Reverse T3 as a parameter of myocardial function impairment in heart failure.

Sick Euthyroid Syndrome (SES) has been defined as low T(3) levels in the presence of normal TSH concentrations. The purpose of this study was to assess the relationship between heart failure functional classes (NYHA) and the presence of SES, as well as to estimate an index of myocardial function impairment (MFI). Forty-six patients were evaluated and 66 clinical laboratory assessments were performed. Clinical laboratory assessment reports (CLAR) were categorized according to heart failure functional class. The levels of rT(3) and fT(3)/rT(3) ratios were significantly higher and lower in class IV, respectively. In all CLAR reviewed, rT(3) positively correlated with functional classes II, III and IV. By adding the mean of the rT3 values found in Group I to one SD, MFI was estimated as 0.47 µg/mL. In 24 of the 66 CLAR reviewed MFI>0.47 µg/mL. Of these 24 CLAR, 92% were in Group II, and 8% were in Group I. MFI was low in 42 CLAR; 74% in Group II and 26% in Group I. MFI and rT(3) levels could be used for the evaluation of the prognosis of patients with heart failure in addition to (or even replacing) NYHA functional classification given that rT(3)>MFI suggests that the patient has a 92% possibility to be in NYHA functional class III or IV.