Cardiac changes in subclinical and overt hyperthyroid women: retrospective study

This retrospective and descriptive 4-year study was undertaken to describe cardiac changes in subclinical and overt hyperthyroidism.

We revised the charts of 386 consecutive cardiopathic women whose blood samples were referred to the Radioimmunoassay Laboratory to evaluate thyroid function from 1 January 1997 through 31 December 2000.

After excluding women because euthyroid or hypothyroid, or taking amiodarone and women with hypertension, rheumatic disease, myocardial infarction, a total of 31 hyperthyroid women were thus selected for the study: 19 with subclinical hyperthyroidism and 12 with overt hyperthyroidism. The prevalence of atrial fibrillation did not differ between subclinical (48%) and overt (67%) hyperthyroid women, as well as left atrial dimension; the latter was larger in hyperthyroid (27.8+/-7.8 cm(2)/m(2)) than in control women (18.9+/-2.8 cm(2)/m(2)) (P<0.001). In the subclinical and overt hyperthyroidism, the heart rate (HR) was increased and left ventricular end diastolic (LVED) volume was reduced; in addition, only in overt hyperthyroidism, left ventricular (LV) mass was increased. A significant correlation between LV mass and free triiodothyronine was found.

HR increase and LVED decrease, both in subclinical and overt hyperthyroidism, indicate a global impairment of diastolic heart performance, complicated in overt hyperthyroidism by LV concentric hypertrophy. So, in our opinion, subclinical hyperthyroidism, far from being considered a simple laboratory finding, in clinical practice should be taken into serious consideration.