Abnormal heart rhythms, also known as cardiac arrhythmias, are a common problem in dogs. These irregular heartbeats can range from mild and harmless to serious and potentially life-threatening.
It is important for pet owners to be aware of the signs and causes of abnormal heart rhythms in dogs, as well as the treatment options available.
The Heart of the Matter
The heart is a muscular organ that pumps blood throughout the body. It has four chambers: the left and right atria, and the left and right ventricles.
The right atrium receives oxygen-depleted blood from the body and pumps it into the right ventricle, which then pumps the blood into the lungs.
The left atrium receives oxygen-rich blood from the lungs and pumps it into the left ventricle, which pumps the oxygen-rich blood out to the rest of the body.
The Heart’s Electrical Conduction System
The heart has its own electrical conduction system, which coordinates the contractions of the heart muscle and ensures that blood is pumped efficiently. The sinoatrial node, located in the right atrium, serves as the heart’s natural pacemaker and generates electrical impulses that stimulate the heart to contract.
When the electrical signals from the sinus node reach the AV node, they are delayed for a fraction of a second before being transmitted to the ventricles. This delay allows the atria to contract and pump blood into the ventricles before the ventricles contract and pump blood out to the rest of the body.
The heart’s blood-pumping action is driven by the relaxation and contraction of the heart muscle, which is controlled by the autonomic nervous system.
The sympathetic nervous system speeds up the heart rate, while the parasympathetic nervous system slows it down.
Dog Breeds at Risk of Developing Abnormal Heart Rhythms
Certain breeds of dogs may be at increased risk of developing abnormal heart rhythms, or arrhythmias. Some examples of breeds that may be predisposed to arrhythmias include:
Doberman Pinschers
Doberman Pinschers are prone to a variety of heart problems, including atrial fibrillation (AF), supraventricular tachycardia (SVT), and ventricular tachycardia (VT).
Boxers
Boxers are prone to a variety of heart problems, including atrial fibrillation, supraventricular tachycardia, and ventricular tachycardia.
Boxer cardiomyopathy is a type of heart disease that is common in boxers. It is a form of dilated cardiomyopathy, a condition in which the heart becomes enlarged and weakened, making it unable to pump blood effectively.
Boxer cardiomyopathy is often inherited and can occur in dogs as young as one year old. Symptoms of the condition may include coughing, difficulty breathing, fatigue, and loss of appetite. In severe cases, it can lead to congestive heart failure and sudden death.
Greyhounds
Greyhounds are prone to a variety of heart problems, including AF, SVT, and VT.
Cocker Spaniels
Cocker Spaniels are prone to a variety of heart problems, including AF, SVT, and VT.
German Shepherds
German Shepherds are prone to a variety of heart problems, including AF, SVT, and VT.
Miniature Schnauzers
Miniature Schnauzers are prone to a variety of heart problems, including AF, SVT, and VT.
All Breeds at Risk
It is important to note that any dog, regardless of breed, can develop an abnormal heart rhythm.
Common Arrhythmias in Dogs
There are several types of arrhythmias that can affect dogs, including the following:
Supraventricular Tachycardia (SVT)
Supraventricular tachycardia (SVT) is a type of rapid heart rhythm that originates from the upper chambers of the heart (the atria) in dogs. It is characterised by an abnormally fast heart rate that can range from 220 to 280 beats per minute.
SVT is a serious condition that can cause symptoms such as difficulty breathing, weakness, collapse, and even death if left untreated.
Atrial Fibrillation
Atrial fibrillation (AF) is a type of abnormal heart rhythm that affects the upper chambers of the heart (the atria) in dogs. It causes rapid and irregular contractions of the atria, which can lead to a fast, irregular heart rate.
AF is most commonly seen in older dogs and is often associated with underlying heart disease, such as mitral valve disease or dilated cardiomyopathy.
In some cases, surgery may be necessary to correct the underlying problem.
Ventricular Tachycardia
Ventricular tachycardia is characterised by a rapid heartbeat that originates in the upper chambers of the heart, known as the atria. It occurs when the ventricles beat too quickly and can be life-threatening if left untreated.
Sinus Bradycardia
Sinus bradycardia is a type of slow heart rate that occurs when the sinus node, the heart’s natural pacemaker, generates electrical impulses at a slower-than-normal rate.
It can be caused by various factors, including certain medications, electrolyte imbalances, and underlying health conditions such as heart disease or hypothyroidism.
Symptoms of sinus bradycardia in dogs may include weakness, lethargy, exercise intolerance, and fainting. In severe cases, sinus bradycardia can lead to life-threatening complications, such as cardiac arrest.
Sick Sinus Syndrome in Dogs
Sick sinus syndrome is a condition that affects the sinus node, the part of the heart responsible for generating electrical impulses.
In dogs, sick sinus syndrome can cause a variety of symptoms, including weakness, fatigue, collapse, and fainting. It can also lead to other serious complications, such as heart failure and arrhythmias.
The exact cause of sick sinus syndrome in dogs is not well understood, but it is thought to be related to damage or abnormalities in the sinus node or the surrounding tissues. Some dogs may be predisposed to the condition due to underlying health issues, such as high blood pressure or heart disease.
The diagnosis of sick sinus syndrome in dogs typically involves a physical examination, blood tests, electrocardiography (ECG), and other diagnostic tests.
Treatment may involve medications to regulate the heart rate and blood pressure, as well as surgery to repair or replace damaged tissue. In some cases, a pacemaker may be recommended to help regulate the heart’s electrical activity.
Common Causes of Abnormal Heart Rhythms in Dogs
There are several potential causes of arrhythmias (abnormal heart rhythms) in dogs. Some common causes and risk factors include:
1. Underlying heart disease
Dogs with underlying heart disease, such as valvular heart disease or dilated cardiomyopathy, may be more prone to developing arrhythmias. However, as you’ll see below, there are many non-cardiac causes of arrhythmias in dogs.
2. High Blood Pressure
High blood pressure, or hypertension, can cause strain on the heart and increase the risk of arrhythmias.
3. Thyroid Problems
Abnormalities in thyroid function, such as hyperthyroidism or hypothyroidism, can affect the heart and increase the risk of arrhythmias.
4. Medications
Some medications, such as certain types of diuretics, beta blockers, and calcium channel blockers, can affect the heart and increase the risk of arrhythmias.
5. Electrolyte Imbalances
Abnormalities in electrolyte levels, such as low potassium or high calcium, can affect the heart and increase the risk of arrhythmias.
6. Age
Older dogs are more prone to developing arrhythmias due to the natural aging process and the increased risk of underlying health conditions.
Signs of Abnormal Heart Rhythms in Dogs
There are several signs that may indicate an abnormal heart rhythm, or arrhythmia, in dogs. Some common signs to look for include:
1. Rapid or irregular heartbeat
A rapid or irregular heartbeat may be a sign of an arrhythmia.
2. Weakness or lethargy
Dogs with arrhythmias may experience weakness or lethargy due to decreased oxygen and nutrient delivery to the body’s tissues.
3. Difficulty breathing
Dogs with arrhythmias may have difficulty breathing due to decreased oxygen delivery to the body.
4. Collapse
In severe cases, dogs with arrhythmias may collapse due to the effects of the abnormal heart rhythm on the body.
5. Chest pain
Some dogs with arrhythmias may experience chest pain due to the strain on the heart. Pain can be difficult to assess in dogs because they’re so good at hiding it.
If your dog is in pain, he or she may withdraw from you, not want to eat, exercise, or may even whine or vocalize.
Diagnosing Abnormal Heart Rhythms in Dogs
If your veterinarian suspects your dog has a cardiac arrhythmia or abnormal heart rhythm, there are a few tests they will perform. These include:
- Blood work
- Complete blood count
- Biochemical profile
- EKG can be used to diagnose cardiac arrhythmias
- Chest x-ray can help determine if heart disease or heart failure is present
- Ultrasound of the heart (known as the gold standard)
Holter monitoring
A portable device called a Holter monitor is used to track the electrical activity of the heart over time.
Due to its prolonged recording time, it can be used to monitor sporadic or transient cardiac arrhythmias that may be challenging to spot during a routine clinical examination.
Holter monitors are frequently used to identify particular types of heart disease and abnormal heart rhythms in Boxer dogs and Doberman Pinschers.
Treating Abnormal Heart Rhythms in Dogs
Treatment of abnormal heart rhythms in dogs may involve medications to control the heart rate or rhythm, lifestyle changes, or surgery.
Ultimately, treatment for an irregular heart rhythm depends on the underlying cause.
In some cases, surgical procedures, including the implantation of a pacemaker, may be necessary to correct the arrhythmia.
Implantation of a Pacemaker
Pacemakers are medical devices that are used to treat arrhythmias (abnormal heart rhythms) in dogs. The procedure to implant a pacemaker in a dog is similar to the procedure in humans. It is typically performed by a board-certified veterinary cardiologist and requires general anesthesia.
Here is a general overview of the procedure:
Pre-surgical Preparation
The dog will undergo a physical examination and diagnostic testing to determine if a pacemaker is necessary and to ensure that the dog is healthy enough for the procedure.
Anesthesia
The dog will be given general anesthesia to ensure that they are comfortable and pain-free during the procedure.
Surgical Preparation
The area where the pacemaker will be implanted will be shaved and sterilized. The dog will be positioned on the operating table.
Pacemaker Implantation
The pacemaker consists of two main components: the pulse generator and the leads. The pulse generator is a small box that contains a battery and electronic circuits.
The leads are thin wires that are attached to the pulse generator and are inserted into the heart through a small incision in the chest. The leads are then guided through a vein until they reach the heart. Once they’re in place, they are attached to the pulse generator and the devise is tested to make sure it’s workig properly.
Closing the Incision
The incision is closed with sutures or surgical staples.
Recovery
The dog will be monitored closely during recovery to ensure that the pacemaker is working properly and to check for any complications.
The specific details of the procedure may vary depending on the specific needs of the dog and the preferences of the surgeon. If your dog requires a pacemaker, it is important to speak with a veterinarian and a board-certified veterinary cardiologist to determine the best course of treatment.
Catheter Ablation
Catheter ablation involves the use of a catheter, which is a thin, flexible tube, to deliver energy to specific areas of the heart. It works by destroying or modifying the abnormal tissue responsible for the arrhythmia.
This procedure is typically performed by a cardiologist or electrophysiologist, and it is done under general anesthesia.
Catheter ablation can be used in combination with other treatments (including surgery and medications) to manage arrhythmias.
The success rate of catheter ablation in dogs varies depending on the type and severity of the arrhythmia, as well as the overall health of the dog.
Your veterinarian or a specialist will be able to provide more information on the potential benefits and risks of this procedure for your dog.
Medications for Arrhythmias in Dogs
There are several medications that may be used to treat arrhythmias (abnormal heart rhythms) in dogs.
The specific medication and dosage will depend on the type and severity of the arrhythmia, as well as the overall health and age of the dog. Some common medications used to treat arrhythmias in dogs include:
Beta blockers
These medications work by blocking the effects of certain hormones that can increase the heart rate. They are often used to treat supraventricular tachycardias (rapid heart rhythms that originate from the atria) and atrial fibrillation (irregular contractions of the atria).
Calcium channel blockers
These medications work by relaxing the muscles of the heart and blood vessels, which can help to reduce the heart rate and improve blood flow. They are often used to treat supraventricular tachycardias and atrial fibrillation.
Antiarrhythmic medications
These medications work by altering the electrical activity of the heart and can help to restore a normal heart rhythm.
They are often used to treat a variety of arrhythmias, including supraventricular tachycardias, atrial fibrillation, and ventricular tachycardias (rapid heart rhythms that originate from the ventricles).
Digoxin
This medication works by strengthening the contractions of the heart and can be used to treat certain types of arrhythmias, including atrial fibrillation and atrial flutter (rapid, irregular contractions of the atria).
Can You Prevent Abnormal Heart Rhythms in Dogs?
Preventing abnormal heart rhythms in dogs may involve maintaining a healthy weight, providing regular exercise, and avoiding certain medications or foods that may trigger arrhythmias.
It is also important to have your dog regularly screened for heartworm infection and to keep up with their heartworm prevention medication.
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CONCLUSION
Abnormal heart rhythms are a common problem in dogs that can range from mild to serious.
It is important for pet owners to be aware of the signs and causes of arrhythmias, as well as the treatment options available. By working closely with a veterinarian and following their recommendations, it is possible to manage and treat abnormal heart rhythms in dogs and help ensure a long and healthy life.
Works Cited
“Arrhythmias (Abnormal Rhythms) in Dogs.” Cornell University College of Veterinary Medicine, 13 Dec. 2017, www.vet.cornell.edu/hospitals/companion-animal-hospital/cardiology/arrhythmias-abnormal-rhythms-dogs.
Becker, Dr. Marty. “How to Check Your Dog’s Vital Signs at Home – Vetstreet.” Vetstreet, 21 Sept. 2022, www.vetstreet.com/dr-marty-becker/check-your-dogs-vital-signs-at-home.
“What Is Normal Dog Temperature, Heart Rate and Respiration?” What Is Normal Dog Temperature, Heart Rate and Respiration?, 19 Jan. 2018, www.dixieanimalhospital.com/blog/13048-what-is-normal-dog-temperature-heart-rate-and-respiration.
“Holter Monitor in Dogs | VCA Animal Hospital.” Vca, vcahospitals.com/know-your-pet/holter-monitor-in-dogs. Accessed 12 Dec. 2022.
“Pacemaker Fact Sheet | Davies Veterinary Specialists.” Davies Veterinary Specialists, vetspecialists.co.uk/fact-sheets-post/pacemaker-fact-sheet. Accessed 12 Dec. 2022.
“Cardiac Arrhythmias in Dogs and Cats.” VetSpecialists.com, 7 Apr. 2020, www.vetspecialists.com/vet-blog-landing/animal-health-articles/2020/04/07/cardiac-arrhythmias-in-dogs-and-cats.