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 evaluation of chemoreflexes has not yet been performed.


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 ventilatory rate, minute ventilation, heart rate, mean arterial pressure, forearm blood flow, forearm vascular resistance, and venous norepi-nephrine responses to hypoxia and hypercapnia were determined. During hypoxia, the decrease in oxygen saturation was smaller in CH patients, despite a similar ventilatory response between groups. Both groups showed an increase in heart rate during hypoxia, but this response was blunted in CH patients. Although the mean arterial pressure response to hypoxia was similar in both groups, forearm vascular resistance significantly decreased in control subjects while remaining 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 minute ventilation was smaller in CH patients, who did not exhibit the increase in norepinephrine observed in control subjects.


CONCLUSIONS
These data suggest that CH potentiates respiratory, cardiovascular, and autonomic responses to peripheral chemoreceptor activation by hypoxia in patients with normal left ventricular function. The ventilatory and sympathetic responses to central chemoreceptor activation by hypercapnia, however, are significantly blunted.
Soares Barreto-Filho
J A
JA
Hypertension Unit, Heart Institute, InCor, University of São Paulo, São Paulo, Brazil.
Consolim-Colombo
F M
FM
Ferreira Lopes
H
H
Martins Sobrinho
C R
CR
Guerra-Riccio
G M
GM
Krieger
E M
EM
D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D001783:Blood Flow Velocity; D001794:Blood Pressure; D019296:Capnography; D002598:Chagas Cardiomyopathy / Q000150:complications / Q000503:physiopathology*; D002628:Chemoreceptor Cells / Q000503:physiopathology*; D005260:Female; D005542:Forearm / Q000098:blood supply / Q000503:physiopathology; D006339:Heart Rate; D006801:Humans; D006935:Hypercapnia / Q000503:physiopathology; D018496:Hyperoxia; D000860:Hypoxia / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009638:Norepinephrine / Q000097:blood; D010092:Oximetry; D010523:Peripheral Nervous System Diseases / Q000150:complications / Q000175:diagnosis / Q000503:physiopathology*; D012123:Pulmonary Ventilation; D012021:Reflex, Abnormal; D014655:Vascular Resistance; D016277:Ventricular Function, Left
D009638:Norepinephrine