The following is a summary of “CORRELATION OF THYROID REPLACEMENT THERAPY WITH DEVELOPMENT OF ATRIAL FIBRILLATION IN ELDERLY POPULATION,” published in the March 2023 issue of Cardiology by Shrestha, et al.
Elderly patients (aged ≥65) undergoing thyroid replacement therapy are believed to be at greater risk of developing atrial fibrillation (AF). Although thyroid supplement doses are often adjusted to maximally suppress TSH levels in younger patients, such practice may have adverse effects on the elderly population.
For a study, researchers sought to investigate the association between maximal TSH suppression at higher doses of thyroid supplements and the risk of AF in elderly patients with hypothyroidism; we examined the TSH level trends of study participants. They followed 181 (≥65 yr) subjects from January 2012 through December 2019, excluding those with pre-existing AF, and grouped TSH into five levels (0-0.49, 0.50-0.99, 1.00-1.99, 2.00-2.99, and ≥ 3 mU/L).
For subjects with an AF event, they used the TSH level at the time of the event for analysis. Those with no AF events used the lowest TSH level during follow-up. They found that the mean TSH level among those who had an AF event was significantly higher than those with no AF event. Furthermore, hypertension (HTN), diabetes mellitus (DM), heart failure, and coronary artery disease (CAD) were all associated with an increased risk of AF. After controlling for HTN, DM, heart failure, CAD, obstructive sleep apnea (OSA), and obesity, we observed an increased hazard of 1.251 for each 1.0 unit rise in TSH when modeling time to AF event. Using TSH of 0-0.49 mU/L as the reference category, the hazard of an AF event among those with TSH ≥ 3 mU/L was approximately 4.5 times the hazard for those with TSH of 0-0.49 mU/L.
The findings contradicted the current understanding of an increased risk of AF in patients on thyroid supplements with doses titrated to suppress TSH maximally. They discovered that higher TSH levels are associated with an increased risk of developing AF, controlling for other known risk factors such as HTN, DM, heart failure, CAD, OSA, and obesity. However, the study was limited by a small sample size from a single institution, and larger, preferably prospective studies are needed to establish the correlation.