Dysregulation of peripheral and central chemoreflex responses in Chagas' heart disease patients without heart failure

Background-The peripheral and central chemoreflexes are important autonomic mechanisms for regulating breathing and cardiovascular function. Although pathological inflammatory infiltration of the peripheral chemoreceptors and central nervous system has been reported in Chagas' disease, functional ev aluation of chemoreflexes has not yet been performed. Methods and Results-The hypothesis that chemoreflex function is altered in patients with Chagas' heart disease (CH) but normal left ventricle function was tested in 12 CH patients and 13 matched control subjects. The ventilat ory rate, minute ventilation, heart rate, mean arterial pressure, forearm b lood flow, forearm vascular resistance, and venous norepinephrine responses to hypoxia and hypercapnia were determined. During hypoxia, the decrease i n oxygen saturation was smaller in CH patients, despite a similar ventilato ry response between groups. Both groups showed an increase in heart rate du ring hypoxia, but this response was blunted in CH patients. Although the me an arterial pressure response to hypoxia was similar in both groups, forear m vascular resistance significantly decreased in control subjects while rem aining unchanged in CH patients. Moreover, a significant increase in plasma norepinephrine levels elicited by stimulation of peripheral chemoreceptors was observed only in the CH group. During hypercapnia, the increase in min ute ventilation was smaller in CH patients, who did not exhibit the increas e in norepinephrine observed in control subjects. Conclusions-These data suggest that CH potentiates respiratory, cardiovascu lar, and autonomic responses to peripheral chemoreceptor activation by hypo xia in patients with normal left ventricular function. The ventilatory and sympathetic responses to central chemoreceptor activation by hypercapnia, h owever, are significantly blunted.