Aims: Chagas disease patients often present premature ventricular complexes (PVCs), depression of left ventricular ejection fraction (LVEF) and autonomic dysfunction, which is generally evaluated by heart rate variability (HRV) analysis. As frequent PVCs may complicate HRV computation, we measured heart rate turbulence (HRT) and evaluated the correlation between ejection fraction and HRT or HRV in Chagas disease.
Methods: We studied 30 patients (47+/-11 years, 20 men) with Chagas cardiomyopathy and left ventricular dilatation who underwent clinical evaluation, ejection fraction (EF: 45+/-14%) determination and 24-h Holter monitoring (median PVC=1781). In all patients, the standard deviation of normal RR intervals (SDNN), the square root of the mean square differences of successive RR intervals (RMSSD) and values of turbulence onset (TO) and turbulence slope (TS) were calculated.
Results: HRT indices were independent of mean RR interval and presented high correlation with EF: TO (-0.11+/-0.01%, r=-0.60, P<0.001) and TS (5.8+/-3.7 ms/RR-interval, r=0.73, P<0.001). Of HRV parameters, only SDNN, corrected for mean RR interval, showed a weak but not significant correlation with EF (r=0.41). The comparison of HRT/EF and HRV/EF correlation coefficients, indicated the presence of a significant difference (P=0.017).
Conclusions: HRT indices appear to correlate better with EF than SDNN in Chagas disease. Thus, an analysis based on heart rate transient adaptation seems to perform better than HRV in detecting the autonomic alterations that parallel left ventricular dysfunction in Chagas disease patients. The high number of PVCs observed in these patients further support the use of HRT methodology.