"Atrial Fibrillation in dogs – can anything be done?

"Atrial Fibrillation in dogs – can anything be done?

Health & Safety

This is a heart condition and it is quite common in dogs. It causes an irregular heartbeat or a fast heartbeat - an arrhythmia. Looking after a dog with this condition is not always clear-cut, so in this Pets4Homes article, we’ll look deeper into the condition, causes, treatment in more detail.

So, what is it?

Atrial fibrillation occurs because the atria which is that part of the heart, do not contract properly as they should do. Instead, they tend to spasmodically flutter. Luckily the lower chambers of the heart, the ventricles, are bigger and continue to work by contracting and pumping blood around the body. If they didn’t work this way, the problem with the atria could be fatal. Even though the ventricles continue to pump, the heart is often very fast and again slightly chaotic.

Why does it happen?

In atrial fibrillation, there are two main reasons why it happens, and because atrial fibrillation is commonly known as AF, the causes also take on those initials. The two main causes of AF are:

  • Primary AF
  • Secondary AF

So not very exciting names, but quite different types of problem. Looking at them closely you can see why!

Primary AF

This condition is actually quite rare and tends to only happen to large, or which is normally the case, giant breed dogs. It is generally to do with the size of the heart, as this primary AF can happen in an otherwise healthy heart muscle. The reason it affects dogs with larger hearts is that the chambers, both top, and bottom are so big, that the electrical pulse and signals in them can get disrupted. If they were human they would probably be fitted with a pacemaker! Because the chambers are so large and take longer to fill and contract the heartbeat normally remains quite low. This is why in primary AF the heart rate is often called slow AF.

Secondary AF

This is the much more common type of atrial fibrillation. It is called Secondary AF because it is, in fact, a secondary effect and is commonly caused by another heart disease. The main two are dilated cardiomyopathy (often seen in Dobermans) and CHF otherwise known as Congestive Heart Failure. Secondary AF may sound better than primary AF, however, it is usually much more serious. In Secondary AF the heart muscle is already damaged through another disease, but the heart rate in this type of AF is usually very fast. This in itself can cause extra issues as an abnormally fast heart rate reduces the efficiency of the heart by pumping blood without the heart filling correctly.

So, what do I look for?

For most dogs with AF, there is an underlying cause - a heart condition that is making the AF happen. However, it’s not always the case, especially in Primary AF. If there is no apparent underlying disease, the heart works albeit erratically but does not use all the four chambers, only the two ventricles. In this case, the most common thing that will be seen is exercise issues, where the dog quickly runs out of energy and breath. This happens quicker than it would do in a healthy dog. The heart is basically misfiring.

Dogs that have Secondary AF always have an underlying cause, and it is from this condition you might see a range of symptoms including:

  • Increased respiratory rate - where the dog breathes fast (this can be the first symptom you see).
  • Coughing - again related to the breathing.
  • Fainting - from lack of oxygenated blood.
  • Unable to exercise - as any over movement can cause the above.
  • Blue gums - from lack of oxygenated blood in the system.

Sadly, sometimes the first symptom can be the heart stopping (not unusual in cases of Secondary AF in dilated cardiomyopathy). The results in the sudden death of the dog.

How will my vet diagnose the condition?

Strangely it doesn’t take much to detect the condition - only a stethoscope. A heart that has the AF condition will sound like a mess! AF produces random heartbeats that are totally erratic and can be heard clearly. Some vets even offer the owner to listen, so they can understand the problem and that it needs treatment.

Some vets like to confirm that the condition is indeed AF as there are other types of irregular, fast heartbeats. Confirmation can also help them understand the root cause of the problem. The most accurate way to achieve this is by measuring the electrical activity in the heart, a procedure called ECG. The best scenario for testing this electrical activity is over 24 hours. Using a piece of equipment called a Holder Monitor can do this, and there are harnesses that fit the equipment to the dog, so they tolerate it very well.

The main cause of the condition can also sometimes be determined by a heart scan, and with dogs suffering from AF, many vets will also use this test.

So what treatment is there to help?

There is a treatment for both Primary and Secondary AF. Amazingly if a dog has had Primary AF for a short time (less than four months) they can be referred by a first option vet, to a veterinary cardiology specialist. A specialist of this type can perform a procedure that can reverse the heart condition, and bring the heart back to a normal rhythm. This procedure is known as cardioversion.

In some cases of Primary AF, the vet may also try drug therapy, which can sometimes be effective, without the need for referral.

It is a different story for dogs with Secondary AF as cardioversion is seldom successful. For Secondary AF the dog is normally managed medically with heart medication to slow the heart rhythm, reducing the heartbeat speed and erratic nature of it. Drugs such as digoxin (a human heart drug) are often used for this purpose. The sole aim of managing this Secondary AF condition is getting the heart to work more effectively.

Secondary AF does not give a good outlook for the dog, due to the nature of the problem, but with drugs, the condition can be managed. According to the severity of the cause, the management can be from months to years.


Atrial fibrillation is a common but, worrying disease. If you have any concerns that your dog might be showing signs of heart disease, please speak to your vet urgently. The quicker the diagnosis, the better, and any treatment can be started.

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