Cardiovascular autonomic dysfunction is found frequently in patients with Chagas disease, consistent with the autonomic nervous system abnormalities described earlier. Although such abnormalities are sometimes found in dilated cardiomyopathy of any cause, they are more frequent and more severe and develop earlier in Chagas disease. Reported abnormalities include blunted hemodynamic response to exercise,160 postural hypotension,161 and diminished heart rate variability,162 predominantly due to parasympathetic denervation. Abnormal responses to baroreflex testing,163 handgrip,164 atropine,165 and the Valsalva maneuver166 are frequently found at all stages of the disease. Plasma norepinephrine concentrations correlated with increasing degrees of autonomic dysfunction.167 Such abnormalities are sometimes found in the absence of other signs of heart disease, but they are more frequent when some degree of cardiac or gastrointestinal tract disease is present.168 The clinical significance of such autonomic abnormalities is uncertain, but some have suggested a relationship to the development of sudden cardiac death.169
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