On the fractal nature of heart rate variability in XXXX : effects of vagal blockade.

@entity1 @entity3897 @entity299
The purpose of the present study was to investigate the effects of the vagal blocker @entity3897 on the fractal nature of @entity1 heart rate variability (HRV) at rest. Approximately 10-min segments of beat-to-beat heartbeat intervals, i.e., HRV, of 10 normal subjects and 11 @entity299 @entity1 were measured before and after intravenous injection of 0.5-0.75 mg @entity3897 . HRV data were analyzed by coarse graining spectral analysis (Y. Yamamoto and R. L. Hughson, Physica 68D: 250-264, 1993) to break down their total power into harmonic and nonharmonic (fractal) components. The harmonic component was used to calculate the contribution of high (> 0.15 Hz)-frequency components to total HRV power (%HF). From the fractal component, the contribution of the @entity299 (%fractal), the spectral exponent beta, and Hurst scaling exponent (H) were calculated. For both normal subjects and cardiac @entity1 , @entity3897 resulted in significantly (P < 0.05) less mean HRV and significantly (P < 0.05) greater beta compared with control, whereas mean values for %fractal were as high as 70% and were not significantly (P > 0.05) different between @entity3897 and control. The mean value of H with @entity3897 was significantly (P < 0.05) greater than that for control. Directional changes in %HF and beta were consistent with only one exception for a @entity1 who had the smallest change in log %HF by @entity3897 . The normally irregular fractal pattern of resting HRV was decreased by @entity3897 as shown by the decrease in %HF and the increase in beta.(ABSTRACT TRUNCATED AT 250 WORDS)
