Thyrotoxicosis induced sick sinus syndrome: medical therapy may avoid permanent pacing.

A 65-year-old white female developed sick sinus syndrome associated with thyrotoxicosis which resolved upon achieving a euthyroid state, thus obviating the need for permanent pacemaker implantation. TSH was less than 0.1 ng/dL, and 24-hour iodine uptake was 28%. After correction of the hyperthyroid state with propylthiouracil and potassium iodine, sinoatrial pauses up to 6 seconds resolved over 10 days. A subsequent sinus node recovery time was normal and no symptoms recurred over 22 months.