METHODS: Plasma levels of the neurohumoral factors that regulate circulatory blood volume were determined in 18 patients with ME and 15 healthy subjects (Controls).
RESULTS: The echocardiographic examination revealed that the mean values for the left ventricular end-diastolic diameters, stroke volume index, and cardiac index as well as the mean blood pressure were all significantly smaller in the ME group than in the Controls. The mean plasma renin activity (1.6±1.0ng/ml/h vs. 2.5±1.5ng/ml/h, p=0.06) was considerably lower in the ME group than in the Controls. Both the mean plasma aldosterone (104±37pg/ml vs. 157±67pg/ml, p=0.004) and antidiuretic hormone (ADH) (2.2±1.0pg/ml vs. 3.3±1.5pg/ml, p=0.02) concentrations were significantly lower in the ME group than in the Controls. Desmopressin (120?g), a synthetic version of arginine vasopressin, was orally administered for five successive days to 10 patients with ME. In five patients (50%), the symptoms of orthostatic intolerance during a 10min active standing test were ameliorated in association with a significant increase in urinary osmotic pressure and decrease in heart rate. Furthermore, in five patients (50%), the performance status scores for the activities of daily living were improved.
CONCLUSIONS: Both the renin-aldosterone and ADH systems were down-regulated despite the existence of reduction in cardiac preload and output in patients with ME. Desmopressin improved symptoms in half of the patients.