Fergus is a 13-year-old West Highland White terrier who presented to his regular veterinarian with intermittent syncopal episodes, which were increasing in frequency to three to four times a week. Fergus was a trick dog, and had featured on Australia’s Got Talent. However, more recently, any excitement would trigger a syncope event.
Fergus’ heart was failing to produce a normal heart rhythm with his sinus rhythm on a 24 hour Holter monitor demonstrating sinus arrest for up to 11 seconds several times each day—resulting in frequent collapsing episodes. Fergus would get excited, and after a period of time would appear to stumble over his own feet before collapsing.
An ECG indicated a heart rate of 68-76 bpm, with evidence of sinus arrest. An initial examination indicated severe bradycardia. Further examination indicated mild mitral valve disease and mild tricuspid valve disease, degenerative without remodelling, and advanced sinus node disease, consistent with Sick Sinus Syndrome (SSS).
Initial treatment with atropine didn’t elicit a response, so specialist cardiologist Dr Brad Gavaghan determined Fergus was a candidate for a pacemaker. This is not a common procedure in 13-year old patients.
Fergus returned for blood and urine testing, 24-hour Holter monitor (to exclude a tachydysrrhythmia component to the SSS) and abdominal ultrasound to exclude comorbidities that may affect the outcome of the procedure. In the meantime, he was given propantheline at 15 mg tabs: 1/2 tab every 8-12hrs in a bid to potentially reduce the length of the sinus arrest events. This medication does not typically produce a good result in the face of a lack of response to atropine. With the poor response to medication, surgery was the only option.
Ten medical professionals were involved in Fergus’ surgery, including expertise from a pacemaker programmer from the human field, a veterinary specialist cardiologist and cardiology resident, two anaesthetists from the University of Queensland Small Animal Hospital, a critical care specialist and numerous veterinary technicians and nurses.
With Fergus undergoing four hours of anaesthesia, there were many things that could have gone wrong. The surgery didn’t pass without complications due to the unpredictable sinus arrest events.
With any kind of anaesthetic drugs or opioids, the patient’s escape rhythm is at risk of just stopping. The solution is to fit a temporary pacemaker first under twilight sedation, and then proceed to a full general anaesthetic. Under twilight anaesthesia, a 5 Fr balloon-tipped temporary pacing catheter was inserted by the cardiologist via a jugular catheter (6Fr radial artery catheter /0.018 wire) utilising a modified Seldinger technique.
As a precaution, a defibrillator is set up with transthoracic pacing pads, so we can externally pace the heart if they have any periods of sinus arrests while the temporary pacing lead is being placed. That did happen, and we were able to urgently start externally pacing him to enable his heart to continue to beat.
It’s a long procedure. When placing the permanent pacemaker (which was done by VSS Specialist Cardiologist, Dr Brad Gavaghan) it goes in through the jugular vein under fluoroscopic guidance. Dr. Gavaghan then navigated it into exactly the right location and then the permanent lead tip is then screwed into the ventricular muscle.
The lead is connected to a generator/battery under the skin behind the shoulder, and the heart rate and output is calibrated by a pacemaker technician.
The recovery period is not very painful given this surgery is relatively non-invasive and only required two small skin incisions. Fergus has made an uneventful recovery. The heart’s pacing daytime rate’s set at a hundred and it automatically lowers the rate to 80 bpm at 10:00 PM each night at sleep time. The pacemaker has motion sensors that detect patient movement, increasing the HR up to 160 bpm depending on the level of activity.
Any infection has serious consequences as hardware is implanted both subcutaneously and within the heart, so Fergus was on antibiotics both pre- and post-operatively. Another risk is dislodgement of the lead tip, or loss of capture if we haven’t got the output of the pacemaker set correctly.
Postoperatively we monitor them very closely and keep them very quiet and calm that first night. Fergus has now got a normal life expectancy. The pacemaker battery lasts five years, so if Fergus continues to act like a 2 year old, he can have the generator replaced if he manages to wears out the battery!
Afterwards, he did tricks for us from his very large repertoire. He’d sit on his back legs and do little paw shakes and sit up. He was pretty cute.
DR ELLIE LEISTER BVSc FANZVCS
Dr Ellie Leister is the Pet Intensive Care Director at Animal Emergency Service’s Underwood practice.
In 2004, Dr. Leister spent four years in mixed practice in country NSW before sitting memberships and moving to England where she started to focus more on small animals and her passion for emergency and critical care started. Ellie has worked exclusively as a critical care veterinarian in the Pet Intensive Care Unit at VSS in Brisbane since returning in 2012. She manages a team of 20 people and the ICU operates 24/7.
The PICU is known nationally a one of the most well run and busiest critical care centers in the country. It manages very complex cardiology, oncology, medical and surgical cases as well as everyday emergencies.