experience and review of the literature

Thyroid hormone has multiple direct and indirect effects on the heart and the vasculature. Many signs and symptoms of thyroid dysfunction are manifest by the cardiovascular system. Furthermore, many cardiovascular diseases are adversely affected by the concomitant presence of either hyper- or hypothyroidism: it is still being debated whether these alterations are the consequence of increased cardiac workload alone or are due to the intrinsic properties of thyroid hormone. There are three potential mechanisms by which thyroid hormone might exert a cardiovascular action: (1) direct effects at the cellular level (inotropic and chronotropic effect); (2) interaction with the sympathetic nervous system; and (3) alteration of the peripheral circulation through changes in preload, afterload and energy metabolism. We treated 54 adult and seven pediatric patients suffering from severe low cardiac output in different clinical conditions with a mean bolus dosage of 2"1.5 mg h of T, followed by a continuous infusion ofy1 3 0.4"0.3 mg h for a mean duration of 48"12 h. In 45 patients, stabilization of the hemodynamic situation with a decrease iny1 inotropic support requirement was observed; however, in 11 patients no beneficial effects were observed. From this experience we suggest that T treatment may improve hemodynamics in a substantial proportion of cardiac and cardiosurgical patients in3 whom more conventional treatment is unsuccessful