Cardiac autonomic modulation evaluated by heart interval variability is unaltered but subtly widespread in the indeterminate Chagas' disease

Background: Cardiac autonomic function in the indeterminate chronic form of Chagas' disease deserves better clearing-up and understanding, since the existing findings are scarce and controversial. This work analyzed the short-term heart interval variability in order to verify the cardiac autonomic modulation in indeterminate Chagas' disease subjects examined in a Brazilian endemic area. Methods: Variability in time and frequency domain of 5-minute electrocardiogram (ECG) series of R-R intervals in supine and active standing positions were obtained from 18 age-, gender-, body mass index, lifestyle-, and physical activity-matched chagasics and 18 control healthy subjects examined in Agua Comprida city, MG, Brazil. Mann-Whitney test was used for analysis of the data and spread of the individual indices in both groups. Results: The median of the all variability indices in the chagasic group were statistically similar (P = 0.17-0.87) to that in the control group. A wide dispersion of the almost all individual indices values, ranging from normal to variably reduced or increased ones, was noted in the majority of the chagasics in relation to the control interquartile range, in both postural positions. Conclusion: As a group, indeterminate Chagas' disease subjects showed unaltered short-term heart interval variability. Individual somewhat widespread of majority of time- and frequency-domain indices, from depressed to exacerbated ones appears to exist. This conforms to a variable cardiac autonomic modulation in this form of disease, suggesting that the majority of chagasics has no lesions, and a minority has subtle lesions of the efferent innervation-sinus node complex.