problem
Clinical signs may vary in animals and will depend on the severity of the problem. Most animals don’t show clinical signs until the heart problem is quite advanced, because in the initial stages the body learns to cope with the changes, and cats especially are very good at hiding illnesses. These are some of the most commonly seen signs

  • Tiredness
  • Reluctance to exercise
  • Increased respiratory effort and rate (heavy breathing/panting)
  • Weight loss
  • Collapse/fainting
  • Pain
  • Stunted growth (kittens and puppies)
  • Coughing (usually only in dogs)
  • Behavioural changes

Common heart problems that may affect dogs and cats

Heart Murmur: This is caused by turbulent or fast blood flow within the heart or associated vessels. There are lots of causes for heart murmurs; some are not associated with any structural heart disease and can be caused by stress or high temperatures, other murmurs can be caused by abnormal blood flow associated with a variety of cardiac diseases, including abnormal heart valves and different congenital defects. Murmurs are commonly heard in young puppies and kittens and if they are not associated with heart disease they often disappear in a few months.

Valvular Disease/Insufficiency: Heart valves normally form a perfect seal when closed. However, in valve disease one or more of these valves “leak,” allowing blood to be pumped backwards. This is the most common form of heart disease in dogs and occurs mostly in the smaller breeds.

Bacterial Endocarditis: This is caused by a bacterial infection of the heart valves or of the membrane lining the cavities of the heart, leading to valvular insufficiency.

heart valves

Heart valves

Dilated Cardiomyopathy: The muscle of the heart becomes thinner and gradually weaker, causing the heart chambers to stretch, which prevent it from pumping blood around the body as effectively as it should. DCM affects mainly middle-aged large and giant breed dogs and some spaniels. Cats and small breeds of dog are occasionally affected

Hypertrophic Cardiomyopathy: Characterised by the inward thickening of the heart muscle, resulting in a reduction of chamber volume, which means that the heart pumps less blood around the body. This is the most common form of heart disease found in cats.

Restrictive Cardiomyopathy: Caused by fibrosis (scarring) of the heart muscle, which results in a chamber that can no longer expand in the normal way.

Cardiomyopathy diagram


Congestive Heart Failure: This is unfortunately the usual end result of most heart conditions in dogs and cats. As the heart loses its ability to pump blood around the body properly it becomes congested, resulting in fluid build-up in the abdomen and chest cavities, which lead to abdominal enlargement and interference with the other organs. If fluid builds up in the lungs it results in coughing and breathing difficulties.

Diagnosing heart problems

This will vary from patient to patient and will also depend on the clinical signs, but usually two or more of the following tests are performed

  • Auscultation: The vet will listen to your pet’s heart with a stethoscope to detect any murmurs or irregular rhythms.
  • Ultrasound: Allows the vet to examine the heart while it is in motion. It can be used to measure the chambers and walls of the heart and see the heart valves, so can provide a very accurate diagnosis.
  • X-rays: these can show your vet if the heart is enlarged or has changed shape and show if there is any fluid in chest or abdominal cavities.
  • Electrocardiogram (ECG): Shows the electrical activity of your pet’s heart to measure and diagnose abnormal heart rhythms
  • Blood and urine test: These are done to assess general health and ensure that there are no problems with other organs in the body, for example the kidneys or liver.

diagnostic tests

Treatment for heart problems

In early stages of heart disease there may be no signs and your pet may just need to be checked regularly by your vet. If signs develop these can be treated, however, in most cases heart disease does get worse and treatment will only slow down the rate of disease progression. Treatment can include

  • Changes to your pet’s lifestyle, for example more controlled exercise and activities to prevent over exertion.
  • Medication to improve the strength of the heart beat or change the heart rate and, if necessary, to help remove excess fluid from the chest and abdominal cavities.
  • Dietary changes may be recommended by your vet depending on the type of heart disease present.
  • Some congenital heart defects can be corrected by surgery so your vet may recommend this.

Castle Vets reading hope that you found this article informative and interesting. If your pet shows any of the above signs you should contact your vet as soon as possible.

If you have any questions about heart problems you can contact the surgery for an appointment.

One thought on “Heart Disease In Dogs and Cats

  1. Pingback: Heart Disease In Dogs and Cats | Castle Vets Reading

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