Meet Snuffy. He’s a 6-year-old Havanese/Tibetan Terrier. Snuffy’s owner, Eleanor, rescued him when he was 7 months old. He spent the first few years of his life being somewhat of a mystery, as he was often lethargic and none of his veterinarians could find the reason why.
When he was about 3 years old, Snuffy’s heart rate dropped to below 60 beats per minute. (Healthy young dogs in the hospital have heart rates typically over 100 beats per minute.) Eleanor rushed him to the SAGE Emergency Room where he was treated and referred to SAGE Cardiologist Dr. Andrew Waxman. After observing Snuffy and running several tests, Dr. Waxman diagnosed the pup with Sick Sinus Syndrome (SSS), a rare heart rhythm disorder. Finally, Eleanor had answers.
The sinus node of the heart
The sinus node is a group of cells in the right atrium that creates the signals that regulate the heartbeat, depending on the dog’s activity. When a healthy dog runs and plays, the sinus node sends signals to speed up the heart beat; when the dog is at rest, the signals decrease. Dogs with SSS have an irregular series of signals that are too slow for their activity level, resulting in lethargy, activity intolerance, and fainting.
Here is a video of Snuffy at his lowest:
A puzzling illness
Symptoms like lethargy and fainting can point to other illnesses, which is part of what makes diagnosing sick sinus syndrome so difficult. In many dogs with SSS the heart rate can be normal during the examination. In confusing cases dogs may be fitted with a heart monitor (Holter monitor) to help find abnormal heart rates or rhythms. Snuffy’s heart monitor showed abnormally slow heart rates with rates being as low as 20 beats per minute. Snuffy’s age was another red herring: most cases of sick sinus syndrome are found in senior dogs, and rarely in young dogs like Snuffy.
Dr. Waxman implanted a pacemaker in Snuffy and his life started to improve. He had more energy and wanted to play and socialize. Eleanor was also able to take him to the dog park again.
Here is a video of Snuffy after Dr. Waxman implanted his pacemaker.
Snuffy recently returned to Dr. Waxman when his pacemaker battery needed to be changed. Pacemaker batteries usually last a few to several years. While older animals rarely require battery changes, younger dogs may require 1-2 in their lifetime. Snuffy is now on his second pacemaker.
“With successful pacemaker implantation, most dogs regain a normal quality of life with few lifestyle adjustments for pacemaker care,” Dr. Waxman says. “In most cases the lifespan is unaffected by this condition once the pacemaker is placed.”