Atrial Fibrillation in Dogs: Causes, Symptoms & Treatment Options

Atrial fibrillation (AF) is a heart condition quite common in dogs, causing an irregular or fast heartbeat, medically known as an arrhythmia. This article explores what atrial fibrillation is, its causes, symptoms, diagnosis, and the latest treatment options available in the UK in 2025, helping you better understand and care for dogs with this condition.

What is Atrial Fibrillation in Dogs?

Atrial fibrillation occurs when the atria, the upper chambers of the heart, do not contract properly but flutter erratically. Fortunately, the larger lower chambers, the ventricles, continue to pump blood, albeit often with a very fast and chaotic heartbeat. This irregular rhythm reduces the heart’s efficiency, causing symptoms that impact your dog’s quality of life.

Causes of Atrial Fibrillation

There are two main types of AF in dogs:

• Primary AF: Rare and mostly seen in large or giant breeds such as Deerhound puppies. It arises due to the large size of the heart chambers which disrupts the electrical signals despite the heart muscle being healthy.
• Secondary AF: More common and usually a complication of another heart disease, particularly dilated cardiomyopathy (commonly seen in breeds like Dobermanns) and congestive heart failure. This form tends to cause a very fast, inefficient heartbeat and is associated with a more serious prognosis.

Recognising Symptoms

Dogs with AF may show the following signs, often related to the type of AF:

• Exercise intolerance — dogs tire quickly and become breathless easier than healthy dogs.
• Increased respiratory rate — fast or laboured breathing, often the first symptom noticed.
• Coughing and fainting — which may result from inadequate oxygen supply.
• Blue gums — an indicator of poor oxygenation in the blood.
• Sudden collapse or, unfortunately, sudden death may occur especially in severe Secondary AF cases with underlying cardiomyopathy.

How is Atrial Fibrillation Diagnosed?

A vigilant vet can hear the characteristic irregular, chaotic heart rhythm using a stethoscope. To confirm AF and understand its severity and cause, more detailed tests are needed:

• Electrocardiogram (ECG): Records the electrical activity of the heart and provides a definitive diagnosis.
• Holter Monitoring: A 24-hour (or longer) ECG recording that monitors heart rhythm during normal activity, offering a more accurate assessment of heart rate control.
• Echocardiogram (Heart Ultrasound): Assesses heart structure and can identify underlying diseases affecting heart function.

Treatment and Management

Current veterinary consensus in the UK focuses mainly on controlling the heart rate to improve your dog's comfort and longevity:

• Primary AF: In some cases, if diagnosed early (within four months), referral to a veterinary cardiologist can allow cardioversion, a procedure aiming to restore a normal heart rhythm.
• Secondary AF: Treatment emphasises medical management with drugs such as digoxin and diltiazem to slow the heart rate and improve pump efficiency. Beta-blockers may also be used cautiously, especially if there is congestive heart failure.
• In rare cases where medication fails, advanced procedures like radioablation of the AV node with pacemaker implantation may be considered in specialist centres.

Regular monitoring, particularly with 24-hour Holter recordings, helps adjust medications and assess effectiveness, aiming for a target heart rate below 140 beats per minute, or ideally less than 125 bpm for better outcomes.

Why Early Veterinary Attention Is Vital

Prompt diagnosis by your vet is essential for managing AF effectively. Early intervention can slow progression, improve quality and length of life, and help avoid serious complications. If your dog shows any signs like breathlessness, coughing, fainting, or exercise intolerance, consult your vet swiftly.

Conclusion

Atrial fibrillation in dogs is a significant heart condition commonly linked to other heart diseases. With advances in veterinary cardiology, diagnosis with ECG and Holter monitoring and management focusing on rate control provide hope for affected dogs. Responsible dog owners should seek early veterinary assessments if symptoms arise and collaborate closely with their vet for ongoing management. This approach ensures the best possible care and comfort for dogs living with AF.