Specializing in Canine and Feline Neurology and Neurosurgery for Over 30 Years

Answer: C. Second degree heart block.

Discussion: The patient was fitted with an event recorder which showed that the seizure episodes coincided with a heart block. The seizures are, therefore, likely cardiogenic and the infarcts caused by cerebral hypoxia secondary to hypotension rather than embolic phenomena. See event recorder tracing, below.

Event Monitor

Diagnosis: Complete heart block (presumed due to idiopathic fibrosis of the AV node), periods of 2nd degree heart block and atrial flutter -- secondary hypoxia induced seizure episodes.

Comment: AV block with associated bradycardia can cause exercise intolerance, weakness, right-sided congestive heart failure, syncope, and sudden death. In this patient, the bradychardia was non-responsive to treatment with atropine and placement of a cardiac pacemaker was necessary. Without a pacemaker, the arrythmia would likely have worsened and ultimately led to permanent brain damage and death.

Outcome: Since pacemaker implantation 10 months ago, the seizure episodes have resolved. Vestibular signs improved but very mild vestibular signs are detectable and will likely be permanent. Click on the video to see a clip of the follow-up examination shortly after pacemaker placement.