Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Cardiomiopatia Chagásica/fisiopatologia , Sistema de Condução Cardíaco/fisiopatologia , Insuficiência Cardíaca/fisiopatologia , Arritmias Cardíacas/fisiopatologia , Pressão Sanguínea , Eletrocardiografia , Frequência Cardíaca , Humanos , Postura , Pressorreceptores/fisiologia , Valores de Referência , Manobra de ValsalvaRESUMO
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.
Assuntos
Doenças do Sistema Nervoso Autônomo/diagnóstico , Cardiomiopatia Chagásica/sangue , Doença de Chagas/sangue , Norepinefrina/sangue , Adulto , Doenças do Sistema Nervoso Autônomo/etiologia , Doenças do Sistema Nervoso Autônomo/fisiopatologia , Pressão Sanguínea , Cardiomiopatia Chagásica/fisiopatologia , Doença de Chagas/complicações , Doença de Chagas/fisiopatologia , Insuficiência Cardíaca/sangue , Frequência Cardíaca , Humanos , Pessoa de Meia-Idade , PosturaRESUMO
A 12-year-old boy with a norepinephrine-secreting pheochromocytoma that caused hypertension resistant to oral alpha adrenergic blockade is reported. Resistance to alpha adrenergic blocking agents developed when the patient's daily propranolol dosage was lowered from 10 to 1 mg/kg. Subsequently, alpha methyl tyrosine, an inhibitor of tyrosine hydroxylase, the rate-limiting enzyme in catecholamine biosynthesis, controlled the patient's blood pressure and was associated with reduction in total urinary catecholamine excretion. Norepinephrine content of the tumor and uninvolved adrenal gland removal at surgery was reduced. These findings confirm that alpha methyl tyrosine inhibited in vivo synthesis of catecholamines.