Vagal dysautonomia in patients with Chagas disease and mortality: 14-year results of a population cohort of the elderly

Introduction: Great part of Chagas disease (ChD) mortality occurs due to ventricular arrhythmias, and autonomic function (AF) may predict unfavorable outcomes. We aimed to evaluate the predictive value of AF indexes in ChD patients.Methods: The Bambui Study of Aging is a prospective cohort of residents >= 60 years at study onset (1997), in the southeastern Brazilian city of Bambui (15,000 inhabitants). Consented participants underwent annual follow-up visits, and death certificates were tracked. AF was assessed by the maximum expiration on minimum inspiration (E:I) ratio during ECG acquisition and by heart rate variability indices: SDRR (standard deviation of adjacent RR intervals) and RMSSD (square root of the mean of the sum of squares of the differences between adjacent RR intervals)), calculated using a computer algorithm. Cox proportional hazards regression was performed to access the prognostic value of AF indexes, expressed as terciles, for all-cause mortality, after adjustment for demographic, clinical and ECG variables.Results: From 1742 qualifying residents, 1000 had valid AF tests, being 321 with ChD. Among these, median age was 68 (64-74) years, and 32.5% were men. In Cox survival analyses, only SDRR was associated with all-cause mortality in non-adjusted models: SDRR (hazard ratio (HR): 1.26 (95% CI 1.08-1.47), p < 0.001), E:I ratio (HR: 1.13 (95% CI 0,98-1.31), p = 0.10) and RMSSD (HR: 0.99 (0.86-1.16), p = 0.95). After adjustment for sex and age, none of the indexes remained as independent predictors.Conclusion: Among elderly patients with ChD, AF indexes available in this cohort were not independent predictors of 14-year mortality.