Parasympathetic dysautonomia precedes left ventricular systolic dysfunction in Chagas disease

Background Parasympathetic dysautonomia is an established feature of advanc ed Chagas cardiomyopathy. How ever, in the absence of cardiac involvement, the presence of vagal dysfunction remains controversial. In a cross-section al study, we compared patients with Chagas disease without cardiac involvem ent and healthy individuals by three different methods to determine whether vagal dysfunction is present in the early phase of Chagas disease. Methods Sixty-one patients with Chagas disease without cardiac involvement and 38 controls were submitted to respiratory sinus arrhythmia test and 24- hour Holter monitoring. Vagal heart influences were assessed by the expirat ory/inspiratory (E/I) ratio, time-domain indexes of heart rate variability (HRV), and by the quantification of a S-dimensional return map. Results The two groups were comparable in terms of left ventricular ejectio n fraction and left ventricular end-diastolic dimension. Compared with the control group, patients with Chagas disease had significantly lower values of the E/I ratio (mean +/- SD: 1.38 +/- 0.02 and 1.25 +/- 0.02, P < .004) a nd short-term indexes of HRV (median [interquartile range]-rMSSD: 23 [18-27 ] and 17 [13-23], P = .00; pNN50: 11 [7-17] and 6 [2-12], P = .00). P-3, a beat-to-beat HRV index derived from the 3-dimensional return map, also was significantly reduced in the Chagas disease group (mean +/- SD: 118 +/- 5 v s 100 +/- 4, P = .00). None of these indexes of vagal heart control were si gnificantly correlated with left ventricular function or to the presence of esophageal radiologic abnormalities. Conclusion Parasympathetic dysautonomia is an independent and early phenome non in Chagas disease and may precede left ventricular systolic dysfunction .