Serum reverse T₃ and amiodarone efficacy

Abstract

Summary:The use of serum reverse T, (rT,) levels in the assessment of amiodarone efficacy is controversial. We prospectively studied 10 patients with frequent ventricular ectopy and symptomatic ventricular tachycardia (VT) treated with amiodarone. Serial 24-h Holter monitor, thyroid function studies including serum rT,, and 12-lead electrocardiogram were performed on each patient at baseline, and at 1,4, 12, and 24 weeks of oral amiodarone therapy. Serial Holter monitors on therapy were analyzed for 100% suppression of VT, 90% suppression of couplets, and 85 % suppression of ventricular ectopic beats (VEBs) compared with baseline Holter, defining patient groups VT-, Co-, and VEB-, respectively. Lack of arrhythmia suppression to this degree defined groups as VT + , Co + , and VEB + . There were no statistically significant differences in rT, levels between VT + and VTgroups, Co + and Co -groups, or the VEB + and VEBgroups. VT suppression could not be predicted at any rT, level. We conclude that serum rT, is an insensitive means of assessing amiodarone efficacy.

Clinical and laboratory aspects of 3,3′,5′-triiodothyronine (reverse T3)

“…Amiodarone has the most profound effect and is best studied. Unfortunately, serum rT3 concentration does not correlate with the antiarrhythmic benefits of amiodarone 53 so cannot be used in this context. Autoimmune hypothyroidism is common following amiodarone treatment occurring in over 5% of patients treated.…”