A heartbeat is irregular when it is too fast, too slow or has an erratic pattern. Not all irregular heartbeats are serious — indeed, a slow heartbeat in an athletic dog could just be proof he is very fit!
However, if you suspect your dog has an irregular heartbeat and especially if he shows symptoms, for peace of mind, get him checked by your veterinarian.
Heart rhythm and rate are controlled by electrical impulses that tell the heart muscle when to contract and relax. In turn, these impulses are influenced by the nervous system, blood electrolyte, and drugs, as well as the health of the heart itself.
Symptoms of Arrhythmia in Dogs
The most common symptoms of a significant arrhythmia (irregular heartbeat) are heavy or rapid breathing, not wanting to exercise and fainting episodes.
Rapid, shallow breathing can be a sign of heart disease (among other things) while skipped heartbeats can lead to loss of blood pressure and fainting. If you notice any of these symptoms, please take your dog to the vet for a checkup.
Most times, your pet will give you clues that something is wrong, but unfortunately the distressing worst-case scenario of sudden death can happen without warning.
Signs to be alert for:
- Lack of energy
- Rapid, shallow breathing
Nick Shroeder, DVM, DACVIM, discusses several common arrhythmias in dogs — including atrial fibrillation, premature beats, atrioventricular block, supraventricular tachycardia and ventricular tachycardia — in his article Common Arrhythmias in Dogs and Cats.
What Causes an Irregular Heartbeat?
Causes can be divided into 2 broad groups:
- Non-cardiac related
Heart rate is influenced by diseases distant from the heart — for example, underactive thyroid glands, Addison’s disease and kidney disease. In simple terms, these conditions cause electrolyte imbalances, and electrolytes such as sodium and potassium regulate nerve function and muscular contraction in organs such as the heart.
An important cause of an irregular heartbeat is heart disease. If the heart becomes enlarged, or the muscle thickened, it takes nerve impulses longer to reach their target cells. This means electrical messages get out of sync with one another, and skipped beats can result. This happens with conditions such as dilated cardiomyopathy (DCM; a large, flabby heart) and hypertrophic cardiomyopathy (HCM; the heart muscle becomes too thick).
Sadly, another cause can be a tumor at the heart base that interferes with nerve conduction.
Your veterinarian can learn a lot by listening to your dog’s heart with a stethoscope. This tells her about heart rate, murmurs and lung health. From there, she may recommend an electrocardiogram (EKG )and blood work. If the dog has an intermittent problem, he can be fitted with a special harness that monitors his heartbeat over 24 hours.
An EKG is a wonderful tool for showing where the problem lies. The pattern of muscular contraction in the heart is replicated on the EKG feed and can tell us which heart chambers are enlarged, and whether a signal generator within the heart is faulty.
Screening blood tests give clues as to illnesses that may affect heart rhythm and rate.
Treatment for a Dog With an Irregular Heartbeat
If an underlying problem such as an underactive thyroid is diagnosed, the best therapy is to treat this disease — then the arrhythmia should correct itself.
If the heart itself is the problem, your veterinarian will prescribe medications to regulate the heartbeat in your dog, such as beta blockers, digitalis or modern drugs such as pimobendin. If your pet is having trouble breathing, he may need hospitalization for oxygen therapy and strict rest.
Weight control plays an important role because carrying extra weight puts a strain on the circulatory system. Many other factors are outside your control, but be vigilant for signs of breathing difficulties and lethargy, because early diagnosis can make all the difference.
- Cardiovascular Disease in Small Animal Medicine. Wendy Ware. Publ: Manson Publishing.
- Cardiorespiratory Diseases of the Dog and Cat. Martin & Corcoran. Publ: Blackwell Science.
This pet health content was written by a veterinarian.