Common Heart Diseases in Dogs that May Require a Pacemaker

Pacemakers can be implanted in dogs diagnosed with arrhythmia (abnormal heart rhythm) or bradycardia (bradyarrhythmia) which is an abnormal heart rhythm that is characterized by a very slow heart rate. Artificial pacemakers can also be used when a dog’s heart stops beating for prolonged periods, which can be life-threatening.

Pacemaker implantation is generally required in the following heart diseases:

Sick Sinus Syndrome (SSS)

When the sino-atrial node (a part of the heart that generates an electrical impulse to stimulate heart contraction) does not work properly, the beating of the heart will become irregular.

Atrial Standstill

A condition that is characterized by the absence of electrical and mechanical activity in the upper chambers of the heart (atria).

Advanced Atrioventricular (AV) Block

The problem occurs when the electrical impulse generated by the SA node in the atrium does not reach the AV node to the ventricles. As a result, an accessory pacemaker located in the ventricle is activated.

Dogs with these conditions tend to show the following symptoms:

• Weakness
• Lethargy
• Fainting
• Decreased appetite
• Increase in respiratory rate
• Difficulty breathing
• Exercise intolerance

How do pacemakers work?

A pacemaker has two parts:

• A generator which is composed of the generator switch, lithium battery, and computer chip
• Leads - these are wires that are attached to the muscles inside the heart. The wires extend from the generator through the neck veins.

A pacemaker can be programmed to ensure that the dog’s heart rate does not fall below the acceptable range set by a veterinarian, which is generally between 80 - 120 beats per minute. When the dog’s heart rate slows down, the pacemaker is activated to stimulate heart contractions until the rhythm of the heart is reset and it can continue beating on its own.

The implantation of a pacemaker is performed while a dog is under anesthesia. It’s a minimally invasive procedure that involves making a small incision in the neck of the dog where the leads are inserted in the external jugular vein. The pacemaker is tucked under the skin of the dog’s neck before the incision is closed with stitches. The batteries are generally long-lived but when they wear out, a replacement can be done quite easily.

During the insertion and manipulation of the leads through the jugular vein to the heart, a veterinarian will depend on fluoroscopy for visualization. This can help ensure that the leads are attached to the right place. Fluoroscopy is a real-time x-ray that is the same procedure used during catheterization of the heart.

In some cases, the pacemaker may be placed within the abdomen and the lead attached to the heart’s outer surface through an incision in the diaphragm. This approach is generally indicated if a dog has a skin infection or for a very small dog (weighing less than 6 pounds) in which insertion of a pacemaker in the neck is difficult or not possible.

Potential Risks of Pacemaker Placement in Dogs

Like any other surgical or medical procedure, pacemaker implantation is not without risks. It’s important for dog owners to understand these potential complications.

Complications associated with general anesthesia

The implantation of a pacemaker is performed while the dog is under general anesthesia. The risks associated with general anesthesia include drug reactions, irritation of the airways, and rarely, death. A significant drop in the dog’s heart rate is a common observation. The anesthetic drugs may also cause the dog’s heart to stop completely.

Fortunately, anesthetic risks can be reduced with an experienced anesthetist, close monitoring, and state-of-the-art surgical equipment. Some procedures can be undertaken before anesthetic drugs are administered to temporarily pace the heart if ever the need arises. These include placing a temporary lead in the dog’s heart via one of the veins in the legs or by trans-thoracic pacing.

Bleeding

This may range from mild bleeding that does not require treatment, to moderate bleeding that requires a blood transfusion. Death can occur as a result of severe bleeding.

Worsening of the arrhythmia

The problem can occur while the pacemaker is still being attached. While medications can correct most arrhythmias, death may result from severe arrhythmia or the dog may not respond positively to medications.

Post-operative complications

Complications during the post-operative recovery period may include infection in the incision, the opening of the incision (wound dehiscence), or the formation of a fluid-filled pocket known as a seroma. There may also be mild complications experienced by the dog, such as some discomfort and/or bruising.

Lead dislodgement

This is a serious complication that can happen when the pacemaker malfunctions. Dislodgement of the lead usually occurs during the first month after the procedure because there is not enough time for scar tissue to form around the lead and keep it in place. However, lead dislodgement can occur at any time - months or years - after the procedure.

Infections

This is considered one of the most serious complications after pacemaker implantation. An infection in any part of the dog’s body can reach the pacemaker implant and get into the heart via blood circulation. Infections affecting the pacemaker implant tend to be generally serious and have high risks for fatal complications. Immediate medical intervention is required. There may be a need for another surgery for pacemaker implant replacement.

Blood clots

The formation of blood clots after pacemaker implantation in dogs is very rare. The blood clots can block blood vessels or travel to the lungs via the blood circulation resulting in mild to severe respiratory difficulties.

Pacemaker Alternatives for Dogs

Alternative management of dogs with bradycardia or arrhythmia is medical management that includes oral medications. Unfortunately, many dogs don’t respond well to medical management and those that do may only respond positively for a short time before symptoms return. As the symptoms worsen, congestive heart failure eventually develops. At this stage, medical management is unable to control symptoms or slow down progressive heart disease.

Follow-Up Care After Pacemaker Implantation in Dogs

• After surgery to implant the pacemaker, proper wound care and close monitoring of the two small incisions on the dog’s neck should be made twice daily. Any sign of infection should be brought to the attention of your vet immediately.
  
• A dog with a pacemaker implant can no longer wear collars and neck leads because they may damage the pacemaker or cause it to get dislodged. Instead, a chest harness should be worn. A harness keeps pressure off the dog’s neck where the pacemaker’s generator is located. Make sure that all veterinarians, groomers, dog trainers, etc. are made aware of the dog’s pacemaker.

• During the first month after the procedure, strict cage rest is required to prevent dislodgement of the lead and reduce the possibility of complications affecting the incisions.
  
• The first checkup will likely be a month after the procedure. Depending on the dog’s healing progress, the vet may require your dog to be checked every six months. If there is a need to adjust the settings of the pacemaker, a vet can perform the reprogramming.
  
• Your dog can gradually resume normal activities after a month of restricted activity after surgery.

Read more:

Why does my pet need an echocardiogram?

Why does my pet need an electrocardiogram (ECG)?

Why does my pet need x-rays?

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