CARDIOLOGY

Owner of a Broken Heart: Donkey Receives Pacemaker

By Melanie Greaver Cordova

In the first surgery of its kind in a large animal species at Cornell, a 3-month-old miniature donkey named Nix underwent cardiac surgery to implant a pacemaker.

When Nix was just a few months old, she began having collapsing episodes and overall lethargy. Joan Ayers, DVM, of Genesee Valley Veterinary Hospital, examined the miniature donkey on her farm in Canandaigua, New York, where Nix lives with her parents, June and Hoot, a miniature donkey named Charlie, and a herd of goats.

Dr. Ayers, in consultation with the owners and Barbara Delvescovo, DVM, clinical fellow in the Section of Large Animal Medicine at Cornell, originally thought she might have epilepsy or have suffered some sort of traumatic injury to her neck or skull, but ruled these conditions out.

In February, Nix’s condition worsened. Nix was falling again, this time from a standing position, and she staggered even more while walking.

The Cornell veterinarians did an echocardiogram and diagnosed third-degree atrioventricular block—her atria and ventricles weren’t communicating, meaning her heart’s rhythm was very slow and irregular. There were frequent pauses of 20-30 seconds with no heartbeats or blood flow to her body, enlarging her heart. Without getting enough blood to her brain or around her body for long periods, Nix exhibited the classic clinical signs of this condition, including collapse, episodes of weakness and severe exercise intolerance.

Arrhythmias are divided into 2 categories, either physiological—meaning they happen normally when horses are relaxed but disappear with stress, excitement or exercise—or pathological, meaning they are abnormal, dangerous and can cause poor performance. Nix’s arrhythmia was the latter.

Imaging during Nix’s surgery.

Photo: Carol Jennings/CVM

“This is a pathological arrhythmia that we see pretty uncommonly in horses, but a little more occasionally in donkeys, and especially mini donkeys,” said Katharyn Mitchell, DVM, PhD, ACVIM (LAIM), assistant professor in the Section of Large Animal Medicine, who oversaw Nix’s case at Cornell.

Although it’s more common to see this type of arrhythmia in miniature donkeys, it is still rare. “Given the severity of the arrhythmia and the frequency of collapse, medication will not be effective, so we only had the choice of placing a pacemaker or euthanasia, given the high risk of continued self-trauma,” Dr. Mitchell said.

Given Nix’s age and her lack of other underlying problems, she was a great candidate for a pacemaker, according to Dr. Mitchell.

In a collaborative effort between Drs. Mitchell, Delvescovo from the large animal internal medicine service, Lawrence Santistevan, DVM, of the cardiology service, members of the large animal soft tissue surgery service, the anesthesia service and multiple hospital staff members, the complicated procedure to implant Nix’s pacemaker went well.

“There are a few mini donkeys around the world with pacemakers, but certainly it’s not common,” Mitchell said. ”It was great teamwork.”

Nix’s care team noticed immediate improvement after surgery—now the miniature donkey had enough blood flow to her brain to let her walk normally, without any fainting episodes or lethargy. The pacemaker battery will need replacing after approximately seven to nine years, but if the device continues to work well, Nix will live a normal life. In the short-term, it is imperative that Nix remain calm and have limited exercise. If the pacemaker lead pulls out of the heart muscle or becomes infected, both would be hazardous to her health.

“We will keep her calm for the first month to lower these risks, and if everything looks okay, then we will increase the pacemaker’s rate a little bit so she can get up some speed and play with her mum in the paddock,” Mitchell said.

At Nix’s recheck appointment this month, the pacemaker was working well, and her heart had only a mild reaction to the pacemaker lead.

Originally published on the Cornell website https://www. vet.cornell.edu/news/20220811/mini-donkey-gets-bigboost-pacemaker. It was edited for style.