An Unusual Cause of High Threshold Values at Pacemaker Implantation

Abstract

An 81-year old man with third-degree AV block and weakness underwent an unsuccessful attempt to DDD pacemaker implant caused by hypothyroidism. Administration of thyroxin until he was euthyroid permitted implantation with normal stimulation thresholds.

Atrial Lead Dysfunction: An Unusual Feature of Hypothyroidism

“…5,6 Hypothyroidism causing myxedema cardiomyopathy has been reported to lead to increased ventricular pacing thresholds, an effect that is reversible with thyroid hormone replacement. [7][8][9] To our knowledge, hypothyroidism causing a selective increase in the atrial pacing threshold has not previously been described. The slowly improving pacing threshold with thyroid PACE, Vol.…”

Pacemaker Troubleshooting and Follow-up

“…Use of newer devices that can measure the capture threshold on a beat-to-beat or periodic basis can reduce the need for these higher outputs, yet provide the safety needed for the patient should the threshold rise. Any severe metabolic or electrolyte derangement can lead to acute threshold changes [177][178][179][180][181][182][183][184][185][186][187][188] (Box 29-10). The threshold may rise steadily over time until noncapture occurs or until the threshold exceeds the pacemaker's maximum output, typically referred to as exit block.…”

Emergency pacemaker implantation in acromegaly

“…Bradycardia is a common sign of hypothyroidism as well. In a single case, a hypothyroid man with third-degree AV block underwent an unsuccessful attempt to DDD pacemaker implant, however, only after administration of thyroxin until he was euthyroid permitted implantation with normal stimulation thresholds [8]. In acromegaly, several sinus, nodal, or ventricular conduction abnormalities leading to permanent pacemaker implantation have been described in a few cases; third-degree AV block has been reported in one single case [9].…”