Saving dogs with mitral valve disease while advancing human medicine

After his daughter’s dog was struck down by heart valve disease, UCHealth interventional cardiologist Dr. John Carroll teamed up with CSU veterinary professor to advance cardiology across species.
Feb. 12, 2019
dog sleeping on bed. mitra-valve disease in dogs, like humans, can make them more tired than usual.
Mango, who had mitral valve disease, sleeping on his owner’s bed. Photo courtesy of Grace Carroll.

Four years ago, Dr. John Carroll was helping his daughter, Grace, get ready to go back to college when the two noticed that Mango, her 5-pound Chihuahua, wasn’t his feisty self. Usually, 9-year-old Mango would be sunbathing or running around the yard. And as Grace packed her bags, she couldn’t help but wonder if something was wrong with her childhood pet.

On this day — and for the past few days — Mango had been coughing and making a “honking” noise, Grace explained. Mango also seemed breathless and exhausted.

They decided to visit their vet, who heard a heart murmur. An X-ray also showed Mango had an enlarged heart. The veterinarian referred them to a canine cardiologist.

Heart murmur? Breathlessness? Fatigue? Coughing? Carroll, an interventional cardiologist with UCHealth University of Colorado Hospital on the Anschutz Medical Campus, couldn’t believe what he was hearing. Was it possible that little Mango had some form of heart valve disease?

Carroll, who also is an interventionalist and professor for CU School of Medicine, specializes in cardiac catheterization and catheter-based therapies for diseased heart valves, holes in the heart, coronary artery disease and a variety of other novel therapies.

“This was an eye-opener for me,” Carroll said. “Here I was watching our own dog go through a disease process that I’d been diagnosing and treating for the past 35 years in the human world.”

Mango was diagnosed with mitral valve regurgitation. Each chamber of the heart has a one-way valve to keep blood from flowing backward. The mitral valve is between the left atrium and left ventricle. This valve can wear out over time and leak — called mitral regurgitation.

Treating mitral valve disease in dogs

About one in 10 dogs develops some form of heart disease during their lifetime.  Approximately 80 percent of these dogs end up with mitral valve insufficiency or regurgitation, according to The disease is more common in small dogs than large breeds.

In humans, mitral regurgitation is the most common type of moderate to severe heart valve disease among adults older than 55 in the United States, Carroll said. The disease’s occurrence increases with age, the same as with dogs, he added.

Mitral valve disease in dogs or humans doesn’t always present with symptoms but, when it does, patients often have a noticeable heart murmur and breathlessness and fatigue with normal activity.

dog with birthday hat on sitting in front of dog bone-shaped cake that says happy birthday.
Mango celebrates his 10th birthday a few weeks after discovering he has valvular heart disease. Photo courtesy of Grace Carroll.

When a human has a leaky valve it can often be fixed by repair or replacement of the mitral valve with open heart surgery or emerging transcatheter treatments. At UCHealth, a variety of transcatheter treatments for various forms of mitral valve disease are performed. UCHealth hospitals are also investigative sites for several up-and-coming transcatheter therapies, Carroll said.

“Unfortunately, they have not been re-engineered for use in small animals like Mango,” he said.

When Grace heard that Mango had heart valve disease, she was devastated. Mango lived a year longer but his lively personality and energy never returned. Just before his 11th birthday, he died.

“I had seen my dad put in a MitraClip the previous summer (2015),” Grace said of one of the innovative therapies. “The solution was right in front of us, but we couldn’t do it.”

Interventions fall behind for animals

“It raised thoughts in my mind, not only of what could be done for dogs, but on a broader scale, there are strong synergies between cardiology care in animals and humans, and let’s start looking into this seriously,” Carroll said.

Carroll then learned of a collaborative resource request from Dr. Brian Scansen, a veterinarian and associate professor of cardiology at Colorado State University’s College of Veterinary Medicine and Biomedical Sciences, in Fort Collins.

James L. Voss Veterinary Teaching Hospital at Colorado State University

Scansen was in the process of establishing interventional cardiology as a unique and advanced discipline within the school’s veterinary medicine program.

“Cardiology was here as a program and is a recognized specialty within veterinary medicine,” Scansen said. “But it was not subspecialized to the same extent that human cardiovascular programs are. Our vision was to build interventional cardiology into a unique subspecialty of cardiovascular care in veterinary medicine.”

Cardiology has expanded over the decades in the human realm and many doctors focus on subspecialties within cardiology, such as heart failure or transplants. Interventional cardiology focuses on procedures that improve how the heart may be performing, such as placing a stent to open a clogged artery or a device to repair a leaky valve. Traditional cardiac surgical operations involve opening up the chest while more recently, in the past several decades, interventional cardiologists perform catheter-based therapies. These less-invasive treatments use a catheter to thread a device through a vein to and inside the heart, where it is placed to correct the problem.

As part of advancing the CSU program, Scansen wanted to create a fellowship and open a new hybrid cardiac catheterization lab that would match up to any human lab doing these same interventional procedures.

“To develop this new and unique training program, it was key to be able to bounce ideas off someone with that level of experience and expertise,” Scansen said.

photo of Dr. Carroll
Dr. John Carroll, an interventional cardiologist with UCHealth University of Colorado Hospital on the Anschutz Medical Campus. Photo: UCHealth.
Photo of Dr Scansen
Brian Scansen, a veterinarian and associate professor of cardiology at James L. Voss Veterinary Teaching Hospital at Colorado State University. Photo courtesy of CSU.

And that’s when Carroll and Scansen got connected, more than three years ago.

Collaborating across species

“It’s been an evolving partnership,” Carroll said. “We had some major overlaps in our mission, one of which was the similar mission of training people to become interventional cardiologists in our respective domains of humans and animals.”

CSU’s interventional cardiology fellowship started in 2016 and is the first in the world, Scansen explained. Scansen and his fellows attended some of Carroll’s procedures at UCH. Much of what they needed to learn in animal health care is similar to human health care when it comes to procedures and safety, Carroll explained.

Carroll also visited CSU.

The first collaborative patient case

Scansen had a patient, a dog named Ricky, who had an atrial septal defect — a hole in the heart.

“We don’t see a lot of these in dogs, whereas he (Carroll) has seen thousands in humans,” Scansen said. “We’d had conversations in the past, so when this dog came up, I reached out to see if he was available.”

Carroll’s experience was instrumental. Carroll knew the tricks, as Scansen put it, in using the image-guiding technologies to correctly position the device that would plug the hole in Ricky’s heart.

“All of this is very standardized in human procedures but in its infancy in animal procedures,” Carroll said. “I have great respect for Brian (Scansen) and his colleagues in being on the forefront of developing these procedures in dogs, but also that they deal with so many different types of animals, each having unique anatomy, size, and pathophysiology of different cardiac abnormalities.”

surgeons performing surgery to treat mitral valve disease in dogs
Brian Scansen, a veterinarian and associate professor of cardiology at L. Voss Veterinary Teaching Hospital at Colorado State University, and his colleagues perform a catheter-based heart procedure, for things like mitral valve disease in dogs, in their state-of-art cardiac catheterization lab. Photo by Kellen Bakovich, Colorado State University.

Unmatched veterinary cath lab

To do these interventional procedures in animals — as well as to advance the practice as a whole in his industry — Scansen needed the very best and latest equipment.

Carroll again provided insight.

UCHealth has the longest standing structural heart program in Colorado, performing minimally-invasive procedures like MitraClip, Watchman and TAVR in its cardiac cath labs.

“We visited UCH to see what they had, what we might need and what we wouldn’t need, as well as how some equipment may be adapted for animals,” Scansen said.

Some of the more routine interventional heart procedures were already being done in animals before the creation of the new program, but Scansen wanted to move his subspecialty within veterinarian medicine to the next level.

“That required higher-level equipment in imaging, which means a better facility,” he said. “Now, thanks to the generosity of clients whose pets we have treated in the past, we have a cath lab that is as state-of-art as anything available to humans.”

With the lab and training in place, it is time to move to the next step, he explained.

Novel interventions

selfie of girl and dog
Grace Carroll with her childhood pet, Mango. Photo courtesy of Grace Carroll.

Carroll said he believes such collaborative partnerships, which aren’t standard, bring a broader “lessons learned” understanding into medicine that can sometimes move the field forward. With some animals having the same valve diseases found in humans, these collaborative relationships can spark new research into the genetic paths of those diseases, as well as technology and devices that could reach across species.

“We are hoping that we can develop and interface with the medical-device industry, where there is an unmet clinical need in these dogs,” Carroll said.

Currently, Scansen does about 120 catheter-based procedures per year in animals, mostly dogs. But these are the cases where interventions are available, he said, such as with Ricky, who got a device to close the hole in his heart and is doing well. With nearly 10 percent of all dogs developing valve disease, many more — like Mango — would benefit from new interventions not currently available to animals.

“There is technology commercially available for humans that requires minimal or no alteration for use in animals, but we need to grow our expertise and learn how best to adapt such technologies for animal anatomy because they are made for humans,” Scansen explained. “We are making those adjustments and have some things in development, but the next level is to push the boundaries as to what can be done to help animals with heart disease.”

Carroll said he sees these advancements also benefiting interventional cardiology for humans.

“These collaborations bring in fresh insight into doing things that didn’t previously exist,” he said. “I believe people in my profession will likewise see it’s not only relevant to their own pets, but to their clinical investigations. There is this lighting of the fire of collaboration by exposing people to things they’ve never even thought of. I want to expose the adult human cardiology community to heart disease in animals and its parallels.”

About the author

Kati Blocker has always been driven to learn and explore the world around her. And every day, as a writer for UCHealth, Kati meets inspiring people, learns about life-saving technology, and gets to know the amazing people who are saving lives each day. Even better, she gets to share their stories with the world.

As a journalism major at the University of Wyoming, Kati wrote for her college newspaper. She also studied abroad in Swansea, Wales, while simultaneously writing for a Colorado metaphysical newspaper.

After college, Kati was a reporter for the Montrose Daily Press and the Telluride Watch, covering education and health care in rural Colorado, as well as city news and business.

When she's not writing, Kati is creating her own stories with her husband Joel and their two young children.