Irregular Heartbeat in Dogs

An irregular heartbeat is not uncommon in dogs and may not be a serious health problem, but should be checked out by your veterinarian. Dogs hearts are similar to humans in that their heartbeat increases with exertion and decreases during rest. What you feel is a rapid heart rate in your dog may actually be a normal heart rate because their heart beats much faster than your own. It may be hard to detect in your dog and is most often found during a routine examination. If you suspect your dog has an irregular heartbeat, you should take him to your veterinarian right away, as this can be a sign of a serious disorder. Sometimes, an owner doesn't recognise this issue is present and it is diagnosed on a routine health check.

Irregular heartbeat, or arrhythmia, is an abnormal electrical activity pattern in the muscle of the heart. Any type of disturbance or variance of a normal heart rate or rhythm in dogs is considered canine arrhythmia.

• Fast heartbeat
• Slow heartbeat
• Fainting
• Breathing trouble
• Coughing
• Fatigue
• Dizziness
• Weakness
• Decreased ability to exercise

 Types

• Sinus arrhythmia
• Atrial fibrillation
• Atrioventricular block
• Ventricular tachycardia
• Premature beats

Although any age, sex, and breed of dog can have an irregular heartbeat, some breeds are more susceptible to certain types of arrhythmia. In a number of cases, an irregular heartbeat is caused by a hidden disorder like abnormal electrolytes, systemic disease, heart disease, injuries, or infection.  

• Sinus arrhythmia – Short-muzzled dogs, such as Bulldogs, Pug, and Pekingese are more commonly affected due to their difficulty breathing
• Atrial fibrillation – Giant breed dogs, like Saint Bernards, Great Danes, and Mastiffs are more susceptible to this type of arrhythmia
• Atrioventricular block – Can sometimes be caused by a congenital disorder or an underlying disorder
• Ventricular tachycardia – More common in Boxers and Doberman Pinschers
• Premature beats – Heart disease, abnormal electrolytes, and systemic disorders can cause premature beats

Your veterinarian will do a complete physical examination, listen to your dog’s heart, and check other vitals. It is important to give the veterinarian as much information as you have about what brought you to the clinic, when the symptoms started, and how often you have witnessed these symptoms. He will also need to know if the problem has been getting worse.

 Several lab tests will need to be run to determine the amounts of potassium, urea, sodium, magnesium, phosphorus, chloride, creatinine, and calcium in your dog's bloodstream. The veterinarian technician will take a blood and urine sample to check:

• CBC
• Blood chemistry panel
• Blood gases
• Urinalysis
• Electrolytes

 The veterinarian will also do some other tests that are necessary to diagnose your dog’s irregular heartbeat, such as:

• Chest radiographs will be taken to look for abnormalities
• An ECG (electrocardiogram) can show any abnormal premature contractions or accelerated/decelerated heart rate
• Echocardiogram
• Atropine response test to find the true cause of the irregular heartbeat

 Your dog’s veterinarian may not be able to get conclusive results if the heartbeat irregularity is not present at the time of your visit. If this happens, he will send your dog home with a Holter monitor to obtain a record of your dog’s heartbeat for 24 hours. A Holter monitor is a portable ECG machine that is attached to electrodes and wrapped with a bandage to continuously read your dog’s heartbeat. The veterinarian or a cardiology technician will review the results the next day to check the results and decide on the best treatment plan.

Your veterinarian may decide to hospitalize your dog in the case of acute respiratory distress. Oxygen and IV fluids will be given to help stabilize his breathing. Additionally, medications will be given in the case of any of these chronic conditions:

• Sinus arrhythmia is usually treated with medication such as Atropine or Mexiletine
• Atrial fibrillation is regulated by Digoxin and possibly extended-release Diltiazem
• Atrioventricular block can be treated by Theophylline or Propantheline. The veterinarian may decide a pacemaker should be surgically placed if necessary. If the irregular heartbeat is caused by an underlying disorder, treatment will be given accordingly
• Ventricular tachycardia may be treated with antiarrhythmic therapy in breeds predisposed to this condition. Lidocaine, Sotalol and Mexiletine are sometimes given if your dog is in acute VT
• Premature beat is medicated with Mexiletine or Sotalol

Your dog’s prognosis depends on the reason for the irregular heartbeat. If your dog’s irregular heartbeat is not considered a threat to his health and is asymptomatic, the veterinarian will just have you bring him back for regular check-ups.

In the case of any of the above ailments, the prognosis is good as long as it is caught and treated early enough. Medication and frequent check-ups with your veterinarian will be be continued indefinitely.