Amiodarone-related thyroid dysfunction and associated outcomes in patients with heart failure - a matched case-control study

Abstract Aim The association between amiodarone-related thyroid dysfunction and the risk of worsening heart failure (HF) or death has been reported with conflicting results. Methods The study cohort was patients with HF and without a history of thyroid dysfunction (defined by medical treatment or diagnosis) who initiated treatment with amiodarone in the period 1996-2021. Within this cohort, those who developed thyroid dysfunction (cases) were identified and matched 1:3 on age, sex, calendar year, duration of HF, and time since initiation of amiodarone with patients (controls) from the same cohort and followed for the primary outcome of HF hospitalization or all-cause death at 1-year, assessed by Kaplan Meier curves and Cox regression models adjusted for ischemic heart disease, chronic kidney disease, malignancy, atrial fibrillation and ventricular tachycardia. Results The study cohort comprised 21,947 patients, of whom 4,137 (19%) developed thyroid dysfunction following initiation of amiodarone. After matching, the study population consisted of 4,063 cases (mean age 69 years, 68% men, 41.6% developed thyroid dysfunction within the first year after initiation of amiodarone) and 10,940 matched controls, (Figure 1). The index date was the date of thyroid dysfunction for cases, and for matched controls a date at a similar distance since amiodarone initiation. At 1-year follow-up, the primary outcome occurred in 1,543 (38.0%) cases and 3,681 (33.6%) matched controls (reference), adjusted hazard ratio (HR) 1.13 (95%, confidence interval CI 1.07-1.20), although this was solely driven by HF hospitalization (28.9% vs 21.8%; HR 1.32 (95% CI 1.23-1.41), whereas all-cause death was lower among cases (18.2% vs. 20.4%, HR 0.85 (95% CI 0.78-0.93), (Figure 2). Conclusions Among HF patients treated with amiodarone, the development of thyroid dysfunction was associated with an increased risk of HF hospitalization or all-cause death, but this was solely driven by the excess risk of HF hospitalization, whereas it was associated with a lower risk of all-cause death. The absence of excess mortality indicates that thyroid complications are manageable in this vulnerable population of patients with HF.Figure 1 Flowchart of the populationFigure 2 Cumulative risk