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Irregular Heartbeat in Dogs

Sinus Arrhythmia in Dogs

Irregular heartbeat in dogs, known as sinus arrhythmia, occurs due to abnormal variations in the heart’s rhythm. This can manifest as the heart beating too fast, too slow, or skipping beats. The sinoatrial node (SA Node or SAN), often referred to as the sinus node, serves as the heart’s pacemaker, initiating electrical impulses that regulate its beating. These impulses are influenced by the nervous system, with the vagus nerves decreasing the heart’s spontaneous discharge rate and sympathetic stimulation increasing it. Respiratory and cardiac centers also play a role, with inhalation accelerating heart rate and exhalation having the opposite effect.

Sinus arrhythmia is also influenced by reflexes involving lung stretch receptors, pressure-volume sensory receptors in the heart and blood vessels, and chemical factors in the blood. While sinus arrhythmia typically doesn’t affect blood flow, severe cases may lead to fainting if an escape rhythm doesn’t kick in.

Although arrhythmia is common in dogs and may not always indicate a serious problem, it’s essential to have it evaluated by a veterinarian. Certain breeds, particularly brachycephalic breeds such as bulldogs, lhasa apsos, Pekingese, pugs, shar-peis, shih tzus, and boxers, seem to be predisposed to sinus arrhythmia.

Symptoms and Types

Symptoms and types of irregular heartbeat in dogs typically include a heart rate that is either too fast, too slow, or irregular (skipping beats). This irregular heartbeat, also known as arrhythmia, may lead to physical weakness if the pauses between beats are excessively long. In rare cases, loss of consciousness can occur, though these side effects are uncommon. Generally, symptoms are more prevalent in nonrespiratory forms of arrhythmia compared to respiratory forms.


  • Normal cyclic changes in the vagus nerves linked to respiration, where heart rate rises during inspiration and falls during expiration.
  • Underlying conditions that elevate vagal tone, such as high intracranial pressure, gastrointestinal disease, respiratory disease, cerebral disorders, digitalis toxicity, and congestive heart failure.
  • Brachycephalic conformation.
  • Digoxin therapy (digitalis).
  • Any disease impacting the vagus nerves.


Diagnosing irregular heartbeat in your dog involves a comprehensive physical examination by your veterinarian, considering the background history of symptoms and any potential incidents leading to the condition. Providing a detailed history of your dog’s health and when symptoms started can offer valuable insights to your vet, aiding in the identification of underlying disorders or other affected organs.

Electrocardiogram (ECG or EKG) recordings are commonly used to assess the heart’s electrical currents, detecting any abnormalities in cardiac electrical conduction that may contribute to irregular heartbeats. Additionally, X-rays of the head and neck may be conducted to evaluate for abnormal anatomical structures that could predispose your dog to airway issues. If upper airway disease is suspected, your veterinarian may perform a minimally invasive procedure known as pharyngoscopy or laryngoscopy. This involves inserting a tubular device with a camera into the respiratory tract (pharynx and larynx) to visually inspect the area.


Treatment for irregular heartbeat in dogs typically focuses on addressing symptomatic slow heartbeat or underlying causes. Hospitalization may be necessary if your dog experiences respiratory distress until stability is achieved. Activity restrictions may be advised based on specific conditions (e.g., brachycephalic animals may need limited exercise, particularly in hot temperatures). If your dog is overweight, your veterinarian may recommend caloric restriction to prevent airway compromise. Medications will only be prescribed to treat the underlying cause of the irregular heartbeat.

Living and Management

Living and management of your dog’s irregular heartbeat involves follow-up appointments scheduled by your veterinarian only if necessary for specific diseases. If your dog experiences occasional heart rhythm irregularities without compromising health, no further treatment beyond routine health check-ups will be required.

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