Atrial lead dysfunction: an unusual feature of hypothyroidism.

Hypothyroidism is known to have a multitude of cardiac electrophysiologic effects, including bradycardia, atrioventricular block, prolonged QT interval, and elevated ventricular pacing thresholds. We report the case of a 36-year-old woman who presented with isolated dysfunction of her atrial pacemaker lead, which reversed with thyroid hormone replacement.