Kaya, a three-week-old miniature donkey, presented to her local veterinarian because of episodes of fainting.
The veterinarian performed a complete physical examination and heard dropped beats that he believed were associated with the fainting.
Additionally, he heard a systolic heart murmur. After an electrocardiogram confirmed an abnormal heart rhythm, the veterinarian referred Kaya to the William R Pritchard Veterinary Medical Teaching Hospital at UC Davis.
There, Kaya was seen by both the Large Animal Internal Medicine Service and the Cardiology Service. They learned that not only was Kaya experiencing fainting episodes, she was also an unusually quiet donkey baby. She never bucked or played like a normal baby.
When UC Davis veterinarians listened to her heart with a stethoscope, both her abnormal heart rhythm and the heart heart murmurs described by Kaya’s veterinarian were confirmed.
To understand the causes of these abnormal findings, both an electrocardiogram (ECG) and an echocardiogram (cardiac ultrasound) were performed.
The ECG showed an abnormal rhythm (arrhythmia) consistent with third-degree AV block, which is a failure of the inherent pace-keeping mechanism of the heart. The ultrasound showed that the mitral, tricuspid and aortic valves were slightly leaky but that the overall structure and size of the heart were normal.
Routine lab work ruled out infection or electrolyte disturbances as the underlying causes of the arrhythmia.
Given these findings, it was suspected that Kaya’s third-degree AV block might be congenital (present at birth as a result of hereditary or environmental influences).
To treat the arrhythmia, Kaya was placed under general anesthesia and a pacemaker was installed. The evidence of the pacemaker’s success was seen immediately, as Kaya bucked for the first time that evening!
There went some important considerations for Kaya’s health regarding the piacement of the pacemaker. First, given Kaya’s age, it was likely that she would outgrow her pacemaker and a second surgery would be required. Second, it was critical that the jugular vein used for the pacemaker placement would never be used to administer intravenous medications or to draw blood.
The first of these considerations proved to be true, as six months after her initial pacemaker was placed, Kaya needed to return for a second, larger pacemaker to be placed. Her second pacemaker surgery was uneventful and Kaya is a happy donkey again!
Reprinted from The Horse Report (March 2013) with permission from the Center for Equine Health, School of Veterinary Medicine, University of California, Davis.