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Cardiac arrhythmias in dogs – Animal health

Cardiac arrhythmias in dogs - Animal health

Animal diseases

Cardiac arrhythmias in dogs – Animal health

Cardiac arrhythmias are abnormal heart rhythms that can occur in dogs. These disorders are classified according to the area of ​​the heart in which they originate: upper chambers, lower chambers, the heart area responsible for creating the heartbeat or electrical conduction system within the heart.

Each heartbeat originates as an electrical impulse in the upper right chamber of the heart (sinoatrial node). The impulse then travels through the upper chambers of the heart (atria) to an intermediate station (atrioventricular node) and finally to the lower chambers of the heart (ventricles).

The electrical impulse generates the typical pattern visible on an electrocardiogram (ECG). What disturbs the creation or transmission of the electrical impulse in the heart causes cardiac arrhythmia. Some are temporary and do not cause disease, but others are serious and can be life threatening.

Cardiac arrhythmias can affect dogs of any age, gender or breed. However, some breeds are more at risk than others of developing arrhythmias.

The giant dog breeds they are more prone to a type of arrhythmia known as atrial fibrillation, i.e. an abnormal rapid beat that originates in the atria. The Labrador Retriever is prone to supraventricular tachycardia, which is a rapid heart rate that originates above the ventricles. Doberman, Pinscher and Boxer they are prone to ventricular tachycardia, which is a rapid abnormal heartbeat that originates in the ventricles.

There sick sinus syndrome it is an anomaly affecting the sinoatrial node. It occurs most commonly in the following breeds: Dwarf Schnauzer, Dachshund, Cocker Spaniel and West Highland White Terrier. Spaniel, German Shepherds and Labrador Retriever are predisposed to some types of heart block.

There prognosis for animals with cardiac arrhythmias it depends on the type of arrhythmia, on the underlying cause of the arrhythmia and on the type and extent of any existing cardiac pathology.


Cardiac arrhythmia symptoms include:

  • Weakness
  • Collapse
  • Slow heart beat
  • Accelerated heart beat
  • Irregular heart rate
  • Respiratory difficulty
  • Lack of appetite


They should be done blood tests, complete blood count and biochemical profile included, to search for any underlying abnormalities. Some dogs may have anemia, an elevated white blood cell count or organ dysfunction. Some diseases, such as hypothyroidism, can be the cause of cardiac arrhythmias.

Cardiac arrhythmias are diagnosed by a electrocardiogram. The specific type of arrhythmia can be diagnosed by means of an electrocardiogram acquired with an oscilloscope or by a printout of the ECG trace. A thoracic radiography can help determine the possible presence of heart disease or heart failure.

What to do at home and prevention

There is no home care for abnormal heart problems in the dog, except that any medication prescribed by the veterinarian must be administered.

If you suspect that your dog has an abnormal heart rate or heart rate, contact your vet immediately.

Cardiac arrhythmias are difficult to prevent, but early diagnosis and treatment of predisposing causes can reduce the risk of developing arrhythmias.

Scientific explanation of canine arrhythmias

Normal heart rhythms begin in the cardiac sinus node, which is located in the upper right chamber of the heart. While cardiac sinus node anomalies are generally a consequence of a systemic disorder, such as hypothyroidism or hyperthyroidism, primary sinus disease is common and can lead to the onset of an arrhythmia known as sick sinus syndrome.

Other arrhythmias may occur outside the sinoatrial node and the most serious is atrial fibrillation. Arrhythmias resulting from the ventricles include premature ventricular contractions and ventricular tachycardia. Sometimes, more severe arrhythmias lead to heart failure and acute or chronic heart failure.

Cardiac arrhythmias can lead to one very low heart rate (potentially slow at 40 beats per minute, known as brachycardia), one very fast heart rate (potentially above 200 beats per minute, known as tachycardia) or one irregular heart rate. The types of arrhythmia that can arise are manifold. Some of the most common include:

  • Atrial fibrillation
  • Atrial tachycardia
  • Ventricular escape rhythm
  • Premature ventricular complex
  • Ventricular tachycardia
  • Ventricular fibrillation
  • First degree heart block
  • Second degree heart block
  • Third degree heart block

Often, canine cardiac arrhythmias are associated with underlying heart problems, such as dilated cardiomyopathy, congestive heart failure or congenital heart defects. In addition, a variety of other diseases or events can cause cardiac arrhythmias, including:

  • Hypothyroidism
  • Chronic lung disease
  • Anemia
  • Excessive dosage of some drugs, such as digoxin, narcotics, xylazine
  • Administration of anesthetic agents
  • High or low potassium blood levels
  • Cardiac neoplasms
  • hypoadrenocorticism (Addison’s disease)
  • Urinary obstruction
  • Lyme disease
  • Smoke inhalation
  • Head trauma
  • Hypothermia
  • Fear
  • Excitement
  • Ache
  • Hypotension
  • Volvulo-gastric dilatation
  • Spleen disorders
  • Serious infections


Some arrhythmias do not require treatment and spontaneously convert to normal. Other arrhythmias are severe and require treatment, the options of which include:

  • Medicines to control arrhythmia, treat underlying heart disease or normalize cardiac function in dogs. Medicines used include digoxin, diltiazem, propanol, enalapril, procainamide, lidocaine and atropine.
  • Some types of cardiac arrhythmias requireimplantation of a pacemaker to control the arrhythmia. Severe heart blocks often require a pacemaker to maintain normal heart rate and rhythm.
  • Dogs with congestive heart failure may need treatment with diuretic (for example, furosemide) and possibly nitroglycerin.
  • Dogs with underlying medical conditions often require prescribing additional medications. For example, dogs with hypoadrenocorticism may require steroid supplementation.

Follow up

The optimal treatment for your dog requires a combination of home and professional veterinary care. Follow-up can be crucial and include the following:

  • Administration of any veterinary drug prescribed in the manner indicated. Make sure to contact your veterinarian if you experience any problems in treating your dog.
  • Frequent veterinary evaluation (cardiac auscultation included – listening to the heart with a stethoscope).
  • Repeat the electrocardiogram to monitor your dog’s response to therapy.

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