Amiodarone-Induced Thyrotoxicosis Is a Predictor of Adverse Cardiovascular Outcome
Journal of Clinical Endocrinology and Metabolism
Amiodarone-induced thyrotoxicosis (AIT) is a clinical condition that is notoriously difficult to manage; the relative risk of adverse cardiovascular events in these patients compared with euthyroid patients is largely unknown. Objective: We compared the clinical characteristics and major adverse cardiovascular events (MACE) in AIT and euthyroid patients. Method: Patients at a tertiary referral center who had been prescribed amiodarone for at least 3 months were retrospectively analyzed.
... y analyzed. Baseline clinical characteristics, laboratory parameters, and outcome events were evaluated. MACE was defined as cardiovascular mortality, myocardial infarction, stroke and heart failure, or ventricular arrhythmias that required hospitalization. Results: A total of 354 patients (61.8 Ϯ 14.1 yr; 64.7% male) with a mean follow-up of 48.6 Ϯ 26.7 months were studied. AIT, euthyroid status, and amiodarone-induced hypothyroidism were identified in 57 (16.1%), 224 (63.3%), and 73 (20.6%) patients, respectively. No differences in baseline clinical characteristics were observed between AIT and euthyroid patients. Nonetheless AIT patients demonstrated a higher MACE rate (31.6 vs. 10.7%, P Ͻ 0.01), mostly driven by a higher rate of ventricular arrhythmias that required admission (7.0 vs. 1.3%, P ϭ 0.03). Cox-regression multivariate analysis revealed that AIT (hazard ratio 2.68; confidence interval 1.53-4.68; P Ͻ 0.01) and left ventricular ejection fraction less than 45% (hazard ratio 2.52; confidence interval 1.43-4.42; P Ͻ 0.01) were independent predictors of MACE. Conclusion: In patients prescribed long-term amiodarone therapy, occurrence of AIT is associated with a 2.7-fold increased risk of MACE. Regular and close biochemical surveillance is thus advisable to identify and treat this high-risk group of patients. (J Clin Endocrinol Metab 94: 109 -114, 2009)