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Stress Echocardiography in Hyperthyroidism

Departments of Endocrinology/Metabolism, and Cardiology (S.W., S.M.K.), Gutenberg University Hospital, Mainz 55101, Germany; and the Echocardiography Laboratory, Division of Cardiology, Duke University Medical Center (T.J.R.), Durham, North Carolina 27710

Address all correspondence and requests for reprints to: Prof. George J. Kahaly, University Hospital, Building 303, Mainz 55101, Germany. E-mail: kahaly{at}endokrinologie.klinik.uni-mainz.de

Exertion symptoms occur frequently in subjects with hyperthyroidism. Using stress echocardiography, exercise capacity and global left ventricular function can be assessed noninvasively. To evaluate stress-induced changes in cardiovascular function, 42 patients with untreated thyrotoxicosis were examined using exercise echocardiography. Studies were performed during hyperthyroidism, after treatment with propranolol, and after restoration of euthyroidism. Twenty- two healthy subjects served as controls. Ergometry was performed with patients in a semisupine position using a continuous ramp protocol starting at 20 watts/min. In contrast to control and euthyroidism, the change in end-systolic volume index from rest to maximal exercise was lower in hyperthyroidism. At rest, the stroke volume index, ejection fraction, and cardiac index were significantly increased in hyperthyroidism, but exhibited a blunted response to exercise, which normalized after restoration of euthyroidism. Propranolol treatment also led to a significant increase of delta () stroke volume index. Maximal work load and heart rate were markedly lower in hyper- vs. euthyroidism. Compared to the control value, systemic vascular resistance was lowered by 36% in hyperthyroidism at rest, but no further decline was noted at maximal exercise. The stroke volume index, ejection fraction, heart rate, and maximal work load were significantly reduced in severe hyperthyroidism. Negative correlations between free T₃ and diastolic blood pressure, maximal work load, heart rate, and ejection fraction were noted. Thus, in hyperthyroidism, stress echocardiography revealed impaired chronotropic, contractile, and vasodilatatory cardiovascular reserves, which were reversible when euthyroidism was restored.

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