When Graffiti’s heart rate soared to more than 240 beats per minute during simple exercises, the horse’s owner knew she needed to get to OSU’s Lois Bates Acheson Veterinary Teaching Hospital immediately.
The 17-year-old Latvian warmblood gelding had been successfully treated for an irregular heart rhythm called atrial fibrillation at OSU in 2023, but the problem resurfaced after he’d been stable on medication for 18 months, making it unsafe for him to continue doing dressage with owner Cyndy Kagan.
Luckily for Graffiti, OSU veterinarian Dr. Erica McKenzie has spent the past several years studying cutting-edge equine cardiology techniques and knew the best option was a transvenous equine cardioversion (TVEC for short). It was the first time the procedure had been performed at OSU or anywhere in Oregon.
“It is inherently a simple process that has a high success rate, so that appealed to me,” said McKenzie, a large animal internal medicine doctor and professor in OSU’s Carlson College of Veterinary Medicine.
That “simple” process still involved a 25-page checklist and coordination with almost every unit in the veterinary hospital, including cardiology, anesthesiology, radiology and internal medicine. The procedure also included a visiting cardiologist, Dr. JoAnn Slack from the New Bolton Center at the University of Pennsylvania School of Veterinary Medicine, who shared her expertise in TVEC with the OSU team. McKenzie studied with Slack in Pennsylvania last year.
“I was really thrilled with how smoothly everything went, how well everyone collaborated and how the different expertise that was available could make this a successful procedure,” McKenzie said.
In a healthy heart — equine or human — there’s a small area of cardiac tissue called a sinus node that is responsible for discharging electrical impulses to create a normal heart rate. This allows both the right and left atria of the heart to contract in unison and pump blood into the ventricles.
But in atrial fibrillation, the sinus node has lost control of the pattern, and the atria are stuck shaking without generating any contraction or delivering blood to the rest of the heart. In daily life, horses tolerate AFib better than humans do, but it can still create dangerous conditions when they engage in relatively mild exercise.
In 2023, McKenzie and the rest of the OSU veterinary team addressed Graffiti’s first bout of AFib with medication, but it had significant side effects. Plus, the cost of that medication recently increased tenfold. So when Graffiti’s problem recurred, McKenzie opted instead for a TVEC, which has a 90-95% success rate at “converting” a horse’s heart rate back into a normal sinus rhythm, but requires general anesthesia.
The procedure is almost like using a defibrillator on the inside of the horse’s body. Two extremely long catheters are carefully inserted through an incision in the jugular vein, reaching down into the left pulmonary artery and the right atrium of the heart. Doctors then administer powerful electrical shocks to the heart using a medical defibrillator connected to the catheters, aiming to momentarily stop electrical activity in the atria and then restart it in a correct, synchronized rhythm under control of the sinus node.
Graffiti received nine shocks, totaling 2,800 joules, and his rhythm converted to normal shortly after the ninth shock. McKenzie even livestreamed the electrocardiogram via Zoom so doctors and students who couldn’t watch the procedure in person could still observe how the team delivered the shocks, perfectly synched around Graffiti’s heartbeat to ensure they were delivered at safe points.
“Graffiti had an incredibly smooth recovery, thanks to our anesthesia team,” McKenzie said. “He’s a really sensible horse and we’re so proud of him for recovering so carefully after we got him cardioverted.”
Graffiti will be on medication for the foreseeable future to maintain his normal cardiac rhythm. If his AFib does return, he can be retired and live out his life in ease, McKenzie said.
Kagan had only had Graffiti for a year before his AFib first presented. She says she’s grateful for how OSU’s veterinary team talked her through the treatment process and the TVEC procedure, and that she didn’t have to ship him to another state to receive care.
“The trust is there. I never questioned that he was in really good hands and they’re doing everything they can for him,” Kagan said. “That’s not something every large animal hospital has.”
McKenzie has now led three TVEC procedures at the teaching hospital, all during spring 2025, and says it’s important that clients have access to different treatment options in the region, as the next-closest veterinary hospital to offer TVEC is at Washington State University.
“Being in a higher education environment where we can bring all these experts and their expertise together to perform something like this is really remarkable,” she said “I’ve worked at OSU for 20 years at this point. We really are a center of excellence in terms of being able to provide very advanced procedures that our clients and animals benefit from, and also for our students to be able to see the current state of the field and what you can do in veterinary practice.”
Kagan and Graffiti are thankful for that, too.
“We get another chance, and hopefully it’s a long one,” Kagan said. “He’s a great guy, he’s a buddy, and he deserves a good, healthy retirement when that time comes.”
Graffiti will be on medication for the foreseeable future to maintain his normal cardiac rhythm. If his AFib does return, he can be retired and live out his life in ease, McKenzie said.
Kagan had only had Graffiti for a year before his AFib first presented. She says she’s grateful for how OSU’s veterinary team talked her through the treatment process and the TVEC procedure, and that she didn’t have to ship him to another state to receive care.
“The trust is there. I never questioned that he was in really good hands and they’re doing everything they can for him,” Kagan said. “That’s not something every large animal hospital has.”
McKenzie has now led three TVEC procedures at the teaching hospital, all during spring 2025, and says it’s important that clients have access to different treatment options in the region, as the next-closest veterinary hospital to offer TVEC is at Washington State University.
“Being in a higher education environment where we can bring all these experts and their expertise together to perform something like this is really remarkable,” she said “I’ve worked at OSU for 20 years at this point. We really are a center of excellence in terms of being able to provide very advanced procedures that our clients and animals benefit from, and also for our students to be able to see the current state of the field and what you can do in veterinary practice.”
Kagan and Graffiti are thankful for that, too.
“We get another chance, and hopefully it’s a long one,” Kagan said. “He’s a great guy, he’s a buddy, and he deserves a good, healthy retirement when that time comes.”
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