Management:
While positive chronotropes (i.e. sympathomimetics, anticholinergics) may be administered, most dogs are not successfully managed by this type of therapy. The definitive treatment for Sick Sinus Syndrome is implantation of a permanent artificial pacemaker. Furthermore, the severity of Musette’s pauses and the frequency of the collapse episodes warrant prompt pacemaker therapy. The pacemaker will rescue the heart from long pauses that would otherwise cause weakness or syncope, thus abolishing the clinical signs. The pacemaker will be inhibited by the heart’s inherent sinus (or otherwise) rhythm and will only discharge after a specifically programmed length of time (i.e. a pause of a particular length). Musette underwent successful pacemaker implantation and her clinical signs resolved. See Musette’s post-operative electrocardiogram Rhythm page.
In dogs, pacemaker implantation is usually performed transvenously. That is, a lead is passed down the jugular vein and into the right ventricle via a small incision in the neck over the jugular vein. The pacemaker (pulse generator) attached to the lead is placed subcutaneously in the neck. Post-operative radiographs: Lateral view and Dorsal-ventral view.
Prognosis:
With successful pacemaker implantation, the prognosis for sick sinus syndrome is excellent. Patients generally live into old age and succumb to other unrelated geriatric problems. Occasionally a dog may outlive the battery life of the pacemaker (battery life is generally 7 years), in which case the pulse generator in the neck is simply replaced. Proper periodic monitoring should predict the onset of battery failure.
Some complications of pacemaker therapy include seroma formation around the pacemaker, lead dislodgement, lead fracture, implant infection, and most serious, death during the implantation procedure (typically during that period when the patient is under the influence of some anesthetic drug but not yet paced). All of these complications are very rare.
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