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

Yamamoto, Yoshiharu; Nakamura, Yoshihiko; Sato, Hajime; Yamamoto, Masayuki; Kato, Kazuzo; Hughson, Richard L.

doi:10.1152/ajpregu.1995.269.4.r830

Cited by 75 publications

(75 citation statements)

References 17 publications

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“…The fractal dimension has been found to be high in resting human HRV with high levels of PNS activity, and reduced under several physiological conditions associated with parasympathetic withdrawal and increased sympathetic activity, such as exercise (Yamamoto et al 1992). Additionally, fractal HRV dynamics have been found to be decreased by PNS blockade with atropine (Yamamoto et al 1995), but not by â_adrenergic blockade (Yamamoto & Hughson, 1994). Thus, the observed hypoxia-related decrease in the fractal dimension in this study likewise implicates vagal withdrawal in mediating the tachycardia response while sitting.…”

Section: Ic Hypoxia and Cardiac Vagal Control In Sittingsupporting

confidence: 48%

“…Highfrequency power normalised to the total (harmonic and fractal) spectral power (PhÏPt) was used as an indicator of PNS activity, while the indicator of SNS activity, or alternatively 'sympatho-vagal balance' was denoted by PlÏPh (Pomeranz et al 1985;Hughson et al 1994;Yamamoto & Hughson, 1994;Yamamoto et al 1996). The fractal component was plotted in a log-power versus logfrequency plane, with the spectral exponent (â) estimated as the slope (−â) of the linear regression of this plot (Yamamoto & Hughson, 1993, 1994Yamamoto et al 1995Yamamoto et al , 1996. From the value of the spectral exponent, the fractal dimension (DF) of the trail of HRV, thought to reflect the underlying complexity of cardiac autonomic control, was calculated as DF = 2Ï(â − 1) for 1 < â û 3.…”

Section: Experimental Protocolmentioning

confidence: 99%

“…This is consistent with a reduction in the fractal dimension. Several lines of evidence have implicated cardiac vagal, but not sympathetic outflow in mediating HRV fractal components (Yamamoto et al 1992(Yamamoto et al , 1995Yamamoto & Hughson, 1994). The fractal dimension has been found to be high in resting human HRV with high levels of PNS activity, and reduced under several physiological conditions associated with parasympathetic withdrawal and increased sympathetic activity, such as exercise (Yamamoto et al 1992).…”

Section: Ic Hypoxia and Cardiac Vagal Control In Sittingmentioning

confidence: 99%

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Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans

et al. 2000

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Neural mediation of the human cardiac response to isocapnic (IC) steady-state hypoxaemia was investigated using coarse-graining spectral analysis of heart rate variability (HRV). Six young adults were exposed in random order to a hypoxia or control protocol, in supine and sitting postures, while end-tidal PCOµ (PET,COµ) was clamped at resting eucapnic levels. An initial 11 min period of euoxia ( PET,Oµ 100 mmHg; 13.3 kPa) was followed by a 22 min exposure to hypoxia ( PET,Oµ 55 mmHg; 7.3 kPa), or continued euoxia (control). Harmonic and fractal powers of HRV were determined for the terminal 400 heart beats in each time period. Ventilation was stimulated (P < 0.05) and cardiac dynamics altered only by exposure to hypoxia. The cardiac interpulse interval was shortened (P < 0.001) similarly during hypoxia in both body positions. Vagally mediated highfrequency harmonic power (Ph) of HRV was decreased by hypoxia only in the supine position, while the fractal dimension, also linked to cardiac vagal control, was decreased in the sitting position (P < 0.05). However, lowfrequency harmonic power (Pl) and the HRV indicator of sympathetic activity (PlÏPh) were not altered by hypoxia in either position. These results suggest that, in humans, tachycardia induced by moderate IC hypoxaemia (arterial Oµ saturation Sa,Oµ 85 %) was mediated by vagal withdrawal, irrespective of body position and resting autonomic balance, while associated changes in HRV were positionally dependent .

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Section: Ic Hypoxia and Cardiac Vagal Control In Sittingsupporting

confidence: 48%

Section: Experimental Protocolmentioning

confidence: 99%

Section: Ic Hypoxia and Cardiac Vagal Control In Sittingmentioning

confidence: 99%

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Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans

et al. 2000

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“…According to many researchers, the increasing activity of the sympathetic nervous system leads to the changes in HRV nonlinear dynamics; it becomes less complex relative to the balanced state [22,28,[63][64][65][66]. Our data suggest that sympathetic activity decreases the SD1/SD2 ratio.…”

Section: Discussionmentioning

confidence: 56%

Informative Nature and Nonlinearity of Lagged Poincaré Plots Indices in Analysis of Heart Rate Variability

Койчубеков

Риклефс

Sorokina

et al. 2017

Entropy

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Lagged Poincaré plots have been successful in characterizing abnormal cardiac function. However, the current research practices do not favour any specific lag of Poincaré plots, thus complicating the comparison of results of different researchers in their analysis of heart rate of healthy subjects and patients. We researched the informative nature of lagged Poincaré plots in different states of the autonomic nervous system. It was tested in three models: different age groups, groups with different balance of autonomous regulation, and in hypertensive patients. Correlation analysis shows that for lag l = 6, SD1/SD2 has weak (r = 0.33) correlation with linear parameters of heart rate variability (HRV). For l more than 6 it displays even less correlation with linear parameters, but the changes in SD1/SD2 become statistically insignificant. Secondly, surrogate data tests show that the real SD1/SD2 is statistically different from its surrogate value and the conclusion could be made that the heart rhythm has nonlinear properties. Thirdly, the three models showed that for different functional states of the autonomic nervous system (ANS), SD1/SD2 ratio varied only for lags l = 5 and 6. All of this allow to us to give cautious recommendation to use SD1/SD2 with lags 5 and 6 as a nonlinear characteristic of HRV. The received data could be used as the basis for continuing the research in standardisation of nonlinear analytic methods.

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“…Second, Yamamoto and Hughson (31) reported only small changes in fractal measures of human HRV after ␤-adrenergic receptor blockade. In contrast, Yamamoto et al (32) found that the fractal component of HRV in humans is diminished appreciably after cardiac vagal blockade with atropine. These results suggest that cardiac vagal outflow is more important than cardiac sympathetic outflow in generating the fractal component of HRV in humans.…”

Section: Discussionmentioning

confidence: 86%

Fractal properties of human muscle sympathetic nerve activity

Fadel

Orer

Barman

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

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Muscle sympathetic nerve activity (MSNA) in resting humans is characterized by cardiacrelated bursts of variable amplitude that occur sporadically or in clusters. The present study was designed to characterize the fluctuations in the number of MSNA bursts, interburst interval, and burst amplitude recorded from the peroneal nerve of 15 awake, healthy human subjects. For this purpose, we used the Allan and Fano factor analysis and dispersional analysis to test whether the fluctuations were time-scale invariant (i.e., fractal) or random in occurrence. Specifically, we measured the slopes of the power laws in the Allan factor, Fano factor, and dispersional analysis curves. In addition, the Hurst exponent was calculated from the slope of the power law in the Allan factor curve. Whether the original time series contained fractal fluctuations was decided on the basis of a comparison of the values of these parameters with those for surrogate data blocks. The results can be summarized as follows. Fluctuations in the number of MSNA bursts and interburst interval were fractal in each of the subjects, and fluctuations in burst amplitude were fractal in four of the subjects. We also found that fluctuations in the number of heartbeats and heart period (R-R interval) were fractal in each of the subjects. These results demonstrate for the first time that apparently random fluctuations in human MSNA are, in fact, dictated by a time-scale-invariant process that imparts "long-term memory" to the sequence of cardiac-related bursts. Whether sympathetic outflow to the heart also is fractal and contributes to the fractal component of heart rate variability remains an open question.Allan factor; dispersional analysis; Fano factor; heart rate variability; long-range correlations; time-scale invariance MUSCLE SYMPATHETIC NERVE ACTIVITY (MSNA) in resting humans is characterized by cardiac-related bursts of variable amplitude that occur sporadically or in clusters (1,9,10,18,20). In some subjects, cardiac-related burst amplitude waxes and wanes on the time scale of the respiratory cycle (9, 10, 18, 23). Whether respiratory-related or not, a hallmark of human MSNA is the variability of cardiac-related burst amplitude and interburst interval. In general, the muscle nerve fails to generate a burst in a variable number of cardiac cycles, thus leading to an MSNA burst-to-cardiac cycle ratio that is typically Ͻ1.0 in healthy human subjects.The primary aim of the present study was to define the basis for the fluctuations in the number of MSNA bursts, interburst interval, and burst amplitude. Two possibilities were considered. First, the variabilities might be best described by a random process in which events are uncorrelated (6, 27). The second possibility is that long-range correlations exist among events. If such correlations extend over more than one time scale, the fluctuations would be best modeled as a time-scaleinvariant (i.e., fractal) process in which the present value of the measured property is related not only to recent events but al...

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

Cited by 75 publications

References 17 publications

Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans

Body position and cardiac dynamic and chronotropic responses to steady-state isocapnic hypoxaemia in humans

Informative Nature and Nonlinearity of Lagged Poincaré Plots Indices in Analysis of Heart Rate Variability

Fractal properties of human muscle sympathetic nerve activity

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