Atrial Fibrillation in Dogs: Understanding the Rapid Heart Condition


The heart, a remarkable organ responsible for pumping blood throughout the body, comprises four chambers. The right and left ventricles, located at the bottom, propel blood to the lungs and the rest of the body, respectively. On the other hand, the right and left atria, situated at the top, accept blood from the general circulation and lungs, respectively. Harmonious contractions of these chambers enable smooth blood movement, incorporating oxygen exchange and carbon dioxide elimination, crucial for overall well-being.

What is Atrial Fibrillation?


In some cases, electrocardiograms (ECGs) performed before anesthesia reveal an abnormal heart rhythm known as atrial fibrillation. Atrial fibrillation manifests as rapid contractions or spasms specifically within the atria. Consequently, the ventricles may contract more rapidly than normal, leading to either regular or irregular rhythm. While atrial fibrillation often occurs as a secondary condition to heart disease, it can occur as a primary heart problem, particularly in larger breeds such as Irish Wolfhounds, Newfoundlands, and German Shepherds.

Causes of Atrial Fibrillation

Atrial fibrillation may arise without a specific cause, known as idiopathic atrial fibrillation. Alternatively, it can result from chronic heart valve disease, heart muscle disease (cardiomyopathy), or rare congenital heart disease present from birth.

Typical Signs of Atrial Fibrillation

Dogs with atrial fibrillation typically exhibit signs related to underlying heart disease. If congestive heart failure occurs, the heart struggles to pump blood effectively, leading to inadequate oxygen supply to tissues and disrupted fluid balance. Consequently, the dog may experience exercise intolerance, exhaustion with minimal exertion, coughing, and difficulty breathing. When a veterinarian listens to the dog’s heartbeat using a stethoscope, the irregular heart rhythm caused by atrial fibrillation may sound like an additional heart sound. Additionally, a condition called pulse deficit may be observed, where fewer pulses are felt in an artery compared to what is heard through a stethoscope.

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Treatment Options for Atrial Fibrillation

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To manage atrial fibrillation in dogs, medications that slow down the conduction of electrical signals between the atria and ventricles are commonly used. These medications include beta-adrenergic blockers like atenolol (Tenormin®) and calcium-channel blockers such as diltiazem (Cardizem®, Dilacor XR®, Tiazac®, Diltia XT®, Taztia XT®, Dilt-XR®). Digoxin (Lanoxin®, Lanoxicaps®, Toloxin®, Digitek®, Digox®) is another option. It is important to note that dogs with atrial fibrillation often have underlying heart disease, necessitating a comprehensive medical management approach. Treatment for congestive heart failure includes medication to alleviate excess fluid, control hypertension (if present), and improve heart function. In some cases, cardioversion, a specialized treatment involving electrical or drug methods, can be attempted, but it usually requires referral to a heart specialist. Additionally, a tailored diet may be recommended, potentially including a mild to moderate restriction of sodium for dogs experiencing congestive heart failure.

Monitoring and Follow-Up

Monitoring heart rate closely is crucial in managing atrial fibrillation, along with follow-up ECGs to assess the progress of treatment. Radiographs (X-rays) of the chest and heart ultrasounds can also aid in evaluating heart health. For dogs undergoing digoxin therapy, close monitoring of blood levels is essential to ensure no additional complications arise. Over time, heart function may deteriorate, leading to congestive heart failure that cannot be effectively managed. In such cases, euthanasia may be the appropriate decision. However, with proper medical management, many dogs can live a fulfilling life, especially if they do not have preexisting structural heart disease or heart failure.

Remember, if you suspect your dog may have atrial fibrillation or any other heart condition, seeking guidance from a qualified veterinarian is always the best course of action.

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