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Heart Beat Problems (Fibrillation and Flutter) in Dogs

Atrial Fibrillation and Atrial Flutter in Dogs

The canine heart consists of four chambers: two atria (singular: atrium) and two ventricles. Between each atrial and ventricular pair, there are valves on both the left and right sides. The tricuspid valve separates the right atrium and right ventricle, while the mitral valve separates the left atrium and left ventricle. The heart operates with remarkable synchronization among these chambers, resulting in a consistent rhythmic pattern.

However, both atrial fibrillation and atrial flutter disrupt this rhythm, causing a loss of synchronization between the atria and ventricles. These conditions stem from rhythm disturbances originating in the upper chambers of the heart, namely the atria. Atrial flutter often serves as a precursor to atrial fibrillation. In atrial flutter, an untimely electrical impulse emerges in the atria, leading to a faster-than-normal heart rate that may be regular or irregular in frequency. On the other hand, atrial fibrillation involves a quivering contraction of the heart muscles, resulting in a rapid and abnormal heart rhythm, also known as arrhythmia. In atrial fibrillation, the atria beat chaotically, causing irregular rhythms in the ventricles as well. Atrial fibrillation can occur with or without underlying heart disease. Electrocardiogram (ECG) readings, which measure the heart’s electrical activity, reveal distinct patterns for atrial fibrillation and atrial flutter.

Symptoms and Types

Atrial fibrillation presents in various forms:

  • Primary atrial fibrillation: Occurs without any identifiable underlying cardiac disease.
  • Secondary atrial fibrillation: Associated with severe underlying cardiac conditions such as congestive heart failure (CHF).

Furthermore, it can be classified based on its duration and responsiveness to treatment:

  • Paroxysmal atrial fibrillation: Characterized by periodic, recurrent episodes lasting less than seven days, with the heart spontaneously returning to its normal rhythm.
  • Persistent atrial fibrillation: Lasts for more than 48 hours and requires intervention to restore normal rhythm.
  • Permanent atrial fibrillation: An ongoing condition that cannot be successfully treated to restore normal rhythm.

Symptoms of atrial fibrillation often indicate an underlying health issue like congestive heart failure (CHF). Common symptoms include:

  • Rapid or irregular heartbeat (galloping heart)
  • Difficulty exercising (exercise intolerance)
  • Weakness
  • Persistent cough
  • Difficulty breathing (dyspnea)
  • Rapid breathing (tachypnea)
  • Lethargy
  • Rarely, loss of consciousness (syncope)


Atrial fibrillation can be caused by various factors, including:

  • Chronic heart disease affecting the valves
  • Heart enlargement
  • Cardiomyopathy (disease of the heart muscle)
  • Congenital heart defects
  • Presence of tumors (neoplasia)
  • Toxicity from medications like digoxin, often used in treating heart conditions
  • Occurring as a consequence of congestive heart failure (CHF)
  • In some cases, the cause may not be identified.


Following a thorough assessment of your dog’s medical history, including background health information and symptom onset, your veterinarian will conduct a comprehensive physical examination. Laboratory investigations will involve a complete blood profile, including a biochemical profile, complete blood count, and urinalysis. While these tests may not specifically pinpoint the disease, they can provide valuable insights into your dog’s overall health status and detect any concurrent conditions. Additional diagnostic procedures may include echocardiography (ECG), X-ray imaging, and color Doppler, aiding in the identification and assessment of any underlying heart ailments, including their type and severity.


Once your veterinarian has determined the severity of the atrial flutter or fibrillation in your dog, as well as whether any underlying heart condition like CHF is contributing to the arrhythmia, treatment will be initiated. If the heart rate is excessively rapid, medication will be administered to slow it down. In cases where no underlying heart disease is identified, the focus will be on restoring a normal heart rhythm and synchronizing the sinoatrial node with the atrioventricular node (AV). However, if the fibrillation persists chronically (for more than four months), treatment success rates may decrease, often leading to recurrent issues. In such cases, electrical shock therapy may be employed to restore normal rhythm. Additionally, if concurrent cardiac issues like CHF are present, treatment will also involve addressing these conditions and stabilizing the heart rhythm.

Living and Management

Adhere to your veterinarian’s instructions regarding your dog’s diet, exercise, rest, medication, and overall health management at home. Recurrence of atrial fibrillation, particularly in cases of primary atrial fibrillation, is possible, especially in chronic conditions. Monitor your dog’s well-being closely and promptly contact your veterinarian if you observe any unusual symptoms. In instances of severe cardiac conditions like CHF, diligent commitment and care will be essential from your end for administering at-home treatment and management. Maintaining a detailed diary of events and maintaining regular communication with your veterinarian throughout the treatment process will facilitate monitoring your dog’s progress and promptly addressing any emerging issues.

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