triiodothyronine--reverse and Ventricular-Fibrillation

The relation of serum reverse T3 (rT3) to amiodarone efficacy and toxicity was studied in 31 patients with frequent and complex ventricular arrhythmias. Baseline studies included 48-hour Holter recordings and rT3 levels (normal 33 ng/dl or less). Amiodarone therapy was initiated with a 5 mg/kg infusion followed by 600 to 800 mg/day for 7 to 10 days, then 200 to 400 mg/day. Holters and rT3 levels were repeated every 1 to 3 months and amiodarone was titrated to achieve at least a 70% reduction in total ventricular premature complexes, at least a 90% reduction in couplets and abolition of ventricular tachycardia. The baseline rT3 level was 18 +/- 7 ng/dl (range 10 to 30) and patients were followed 12 +/- 9 months. Arrhythmia control was achieved in 25 patients (81%), including 21 patients with elevated rT3 levels (36 to 105 ng/dl) and 4 patients with normal rT3 (15 to 33 ng/dl). Six patients were uncontrolled with rT3 (27 to 90 ng/dl) and 14 patients had minor side effects with rT3 (27 to 123 ng/dl). Three of 4 patients in whom rT3 levels exceeded 130 ng/dl died suddenly (137 to 174 ng/dl before the event). Thus, amiodarone efficacy and minor toxicity occurs at rT3 levels less than 105 ng/dl and sudden death may be associated with levels greater than 130 ng/dl.

Topics: Aged; Amiodarone; Benzofurans; Coronary Disease; Death, Sudden; Drug Evaluation; Electrocardiography; Female; Follow-Up Studies; Humans; Male; Middle Aged; Monitoring, Physiologic; Thyroid Gland; Triiodothyronine, Reverse; Ventricular Fibrillation

Amiodarone, a widely used iodine-containing antiarrhythmic drug, has been shown to divert the peripheral metabolism of T4 towards rT3 than T3. In this prospective study we correlated the concentration of the peripheral thyroid hormones in serum with that of amiodarone. Fifteen euthyroid volunteers were studied, 5 men and 10 women, with a mean age of 64.2 yr, who suffered from various cardiac arrhythmias (atrial fibrillation or multiple ventricular extrasystoles). Serum amiodarone, T4, T3, rT3 and TSH were determined before and 3, 7, and 14 days after the administration of 400-600 mg amiodarone/day. There was a small increase in serum T4 and a suggestive decrease in serum T3. The increase in serum rT3 was significant, with p less than 0.05 for 3 days, p less than 0.01 for 7 days and p less than 0.005 for 14 days. There was a significant correlation between the level of serum amiodarone and the rise in serum rT3 (r = 0.385, p less than 0.05). The rise in rT3 is the main thyroid abnormality after amiodarone administration and may be used as a rough index of the serum concentration of this drug.

Topics: Aged; Amiodarone; Atrial Fibrillation; Benzofurans; Female; Humans; Male; Middle Aged; Thyrotropin; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse; Ventricular Fibrillation