Mini donkey successfully receives pacemaker to manage fatal heart condition

dvm360dvm360 October 2022
Volume 53
Issue 10
Pages: 19

First surgery of its kind in a large animal species at Cornell

Three-month-old Nix the miniature donkey was regularly collapsing because of a severe heart condition. To treat this usually fatal ailment, veterinarians at the Cornell University Hospital for Animals successfully implanted a pacemaker in her.

Nix the miniature donkey (Photo courtesy of Darcy Rose via  Cornell University College of Veterinary Medicine).

Nix the miniature donkey (Photo courtesy of Darcy Rose via Cornell University College of Veterinary Medicine).

Nix’s owners, Mindy and Carlton Lockwood, struggled to watch her suffer. “It was either do nothing and Nix would continue to get worse and possibly have a painful death — or the pacemaker,” expressed Mindy Lockwood, in a university release.1

Beginning in fall of 2020, Nix experienced collapsing episodes and lethargy at just several months old. The Lockwoods had their regular veterinarian, Joan Ayers, DVM, of Genesee Valley Veterinary Hospital, examine the miniature donkey on her farm in Canandaigua, New York, where Nix resides.

Ayers, in tandem with Lockwood and Barbara Delvescovo, DVM, MRCVS, DACVIM, clinical fellow in the Section of Large Animal Medicine at Cornell, worked together to diagnose Nix’s condition. Initially they thought she may have epilepsy or have suffered a traumatic injury to her neck or skull, but these conditions were ruled out.

In February 2022, Nix was falling again, now from a standing position, and she staggered even more when walking. “When she fell, she was dazed for a few seconds and then would get back up. Several times she fell and rolled out of the pasture fence, which caused us even more concern for her safety,” Carlton Lockwood said, in the release.

Nix was referred to Cornell, where veterinarians did an echocardiogram and placed an ECG on her, to record her heart’s rhythm. There, Nix’s care team diagnosed her with third degree atrioventricular block, meaning her atria and ventricles weren’t communicating, so her heart’s rhythm was very slow and irregular.1 There were frequent pauses of 20-30 seconds with no heartbeats or blood flow to her body, enlarging her heart. With a lack of blood to her brain or around her body for long periods, Nix was experiencing the clinical signs of this condition (ie, collapse, episodes of weakness, and severe exercise intolerance).

According to the release,there are 2 types of arrhythmias: physiological, meaning they happen normally when horses are relaxed but go away with stress, excitement or exercise; or pathological, meaning they are abnormal, dangerous, and can result in poor performance. Nix had pathological arrhythmia.

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

Because Nix is young and has no underlying problems, she was an excellent candidate for a pacemaker. Once discussed with the Lockwoods, they gave the care team the OK to give her this surgery.

In a collaborative effort between 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 various hospital staff members, the complex procedure to implant Nix’s pacemaker went successfully. “There are a few mini donkeys around the world with pacemakers, but certainly it’s not common,” Mitchell noted. “It was great teamwork.”

There was quick improvement after surgery and now Nix has enough blood flow to her brain to walk normally, without fainting or lethargy. After 7 to 9 years, the pacemaker must be replaced. In the meantime, it’s important Nix stays calm and has limited exercise. Dangers can arise if the pacemaker lead pulls out of the heart muscle or becomes infected. “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 added.

Annually, Nix will visit Cornell for rechecks, but currently she’s in a small pasture with her mom to keep her activity low while she gets better, Lockwood says. “She has been much more alert, she’s vocal and has her spunk back.”

At her recheck appointment this month, the pacemaker was working well and she had just a slight reaction to the pacemaker lead. She did have some skin problems, likely associated with biting flies, so she is remaining in the hospital a few days to receive intravenous antibiotics.

Her next recheck will be next month, but now the Lockwoods are happily celebrating Nix’s second birthday.


Cordova MG. Mini donkey gets big boost from pacemaker. Cornell University College of Veterinary Medicine. August 11, 2022. Accessed August 12, 2022.

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