Prevalence of thyroid dysfunction in patients with acute atrial fibrillation attended at a cardiology emergency room.

CONTEXT Atrial fibrillation occurs frequently in patients with thyrotoxicosis, while it has low prevalence in adults of the general population. The prevalence of thyroid dysfunction in subjects with atrial fibrillation is 0 to 24%, a wide variation that is attributed to the different methodologies applied. However, continuous use of amiodarone in patients with previous atrial fibrillation may interfere with these prevalence rates. OBJECTIVE In this study, we present the prevalence of thyroid dysfunction in adult patients who presented at a cardiac emergency room with acute atrial fibrillation, using a sensitive thyroid-stimulating hormone (TSH) assay and triiodothyronine (T3) and thyroxine (T4) determination. TYPE OF STUDY Cross-sectional study. SETTING Emergency room of a tertiary care facility. PARTICIPANTS A total of 72 patients with atrial fibrillation who presented at the emergency room not more than 48 hours after its onset. PROCEDURES A standardized questionnaire and 12-lead electrocardiogram were applied, and T3, T4 and TSH were determined. MAIN MEASUREMENTS TSH, T3 and T4 determination. RESULTS Among these patients, 16.6% had altered thyroid function tests: 6.9% had hyperthyroidism, 5.6% hypothyroidism and 4.2% had increased T4 levels, by means of amiodarone use. CONCLUSION The high prevalence of thyroid dysfunction in our study, especially hyperthyroidism, suggests that routine thyroid testing with sensitive thyroid-stimulating hormone assay is required in patients with acute atrial fibrillation.