Moutzouri, Elisavet; Lyko, Christina; Feller, Martin; Blum, Manuel Raphael; Adam, Luise; Blum, Steffen; Aeschbacher, Stefanie; Fischer, Urs; Roten, Laurent; Del Giovane, Cinzia; Meyer-Zuern, Christine S; Conte, Giulio; Bonati, Leo H; Moschovitis, Giorgio; Kuehne, Michael; Beer, Juerg; Aujesky, Drahomir; Osswald, Stefan; Conen, David and Rodondi, Nicolas (2021). Subclinical Thyroid Function and Cardiovascular Events in patients with Atrial Fibrillation. European journal of endocrinology, 185(3), pp. 375-385. BioScientifica Ltd. 10.1530/EJE-20-1442
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OBJECTIVE
To evaluate if subclinical thyroid dysfunction is associated with cardiovascular (CV) risk in patients with atrial fibrillation (AF).
METHODS
Swiss-AF is a prospective cohort of community-dwelling participants aged ≥ 65 years with AF. Primary outcome was a composite endpoint of CV events (myocardial infarctions, stroke/transitory ischemic events, systemic embolism, heart failure (HF) hospitalizations, CV deaths). Secondary outcomes were component endpoints, total mortality and AF-progression. Exposures were thyroid dysfunction categories, TSH and fT4. Sensitivity analyses were performed for amiodarone use, thyroid hormones use and competing events.
RESULTS
2415 patients were included (mean age 73.2 years; 27% women). 196 (8.4%) had subclinical hypothyroidism and 53 (2.3%) subclinical hyperthyroidism. Subclinical thyroid dysfunction was not associated with CV events, during a median follow-up of 2.1 years (max 5 years): age- and sex- adjusted hazard ratio (adjHR) of 0.99 (95% confidence interval (CI) 0.69-1.41) for subclinical hypothyroidism; and 0.55 (95%CI 0.23-1.32) for subclinical hyperthyroidism. Results remained robust following multivariable adjustment and sensitivity analyses. In euthyroid patients, fT4 levels were associated with an increased risk for the composite endpoint and HF (adjHR 1.46 95%CI 1.04- 2.05; adjHR 1.70 95%CI 1.08-2.66, respectively, for the highest quintile versus the middle quintile). Results remained similar following multivariable adjustment. Results remained significant for HF in sensitivity analyses. No association between subclinical thyroid dysfunction and total mortality or AF-progression was found.
CONCLUSIONS
Subclinical hypothyroidism was not associated with increased CV risk in AF patients. Higher levels of fT4 with normal TSH were associated with higher risk for HF.