Canine Acquired Heart Disease


Canine Acquired Heart Disease

Heart disease leads to less effective pumping of blood around the body. When the supply of blood to the tissues no longer meets the needs of the body, we call the condition heart failure. In heart failure, due to changes in blood pressure in the body, fluid can build up in the lungs or in the abdomen.

Heart disease is common in middle aged and older dogs. Although it is not something that can be cured, it is something that we can manage with careful exercise and diet, and the use of medicines supplied by your vet.

Young dogs may also suffer from heart conditions, but these are more often congenital in origin, having been present since birth. Different breeds are predisposed to different congenital heart conditions, some may run in families and others can be carried genetically from a parent to their offspring. This leaflet does not deal with these less common conditions of younger dogs, and focuses on the acquired heart diseases only.


Heart failure can be present in our pets for a long period of time before they show any signs of a problem. The body is good at compensating for any slight changes to blood flow and heart contraction early on, but eventually clinical signs will develop.

Regardless of the cause of heart failure, the most common signs that we notice in animals are the same:

  • Decreased enthusiasm and ability to exercise
  • Muscle weakness in the back legs
  • High heart rate/breathing rate
  • Persistent cough, often worse in the evenings
  • Episodes of collapse, more often during exercise or excitement
  • Weight loss or a loss of body condition, or poor appetite


Two main causes of acquired heart failure are identified in dogs:

1. Valve Problems

Valve problems can affect any breed of dog, but mostly affect the SMALL BREEDS. Most commonly the mitral valve, located in the left side of the heart, is affected. The valve does not close properly, which allows abnormal flow of blood through the heart in the opposite direction to normal. This leaking of blood over a long period of time can cause changes in the structure of the heart muscle, and means that less blood than normal is pumped out of the heart with each beat. Eventually, heart failure begins.

Most common valve problem: MITRAL VALVE DISEASE (MVD)

2. Heart Muscle Problems

Muscle problems can affect any breed of dog, but mostly affect the LARGE BREEDS. Most commonly, the heart muscles weakens and slackens, becoming weaker and less effective at pumping blood around the body. This causes the heart to enlarge, but as it is weaker, less blood is pumped with each beat. Eventually, this leads to heart failure.

Most common heart muscle problem: DILATED CARDIOMYOPATHY

More rarely, the rhythm of the heart may be affected and lead to poor pumping of blood. Sometimes, this can occur with a sudden onset and without previous problems having been noticed.


A thorough physical examination of your dog, together with the history provided by owners, can provide very valuable information on any suspected heart problems. Listening to the heart using a stethoscope can identify abnormal heart sounds (murmurs) or rhythms. These are a common early warning sign of heart disease, and may be picked up at annual health checks or booster vaccinations. Further tests may include:

Radiography (X-Rays): can show enlargement of the heart or fluid build up in the lungs.
ECGs: provide information on the electrical activity within the heart and can diagnose various rhythm disturbances. Also gives information on size of heart.
Ultrasound (Echo): like a pregnancy scan in humans, this technique uses high frequency sound waves to show an image on screen of the movement of the heart and valves, and can sometimes provide a conclusive diagnosis of the cause of heart failure.


Sometimes, heart disease is picked up very early on, using clues provided by physical examination or hearing abnormal heart sounds at the vets. If there are no clinical signs of heart failure noticed, then there is no proven benefit in treating dogs.

If clinical signs of heart failure are present, treatment must be started to prevent deterioration of the heart, to increase quality of life, and increase length of life. Untreated, dogs with heart failure deteriorate quickly and the disease may be fatal.

Treatment aims to do two things:

Increase the strength of contraction of heart muscle, making pumping of blood more efficient and meeting the needs of the body.

Decrease the fluid build up caused by heart failure, getting rid of fluid from the lungs or the abdomen.

Treating heart failure cannot cure the underlying disease, but does increase quality of life and longevity, and decreases the clinical signs of heart failure. Usually, doses of medication are twice daily. After finding the right dose of medication, three monthly check ups with your vet are all that are required, unless further problems develop or you have any concerns.

Good websites to read are: and

Should you wish to discuss any of these issues in more detail, please consult your veterinary surgeon.