Influence of L-thyroxine on cardiac function in athyreotic thyroid cancer patients--an echophonocardiographic study.

We have assessed left ventricular performance in twelve athyreotic patients by echophonocardiography during and after their follow-up investigations. Patients were investigated after 4 weeks without and after 2 as well as 4 weeks of therapy with 150-200 micrograms L-thyroxine (L-T4). At the end of 4 weeks withdrawal of L-T4 patients were severely hypothyroid in terms of T4 and thyrotropin (TSH) serum levels as well as total cholesterol plasma levels. In comparison to values obtained in 12 age and sex matched normal controls left ventricular preejection period was prolonged at that time point (110 +/- 20 vs. 90 +/- 20 (SD) ms, p less than 0.05) and the isovolumetric relaxation period (IVRP) was significantly lengthened (78 +/- 16 vs 54 +/- 10 ms, p less than 0.01). Left ventricular ejection phase indices (fractional shortening and mean velocity of circumferential fiber shortening) did not differ significantly from normal. Preejection period dropped to 90 +/- 20 ms (p less than 0.05) after 4 weeks of therapy with L-T4. IVRP decreased to 67 +/- 13 ms (p less than 0.01) but remained significantly prolonged compared to normal. Serum T4, TSH and plasma cholesterol were compatible with borderline hyperthyroidism at that thime point. Thus, systolic as well as diastolic left ventricular performance (especially during isovolumic phases) appear to respond rapidly to thyroid hormone deficiency of short duration and at least partly to resupplementation.