Chronic
Chagas' disease produces pathologic changes of the cardiovascular, digestive, and autonomic nervous systems. In an attempt to elucidate the nature of the
dysautonomia in patients with
Chagas' disease, we measured plasma
norepinephrine levels, blood pressure, and heart rate, both supine and standing in 26 patients, and compared these values of patients classified according to three clinical subsets of cardiovascular manifestations with the values of nine normal volunteers and 16 patients with nonchagasic
heart failure. Results suggested (1) progressive blockade of the alpha receptor in patients with
Chagas' disease who have minimal clinical symptoms (group I) and in those who have ECG alterations without congestive symptoms (group II), as reflected by normal or raised plasma
norepinephrine levels without change of diastolic blood pressure during standing, which indicates absent postural reflexes; and (2) blockade associated with partial
denervation in patients with
Chagas' disease who have class III or IV
heart failure (group III), as suggested by a lower supine plasma
norepinephrine level and a fall in diastolic blood pressure in the upright position. The findings of reduced plasma
norepinephrine levels are in contrast to the elevated plasma
norepinephrine levels in patients without
Chagas' disease with class III and IV
heart failure who have sympathetic hyperactivity.