Abnormalities in fractal heart rate dynamics in chagas disease

Background and Methods: In order to study fractal HR dynamics in Chagas disease, we performed detrended fluctuation analysis (DFA) - along with analysis of power-law β slope (β index) and standard deviation of N-N intervals (SDNN) - in edited and unedited (with ventricular premature beats - VPBs, only in DFA analysis) series of R-R intervals from Holter monitoring of healthy controls (Group 0, n = 27) and Chagas disease patients with left ventricular (LV) ejection fraction >50% (Group 1, n = 137) and with LV ejection fraction 2 is altered both among the Chagas patients with and without LV dysfunction. The short-term scaling exponent α₁ was higher in Group 1 Chagas patients as compared to controls (P <0.01) and did not differ between Group 2 and controls. In unedited R-R interval series, α₁ was significantly reduced in Group 2 Chagas patients (0.55 ± 0.002) as compared to controls (0.90 ± 0.002) and Group 1 (0.91 ± 0.003) (P <0.001), but did not differ between Group 1 and controls. Similarly α₂ was lower in Group 2 compared to other groups (P <0.001). SDNN did not differ between the groups, but the β index derived from 1/f model was reduced both in Group 1 and 2 Chagas patients as compared to controls (P <0.01). There was strong correlation (rs = 0.82; P <0.001) between the β and α₂ index from edited series. There was an inverse correlation (rs =-0.63, P <0.01) between the number of VPBs and α₁ index of unedited series. Conclusions: The long-term fractal HR dynamics altered in chagasic patients with and without LV dysfunction could be an early sign of autonomic dysfunction. Patients with impaired LV function show marked alterations in short-term fractal HR dynamics toward more random behavior, mainly due to frequent ectopy. Prospective studies are necessary to define the value of these indices as predictors of death in Chagas disease.