Mending the Hearts of a Beloved Dog Breed

Suzanne Cunningham, a veterinary cardiologist and associate professor at the Cummings School of Veterinary Medicine, loves boxer dogs, but they’ve broken her heart since she was a child.

As a breed, Boxers are prone to a type of heart disease called arrhythmogenic right ventricular cardiomyopathy (ARVC), which can also occur in humans. It is a disease of the small connections between heart muscle cells called desmosomes. The desmosomes weaken and the heart cells pull apart, leaving scar tissue behind. The disease can go undetected in humans and dogs with no symptoms, causing abnormal heart rhythms, enlargement of the heart, and even death.

“This illness is so frustrating because sometimes the first clinical sign is sudden death,” said veterinarian Luis Dos Santos, a resident cardiologist who works at Cunningham. “The pet owner may not even know their dog had potentially fatal heart disease.”

Cunningham was nine years old when she suddenly lost her first boxer to heart disease. She lost another beloved boxer, Tyler (pictured above), to ARVC a few years ago. The desire to prevent such a loss from happening to others inspired her to research ARVC.

“Tyler was the most amazing animal I have ever known. I know what people are going through and it just tears you up, ”said Cunningham. “Anything we can do to improve the detection or treatment of the disease is really what we are looking for.”

Standard screening for ARVC in boxers involves a combination of a family history, data collected from a portable 24-hour cardiac monitor, and an ultrasound of the heart called an echocardiogram. Most of the time, ARVC is not recognized until a boxer is 5 or 6 years old, after many dogs have already been bred. Screening using standard methods cannot reveal a problem until the dog has been bred and the disease has been passed on to other dogs.

In 2018, a study of ARVC in human patients offered an indication of further boxer research by Cunningham. Almost all of the ARVC patients in the study had a type of antibody called anti-DSG2 that patients without ARVC did not. The study’s lead author, Robert Hamilton, a pediatric cardiologist specializing in ARVC in Ontario, Canada, shared the results with Cunningham for use in her boxing research.

“In addition to Hamilton’s first study in human patients, they also looked at a small population of boxer dogs with the disease. They found that almost all of these dogs had this antibody and the normal dogs they looked at did not, ”said Cunningham. “But that was a preliminary observational study in boxers. Given the high incidence of ARVC in the breed, there are many tests that show a dog is “normal” and does not have ARVC. “

To dig deeper, Cunningham and Dos Santos embarked on a clinical study with funds from the American College of Veterinary Internal Medicine (ACVIM) to identify the potential biomarker in boxers that, if successful, could potentially enable boxers to be screened earlier in life. This could help reduce the prevalence of the disease in the breed and allow for improved monitoring and treatment of individual pets.

The Cunningham and Dos Santos study looked at larger numbers of boxers – twenty dogs with ARVC and twenty normal dogs – and they performed all of the tests necessary to make sure the dogs were not showing signs of ARVC, including heart monitors, echocardiograms, and blood counts . “Although the tests only show if there are signs of the disease at this point, we have taken dogs in at the age at which one would expect ARVC to start looking up when they did. Our affected dogs have very specific indications of ARVC, ”said Cunningham.

Boxers with ARVC are treated with medication, including drugs used to treat irregular heartbeat. Many boxers will respond well to medical treatment, Cunningham said, but the condition can be more difficult to control in some pets who may need multiple medications.

A great dog and a lasting present

One of those dogs was a boxer named Ajax. Ajax owner Kim Pallotta of Weston, Massachusetts first brought Ajax to Cummings Veterinary Medical Center years ago because he had problems with his knees. But the surgeon examining him heard an irregular heartbeat and called Cunningham over to see.

“Ajax was one of the tallest and most majestic boxers I’ve ever seen – not overweight, just tall,” said Cunningham. “He was walking around with ventricular tachycardia – frequent, premature heartbeats in a very fast rhythm. It could have been life-threatening at any time and he was completely asymptomatic for it. “

“Ajax was walking around with ventricular tachycardia - frequent, premature heartbeats at a very rapid rate.  It could have been life threatening at any time, ”said veterinary cardiologist Suzanne Cunningham.  Photo: Courtesy Kim PallottaAjax also had an enlarged heart and needed many medical adjustments over the years after his diagnosis. Despite all efforts, Ajax suddenly passed away in 2018.

“He broke my heart,” said Pallotta. “But Dr. Cunningham held my hand the whole time, which was really wonderful. I’ve noticed that someone who works with animals and grapples with sad situations on a daily basis can still have so much compassion. “

Pallotta wanted to honor Ajax and help other boxer owners, so she started a fund to commemorate Ajax. ARVC and other medications and treatments for heart disease can be expensive, she noted, and some of the funding could be used to help homeowners who might otherwise not be able to afford care.

“I felt like I was really lucky to stumble upon someone who was actually doing research, and they’ve given me the past few years with him. Ajax had a lot of fans and that will help keep his memory alive, ”she said.

The funding also allowed Cunningham and Dos Santos to advance their research and purchase new diagnostic software that allows them to use ultrasound to get a 3D view of a dog’s heart.

“We can collect different views of the heart in a single stroke and then reconstruct the heart with special software,” said Dos Santos. “This gives us better views and measurements of heart size and function, especially the right ventricle, where the disease usually affects boxers.”

“It was worth it in many ways,” said Dos Santos. From a diagnostic perspective, imaging technology will expand cardiologists’ understanding of how the right ventricle functions in normal boxers and those with ARVC. From an educational perspective, he said, “students have access to an image that they would not see anywhere else.”

Angela Nelson can be reached at [email protected]

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