Heart failure in dogs


Heart failure is one of the biggest killers of dogs. So when it comes to understanding heart disease, it pays to have your finger on the pulse.

The heart is responsible for pumping blood around the body, ensuring all the other vital organs can function properly. So when the heart has a problem, it is serious. Dogs can be born with cardiac defects, or they can develop as they grow older. Problems can lead to sudden heart failure, but with careful monitoring and treatment dogs can live with some heart conditions for many years.

Dr Mark Patteson, chairman of the Veterinary Cardiovascular Society, explained that heart disease was a common problem, but could be treated.

"About 10 per cent of dogs die from heart problems," he said. "But it's worth stressing that many more dogs will have heart disease but won't necessarily die from it. We've not found any way of stopping heart failure, but we can alleviate the symptoms so dogs live longer and retain a quality of life. It's important to ensure dogs maintain a level of exercise. Owners should make sure their dog has routine health checks once a year, so any heart murmurs can be picked up."

What heart problems are there?

There are four main ways in which your dog's heart can stop working properly:

Valvular disease

The heart has four separate chambers through which blood flows before being pumped to the rest of the body. Between these chambers are valves which ensure the blood moves in one direction. If the valves become damaged, blood is allowed to flow backwards in the heart, a process called regurgitation. This means the heart must work harder to pump blood around the body as it is fighting against the back flow. An estimated 75 per cent of all heart problems in dogs are in small breeds with leaky heart valves.


This is a deterioration of the heart muscle, which can become enlarged, flabby, or weak, making it less able to pump the blood. This is more common in large breeds of dog.

Pericardial disease

The pericardium is a sac that surrounds the heart, protecting it from trauma; it contains fluid to keep the heart moist. When excess fluid suddenly collects in the pericardium, because of a bleed or tumour inside it, it pressurises the heart so that it can no longer pump properly.


This is an irregular heartbeat; the dog's heartbeat might be too fast or too slow, or not in a regular rhythm. An arrhythmia can be a symptom of another condition, most commonly cardiomyopathy, or it can be a problem in itself. The heart is stimulated by electrical impulses which tell the heart when to beat. If there is a breakdown in these signals, it is known as a heart block.

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Spot the symptoms of heart disease in your dog

Often the first sign that your dog has a heart-related problem is a murmur picked up by the vet at a routine examination.

It's a good idea to get your dog vet-checked regularly, as he can look fine with no symptoms but have heart disease. A healthy heart makes a distinct ‘lub-dub' sound, which is clearly audible and in a regular rhythm. A murmur is an abnormal sound caused by changes in the blood flow through the heart. A murmur can be innocent, and cause no problems, or it can indicate your dog has heart disease.

Murmurs are graded on a scale of one to six depending on their loudness, although loudness does not always correlate to the severity of a problem. All heart conditions display similar symptoms that you can look out for, particularly if your dog already has a heart murmur, including:

  • Exercise intolerance.
  • Breathlessness.
  • Coughing.
  • Fainting.
  • Restlessness.
  • Lack of appetite.
  • Weight loss.
  • Tiredness and weakness.

Diagnosing a dog with heart failure

If your vet suspects your dog has a heart condition, he or she might refer you to a veterinary heart specialist for further tests and treatment. A cardiac ultrasound shows the heart in real time so a thick heart muscle or leaky valve can be detected.

An electrocardiogram (ECG) assesses the electrical activity of your dog's heart, revealing irregularities in his heartbeat. Radiographs show the size and shape of the organ and any fluid retention in the lungs. When your dog's heart begins to fail, the body detects the low blood pressure and releases hormones to retain fluids. This can be harmful in the long run, as fluid builds up in the lungs. Blood tests can also detect if the heart muscle has been stretched.

Treating a dog with heart failure

Treatments for a dog with a heart condition mainly consist of medication to help the heart cope better with its workload. There are drugs which stimulate the heart muscle to pump more strongly. Angiotensin-converting enzyme (ACE) inhibitors lower the workload by reducing the resistance to circulation. Diuretic medication encourages the production of urine, removing any build-up of fluid in the lungs. Your dog might need a combination of medication to treat his condition.

In rare situations, repairing your dog's heart requires surgery, such as the fitting of a pacemaker. There is research being done on replacing faulty valves, but this is a long way from being standard treatment. The majority of cases are treated through ongoing medical management.

As your pet gets older more medication is usually needed. The prognosis does vary but many dogs have a good quality of life for years with treatment and monitoring of the condition.