CLINICAL STUDY Cardiovascular haemodynamics and cardiac autonomic control in patients with subclinical and overt hyperthyroidism

Objective: To characterize cardiac structure and function and cardiac autonomic control in patients with subclinical and overt hyperthyroidism. Design: Thirty patients with subclinical hyperthyroidism and 30 with overt disease were selected from patients never previously treated for endocrinological disease in the outpatient clinic of our institution. Twenty normal individuals were studied as control group. Methods: Left ventricular structure and function and cardiac autonomic control were evaluated, respectively, by two-dimensional Doppler echocardiography and by 24-h Holter recording with heart rate variability analysis. Results: Patients with overt hyperthyroidism showed greater values of left ventricular end-diastolic volume P, 0:05 and left ventricular mass \u85P, 0:05 than patients with subclinical disease. In addition, the mean velocity of left ventricular fibre shortening \u85P, 0:05 and left ventricular ejection fraction P, 0:05 were greater in patients with overt hyperthyroidism than in patients with subclinical disease. No difference in any of these parameters was detectable between normal subjects and patients with subclinical disease. The isovolumic relaxation period was shorter in patients wit