Exit block in myxedema, treated effectively by thyroid hormone therapy

Area of Science:

• Cardiology
• Endocrinology

Background:

• Pervenous pacemakers are implanted for cardiac rhythm management, such as in sick sinus syndrome.
• Exit block, a failure of pacemaker stimulation, can occur post-implantation.

Observation:

• A 71-year-old female developed pacemaker exit block one year after pervenous pacemaker implantation for sick sinus syndrome.
• The exit block presented as a high pacing threshold, likely secondary to severe myxedema.

Findings:

• Thyroid hormone replacement therapy led to a normal pacing threshold by the seventh day.
• One-year follow-up confirmed effective myxedema control and normal pacemaker system function.

Implications:

• Severe myxedema can cause reversible pacemaker exit block by increasing pacing thresholds.
• This case highlights the importance of considering metabolic factors, like hypothyroidism, in pacemaker dysfunction.