Atrial fibrillation, or auricular fibrillation (AFib), is one of the most common cardiac arrhythmias in dogs, but it remains largely silent: many dogs show no visible symptoms until an advanced stage, especially when it is not yet associated with an underlying heart disease. Understanding what it is, which breeds are most at risk, and how to detect it before clinical signs appear allows for early action — this is precisely what regular monitoring of heart rate and rhythm at home enables.
What is atrial fibrillation in dogs? #
Atrial fibrillation is a heart rhythm disorder in which the atria of the heart contract rapidly and disorganized, instead of following a regular rhythm. Result: the ventricles receive irregular electrical signals and also contract erratically, making the pulse “irregularly irregular” upon auscultation — a rhythm that veterinary cardiologists at VCA Animal Hospitals describe as the sound of “sneakers tumbling in a dryer.”
There are two main forms:
- Idiopathic atrial fibrillation: it occurs without associated heart disease, most often in large to giant breed dogs. It is an isolated electrical anomaly, without heart enlargement.
- Secondary atrial fibrillation: it appears as a complication of an already present heart disease — most often a dilated cardiomyopathy (DCM) or advanced mitral valve disease. It is the most common form in practice.
Which breeds are most predisposed? #
| Breed | Most Common Type of AFib | Specificity |
|---|---|---|
| Irish Wolfhound | Idiopathic | Most studied breed on the subject; idiopathic AFib is relatively common |
| Doberman | Secondary (to DCM) | AFib often appears as a complication of an already established dilated cardiomyopathy |
| Newfoundland | Idiopathic or Secondary | Also affected large breed |
| Rottweiler | Idiopathic or Secondary | Documented predisposition in large breeds |
| German Shepherd | Idiopathic | Large breed also represented in studies |
| Bernese Mountain Dog | Idiopathic | Large breed also represented in studies |
According to data collected by the Central Canine Society on idiopathic atrial fibrillation, the Irish Wolfhound remains the most studied breed on the subject, with a favorable prognosis reporting an average survival of 6 to 8 years after diagnosis in the absence of associated heart disease.
In general, the larger the dog, the higher the risk of atrial fibrillation — idiopathic or secondary. This is why it almost exclusively affects large to giant breeds, unlike diseases like mitral valve which concern smaller breeds more. This link with breed size is also found in the normal heart rate benchmarks by breed: the larger the dog, the lower its resting heart rate naturally is, making a rhythm irregularity all the more detectable in its monitoring.
What symptoms should alert? #
Atrial fibrillation can remain silent for a long time, especially in its idiopathic form and when the ventricular rate remains moderate. When signs appear, they most often include:
- intolerance to exercise or unusual fatigue after previously well-tolerated exercise;
- syncope (brief loss of consciousness), related to insufficient blood flow to the brain;
- cough or respiratory discomfort, if fluid accumulation occurs (a sign of progression to heart failure);
- an irregular pulse, noticeable upon palpation or detected during veterinary auscultation.
These signs, especially when combined, justify a prompt consultation — all the more so in a predisposed breed or a dog already monitored for heart disease.
How is atrial fibrillation diagnosed? #
The diagnosis is based on the electrocardiogram (ECG), the only test that can confirm AFib with certainty and assess the ventricular rate. A Holter (24-hour ambulatory ECG) is sometimes used to capture intermittent episodes. Echocardiography remains essential: it distinguishes idiopathic AFib (normal-sized heart) from AFib secondary to dilated cardiomyopathy or valvular disease (enlarged heart).
What treatment and prognosis? #
Management mainly depends on the ventricular rate and the presence or absence of associated heart disease:
- If the fibrillation is slow and there is no heart enlargement, sometimes no treatment is necessary — simple regular monitoring suffices.
- Beyond a high ventricular rate (over 150 beats per minute approximately), a combination of digoxin and diltiazem is generally implemented to slow electrical conduction. Beta-blockers (atenolol, sotalol) may also be used depending on the case.
- When AFib is secondary to cardiomyopathy or valvular disease, treating the underlying heart disease remains the priority.
The prognosis for isolated idiopathic atrial fibrillation is generally favorable, with an average survival of 6 to 8 years after diagnosis. The prognosis for the secondary form mainly depends on the heart disease causing the arrhythmia.
Can atrial fibrillation be detected before the first symptoms? #
This is precisely the interest of regular home monitoring. Atrial fibrillation results in an irregular heart rhythm — a parameter that the Biotracker is designed to detect continuously, even during sleep, thanks to its atrial fibrillation risk estimation algorithm.
This monitoring does not replace ECG or echocardiography, which remain the only tests capable of confirming a diagnosis, but it allows for detecting a rhythm anomaly between veterinary visits — especially in the at-risk breeds listed above. And as with all diseases: the earlier the symptoms are detected, the better the management and chances of treatment.
FAQ #
Is atrial fibrillation serious in dogs? It depends on the form. Isolated and without associated heart disease, it often remains silent and with a good prognosis. Secondary to cardiomyopathy or valvular disease, its severity mainly depends on the underlying disease.
Which breeds are most at risk for atrial fibrillation? Large to giant breeds: Irish Wolfhound, Doberman, Newfoundland, Rottweiler, German Shepherd, Bernese Mountain Dog. In Dobermans in particular, it most often appears as a complication of an already established dilated cardiomyopathy. The Boxer, often cited among “at-risk cardiac” breeds, mainly develops ventricular arrhythmias related to ARVC (arrhythmogenic right ventricular cardiomyopathy) — a different rhythm disorder from atrial fibrillation.
How do I know if my dog has atrial fibrillation? Only an electrocardiogram can confirm it. Home monitoring of heart rate and regularity, with a connected collar for example, can alert to an irregularity to be checked by a veterinarian.
Can atrial fibrillation be treated? It cannot be “cured” in the strict sense, but it can be managed: slowing the ventricular rate with medication if necessary, treating the underlying heart disease if applicable, and regular monitoring.
What is the difference between atrial fibrillation and dilated cardiomyopathy? Dilated cardiomyopathy (DCM) is a disease of the heart muscle that weakens and enlarges. Atrial fibrillation is an electrical rhythm disorder of the heart. The two are linked in certain breeds (the Doberman often develops AFib as a complication of its DCM), but remain two distinct pathologies.
Can stress or exercise trigger atrial fibrillation? In dogs already affected by underlying heart disease, intense physical effort can, in some cases, trigger an episode of atrial fibrillation through a mechanism opposite to what one might expect: an excessive vagal reflex just after exertion, which abruptly slows the heart before causing the AFib episode — this was documented in a study published in the Journal of Veterinary Cardiology in dogs presenting with syncope. However, no solid data directly links stress or excitement to an increased risk of atrial fibrillation in dogs.