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CLINICAL RESEARCH: HEART RHYTHM DISORDER

Amiodarone-Induced Thyrotoxicosis

Clinical Course and Predictors of Outcome

David Conen, MD^_*, Ludovic Melly^_*, Christoph Kaufmann, MD^_*, Stefan Bilz, MD, Peter Ammann, MD^_*, Beat Schaer, MD^_*, Christian Sticherling, MD^_*, Beat Muller, MD and Stefan Osswald, MD, FACC, FESC^_*,_*

^_* Department of Cardiology, University Hospital, Basel, Switzerland
Department of Endocrinology, Diabetes, and Clinical Nutrition, University Hospital, Basel, Switzerland.

Manuscript received August 23, 2006; revised manuscript received February 8, 2007, accepted February 12, 2007.

^_* Reprint requests and correspondence: Dr. Stefan Osswald, Cardiology, University Hospital, Petersgraben 4, 4031 Basel, Switzerland. (Email: sosswald{at}uhbs.ch).

Objectives: This study sought to determine the clinical course and predictors of long-term outcome in patients with documented amiodarone-induced thyrotoxicosis (AIT).

Background: Amiodarone-induced thyrotoxicosis is a condition that is difficult to manage, in particular because of the long half-life of amiodarone. Data on optimal treatment for AIT are scarce.

Methods: We performed a retrospective review among patients with documented AIT at a tertiary care center. Baseline characteristics, treatment received, laboratory parameters, and events during follow-up were evaluated. The predefined composite end point consisted of the following AIT-associated complications: death, heart transplantation, hospitalization for heart failure, myocardial infarction, stroke, hospitalization for arrhythmia management, or hospitalization for treatment complications.

Results: Eighty-four patients were included in the present analysis; 27 patients received prednisone for AIT. There was no difference in time to normalization of free thyroxine between those receiving and those not receiving prednisone. Long-term follow-up showed high morbidity and mortality; 47 patients (56%) reached the primary end point. Patients receiving prednisone had a worse outcome than those not receiving prednisone (p = 0.003). Although patients received prednisone for 84 ± 65 days, curves started to separate only 12 months after the initial diagnosis.

Conclusions: Patients with AIT have a high event rate during follow-up. Prednisone had no effect on time to normalization of thyroxine levels and was associated with an increased event rate. Importantly, AIT-related problems must be expected late, at a time when thyroid function is under control.

Abbreviations and Acronyms   AIT = amiodarone-induced thyrotoxicosis   fT4 = free thyroxine   IQR = interquartile range   T3 = triiodothyronine   TSH = thyroid-stimulating hormone

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