Amiodarone-associated thyroid dysfunction: risk factors in adults with congenital heart disease

Amiodarone is widely used in adults with congenital heart disease, but no systematic study has been published on its effects on thyroid function in these patients. A retrospective study was performed to examine the frequency of amiodarone-associated thyroid dysfunction in adults with congenital heart disease and to identify any contributing factors.

All adults (16 to 60 years old) with congenital heart disease were identified from a database if they had no preexisting thyroid disease, had taken amiodarone for >/=6 months, and were currently followed up by 1 consultant (J.S.). Ninety-two patients were found and evaluated for thyroid status and cardiac complications. A case-control analysis was performed, with patients matched for duration of amiodarone therapy. Of the 92 patients (age, 34.9+/-10.2 years; range, 18 to 60 years), 36% developed thyroid dysfunction: 19 became hyperthyroid and 14 hypothyroid. Female sex and complex cyanotic heart disease were significant risk factors for developing thyroid dysfunction (odds ratios, 3.0 and 7.00; P=0.04 and 0.01, respectively). Previous Fontan-type surgery also appeared to be a risk factor for developing thyrotoxicosis (odds ratio, 4.0; P=0.17), and amiodarone >200 mg/d a risk factor for thyroid dysfunction (odds ratio, 4.0; P=0.60).

Amiodarone-associated thyroid dysfunction is common in adults with congenital heart disease. Women and those with complex cyanotic lesions are at particular risk, as patients may be who have had Fontan-type surgery or are taking >200 mg/d of amiodarone. Amiodarone should be used only when other antiarrhythmics are ineffective or contraindicated. Vigilance is required to detect and treat thyroid dysfunction.