Stress echocardiography in hyperthyroidism

Exertion symptoms occur frequently in subjects with hyperthyroidism. Using stress echocardiography, exercise capacity and global left ventricular func tion can be assessed noninvasively. To evaluate stress-induced changes in c ardiovascular function, 42 patients with untreated thyrotoxicosis were exam ined using exercise echocardiography. Studies were performed during hyperth yroidism, after treatment with propranolol, and after restoration of euthyr oidism. Twenty-two healthy subjects served as controls. Ergometry was perfo rmed with patients in a semisupine position using a continuous ramp protoco l starting at 20 watts/min. In contrast to control and euthyroidism, the ch ange in end-systolic volume index from rest to maximal exercise was lower i n hyperthyroidism. At rest, the stroke volume index, ejection fraction, and cardiac index were significantly increased in hyperthyroidism, but exhibit ed a blunted response to exercise, which normalized after restoration of eu thyroidism. Propranolol treatment also led to a significant increase of del ta (Delta) stroke volume index. Maximal work load and Delta 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 Delta stroke vol ume index, Delta ejection fraction, Delta heart rate, and maximal work load were significantly reduced in severe hyperthyroidism. Negative correlation s between free T-3 and diastolic blood pressure, maximal work load, Delta h eart rate, and Delta ejection fraction were noted. Thus, in hyperthyroidism , stress echocardiography revealed impaired chronotropic, contractile, and vasodilatatory cardiovascular reserves, which were reversible when euthyroi dism was restored.