Autonomic dysfunction and anti-M2 and anti-β1 receptor antibodies in Chagas disease patients.

Background: Sudden death is the leading cause of death in Chagas' disease, affecting patients even in the early stages of the disease. The impairment of the autonomic nervous system in this disease has been recognized, as well as its potential as a trigger for malignant arrhythmias when associated with structural or metabolic changes.

Objective: We sought to identify, in Chagas patients with preserved systolic function, the impairment of the autonomic nervous system and its association with functionally active anti-m2 and anti-β1 receptor antibodies.

Methods: Using spectral analysis of RR variability during passive tilt test, chronic chagasic patients were compared with healthy controls matched for age. Subsequently, the association of autonomic dysfunction with functionally active antibodies with anti-m2 and anti-β1 action was investigated by the Langendorf method.

Results: We observed that patients with Chagas disease without ventricular dysfunction express parasympathetic activity against a vagal stimulus, however with less intensity compared to controls. Chagasic patients with anti-m2 or anti-β1 antibodies showed a further significant reduction of the vagal response during respiratory sinus arrhythmia, regardless of the presence of structural lesion. However, the association of both factors promoted response to vagal stimulation similar to that seen in Chagas disease without their presence.

Conclusion: The lower vagal reserve in Chagas patients with preserved function was associated with functionally active anti-m2 or anti-β1 antibodies, and not with the presence of structural heart lesion.