Cardiac Conditions That May Warrant A Pacemaker In Dogs

If a dog has an arrhythmia (abnormal heart rhythm) or a bradyarrhythmia (heart rate that is too slow to support the dog’s daily activities), s/he might benefit from a pacemaker. An artificial pacemaker is an electronic device that maintains the heart rate, and therefore circulation, by stimulating the heart to contract when the heart’s own electrical activity fails to do so.

Symptoms Of A Slow, Irregular Heart Rate

If your pet suffers from a bradycardia disease, s/he will likely exhibit one or more of these clinical signs:

• Lethargy
• Weakness
• Fainting
• Collapse
• Decreased appetite
• Sustained increased resting respiratory rate/effort

Please schedule an appointment with your family veterinarian at your earliest convenience if you notice any of these signs. Both primary veterinarians and cardiologists can diagnose bradyarrhythmias through electrocardiogram.

Diagnosis

Though any veterinarian can diagnose a pet with a heart condition, it’s best if a board-certified cardiologist evaluates the patient for diseases that can be treated with a pacemaker. There are three common heart diseases that warrant the implantation of a pacemaker:

• Sick Sinus Syndrome (SSS): A condition in which the portion of the heart that generates an electrical impulse, the sinoatrial node, does not work appropriately, resulting in irregular fast and slow heart rhythms and corresponding clinical signs mentioned above
• Atrial Standstill: A rare heart rhythm disturbance characterized by the absence of electrical and mechanical activity in the atria (top portion of the heart), resulting in the development of an escape rhythm from the atrioventricular junction or subsidiary ventricular pacemaker cells
• Advanced Atrioventricular (AV) Block: A condition in which the impulse generated in the sinoatrial (SA) node in the atrium does not propagate through the AV node to the ventricles. Because the impulse is blocked, an accessory pacemaker in the ventricles will typically activate the ventricles. This is known as an escape rhythm, and keeps these patients alive

To assess whether a dog can receive a pacemaker, a cardiologist performs a comprehensive examination, which may or may not include:

• Complete blood work
• Urinalysis
• Thoracic radiographs
• Abdominal radiographs (+/- abdominal ultrasound)
• Echocardiogram, also known as a heart ultrasound, to assess for cardiac structural disease
• 6-lead electrocardiogram
• Tick serology
• Blood pressure evaluation, prior to implantation, to rule out extra-cardiac causes of the clinical signs and assess if the patient is a good pacemaker candidate

Pacemaker Implantation

If a patient has a bradyarrhythmia, a cardiologist may recommend permanently implanting a pacemaker. A pacemaker will help prevent congestive heart failure, sudden death, previously mentioned clinical signs, and/or other long-term health conditions. The ideal patient has little to no structural cardiac disease. Patients who have an underlying structural cardiac disease may not be good candidates due to a potentially poor long-term prognosis.

Most dogs (weighing more than 3 kilograms) are able to undergo a procedure known as transvenous pacemaker implantation. In this procedure, the surgeon places the generator (battery) under the muscle in the side of the neck. The lead extends through a jugular vein all the way into the right side of the heart. The tip is then secured in the right ventricular muscle. Once secured, the pacemaker contacts the inside of the heart muscle to deliver pulses of electricity that stimulate the heart muscle to contract. Each generator is programmed specifically for your pet. This procedure does require the patient to be under general anesthesia.

Alternatively, cardiologists implant a pacemaker in cats and dogs that weigh less than 3 kilograms using a different method. Typically, in these cases, the generator must be placed within the abdomen, and the lead is surgically attached to the outer surface of the heart (epicardial placement) through an incision in the diaphragm. A veterinary surgeon usually inserts these pacemakers with the assistance of the veterinary cardiologist.
Once the pacemaker has been successfully implanted, the prognosis is generally good. In fact, many patients live for years with implanted pacemakers.

Recovery

After the procedure, your pet is often able to return home within two days with a large bandage around his or her neck. The bandage protects the operation sites from being irritated, helps to reduce any swelling, prevents infection, and restricts head movement (minimizing the risk of lead dislodgement). Your pet may be sent home with antibiotics and/or pain medications. Once home, activity should be restricted for four to five weeks to allow proper healing. It is imperative that you prevent your pet from activities that over-stretch the neck such as jumping up or rough housing with other pets.

Because of the position of the pacemaker and lead, your pet should never be restrained by a neck collar. It is preferable to use a harness to restrain your pet in the future.

Your pet should also never have blood drawn from the jugular vein again in order to prevent damage to the device.

We strongly encourage periodic follow-up examinations (at least every six months unless clinical signs warrant immediate evaluation). During the follow-up examinations, the cardiologist assesses the pacemakers using a temporary placement of an external magnet and a computer. Patients do not need to have sedation or anesthesia for this assessment. If needed, we can adjust the pacemaker during the appointment to maximize battery life and function. These follow-ups must only be performed by a veterinary cardiologist.

CARE

At CARE, we have the veterinary specialists, staff and advanced technology necessary to diagnose and perform permanent and/or temporary pacemaker implantations. Further, we will work with your family veterinarian to determine the best course of treatment for your beloved pet. If your dog or cat has been diagnosed with a heart disease that warrants a pacemaker, ask for a referral to our Cardiology department.