Heartbeat arrhythmia, also known as cardiac dysrhythmia or irregular heartbeat, is a condition that describes abnormal electrical heart activity. The heartbeat may be too slow, too fast, too weak, too strong, regular, or irregular. Some dogs live with a mildly irregular heartbeat with no negative side effects, while others suffer from associated effects. Severe arrhythmia can result in death.

Irregular heartbeat is fairly common in dogs, and in most cases, is not a cause for concern. A case of arrhythmia should be investigated, however, because it may be a precursor of a serious underlying condition.
Sinus arrhythmia occurs when the dog’s heart rate accelerates during inhalation and slows during exhalation.

Heartbeat arrhythmia may be caused by genetic factors, infections, breed predisposition, congenital heart abnormalities, gastrointestinal disease, brachycephalic conformation, digoxin therapy, heart disease, toxins, dehydration or electrolyte imbalance, blood loss, stress, and injury. Sinus arrhythmia is caused by changes in vagal tone or anything that asserts pressure on the vagus nerve.

There is no way to prevent irregularities in heartbeat, mostly because there are so many potential causes. Keeping your dog away from avoidable stresses and toxins will help, as does making sure it has a good diet and access to fresh, clean drinking water. Regular checkups will turn up any problems as soon as possible so that they can be treated accordingly.

The symptoms of arrhythmia are few: a noticeably irregular heartbeat – it may be too slow, too fast, or too weak. It may skip a beat. You may notice that it speeds up and slows down according to your dog’s breath. The dog may lose consciousness or become weak. Any irregularity in a dog’s heartbeat should be seen to by a vet as soon as possible.

Dogs at Risk
Some breeds are more likely to develop irregular heartbeats, like those which fall into the brachycephalic group: Lhasa Apsos, Pekinese, Shar-Peis, Bulldogs, Boxers, Shih Tzus, and Pugs. Arrhythmia may affect any dog, of any age, and in either gender. Mixed-breed dogs may also develop this disorder.

Testing and Diagnosis
When arrhythmia is first noticed, the vet will do a complete exam and history on the dog. He or she will ask about onset of any unusual behaviours, activities, symptoms, and possible incidents that may be connected to the irregular heartbeat.
The vet will perform a variety of tests to look at the dog’s heart; possible tests may include an electrocardiogram to show abnormal cardiac electrical conduction; x-rays of the head and neck to check for abnormal structure that may cause airway problems; or a pharyngoscopy or laryngoscopy to visually examine the respiratory tract.

Treatment and Prognosis
The treatment plan will depend upon the severity of the irregularity as well as the underlying cause. Many dogs can enjoy long, full lives with cardiac arrhythmia, while others have severe episodes that are life-threatening. Advanced heart disease, which can cause arrhythmia, carries with it a grave prognosis.