RESUMEN
The aim of this work was to determine the effect of aging and gender on plasma norepinephrine (NE) response to orthostatic stress. Fifty-six men and sixty women non-smokers, sedentary, non-obese, were studied at supine and standing positions. On the basis of the age of the subjects, they were divided into three groups of either men or women. Group A, young, range 17-34 years, Group B, middle-age, range 40-60 years, and Group C: senescent, range 61-91 years. Senescent subjects had the highest absolute supine values of NE and significant differences between women and men were found in groups B Men: 298 +/- 15 pg/mL; Women: 348 +/- 14 pg/mL), and C (M: 386 +/- 29 pg/mL; W: 473 +/- 19 pg/mL), but not between young (M: 246 +/- 21 pg/mL; W: 261 +/- 18 pg/mL). NE increased markedly in response to the orthostatic stress but the relative (percentage) increases were smaller in the older subjects perhaps related to their elevated baseline levels. The highest percent positive variation was observed in group A (M: 85%; W: 82%). The oldest group (C), had the lowest variation (M: 23%; W: 21%). The relative increases in NE responses were not different in men and women. The orthostatic-induced variation in NE was negatively related to aging in both men and women (M: r = -0.654; p < 0.0001; W: r = -0.557; p < 0.0001). It is concluded that orthostatic stress induced rise of blood NE is attenuated by age but does not appear to be dependent on gender.
Asunto(s)
Norepinefrina/sangre , Postura/fisiología , Estrés Fisiológico/sangre , Adolescente , Adulto , Factores de Edad , Anciano , Anciano de 80 o más Años , Presión Sanguínea , Femenino , Humanos , Masculino , Persona de Mediana Edad , Factores SexualesRESUMEN
The autonomic nervous system is abnormal in patients with advanced Chagas'heart disease. Most researchers consider these autonomic abnormalities as primary, specific and irreversible. However, when and why do these abnormalities appear in the natural history of Chagas'disease, is still the subject of intense controversy. Recent morphological and functional studies strongly suggest that, the sympathetic and the parasympathetic abnormalities, are preceded by myocardial damage and left ventricular dysfunction. Consequently, the cardiac parasympathetic abnormalities and the activation of the sympathetic and of the renin-angiotensin-aldosterone systems of chagasic patients are very likely secondary and partially reversible. Therefore, neurohormonal activation, as postulated by the neurogenic theory could contribute to the progression of myocardial damage and left ventricular dysfunction. Additional clinical investigations are necessary to clarify this important issue.
Asunto(s)
Sistema Nervioso Autónomo/fisiopatología , Cardiomiopatía Chagásica/fisiopatología , Cineangiografía , Frecuencia Cardíaca/fisiología , Humanos , Sistema Nervioso Parasimpático/fisiopatología , Sistema Renina-Angiotensina/fisiología , Respiración , Sistema Nervioso Simpático/fisiopatología , Disfunción Ventricular Izquierda/etiología , Disfunción Ventricular Izquierda/fisiopatologíaRESUMEN
In patients with coronary artery disease, the risk of sudden death is related to the degree of left ventricular dysfunction and to cardiac parasympathetic activity. The relation between these two consequences of myocardial infarction is still the matter of intense controversy. In this investigation, we have estimated the resting cardiac parasympathetic tone and assessed the left ventricular systolic function of 25 patients who had suffered an acute myocardial infarction. The absolute increase in heart rate recorded in the first 10 seconds of a programmed dynamic exercise, was considered as the resting cardiac parasympathetic tone or cardiac parasympathetic reserve. Twenty five age and sex-matched normal sedentary subjects were used as controls. Patients showed a significantly smaller increase in their heart rate (16 +/- 4 lats/min, M +/- DS) than the controls 32 +/- 5 P < 0.0001), during the first 10 seconds of exercise. Moreover, the absolute increase in heart rate was inversely related to the degree of left ventricular dilatation ( r = - 0.71, P < 0.0001) and directly related to the left ventricular ejection fraction (r = 0.84, P < 0.0001). In other words, those patients with larger left ventricles and depressed ventricular function had a more prominent reduction of their resting cardiac parasympathetic tone. These results indirectly suggest that, left ventricular size and function are indeed related to cardiac parasympathetic activity.