RESUMEN
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.