Though thyroid hormone abnormalities have been identified in many cardiac 
conditions, the role of thyroid hormones in congestive heart failure has not 
been well defined. In a population of patients with advanced heart failure, a 
reduction in triiodothyronine (T3) with an increase in reverse T3 was identified 
in many patients, with an abnormally low ratio of T3/reverse T3 being the 
strongest predictor of mortality. Normalization of thyroid indices appeared to 
be necessary for prolonged survival to occur. To address the concern of T3 
administration possibility exacerbating a hypermetabolic state, basal metabolic 
rate was measured in a group of advanced heart failure patients and was found to 
be generally within the normal range. A preliminary safety study of short-term 
intravenous T3 administration (bolus +/- 6 h infusion, total dose 0.15-2.7 
micrograms/kg) was then performed in 23 patients under hemodynamic and 
electrocardiographic monitoring. There were neither adverse events nor 
substantial hemodynamic changes, but some patients had an increase in cardiac 
output, consistent with a peripheral vasodilatory effect. With this foundation, 
further investigation into the possible role of T3 and its analogs in congestive 
heart failure therapy may be pursued.