Power Spectral Analysis of Cardiovascular Variabilities as a Marker of Sympathetic Drive in Heart Failure

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In the first project of this study, we have developed simultaneous analysis of spectral components of sympathetic nerve activity, heart rate, instantaneous lung volume, left ventricular pressure and its first derivative, left ventricular volume, and ventricular elastance. These methods were extended to transfer function analysis between neural and hemodynamic variables and time-frequency analysis (wavelet transform). The feasibility of these methods was confirmed by simulation study using composition of multiple sine waves. In the second project of this study, we have applied these system analysis into clinical settings. (1) Low frequency components of sympathetic nerve activity : Among low ferequency componets of muscle sympathetic nerve activity, the wave with 0.1Hz showed a high square coherence with heart rate and blood pressure indicating close relationship between these variables. (2) Transfer function analysis of cardiopulmonary regulation : Randomly broadened respiratory rate was used to characterize a complex link between respiration and left ventricular peak pressure. At frequency between 0.05 and 0.15Hz, variations of end-diastolic volume via respiration playd a predominant rolw in the pressure variation, while above 0.15 Hz, the change in intrathoracic pressure directly contributed to the respiratory fluctuation of left ventricular pressure. (3) Augmentation of sympathetic nervous activity during acute coronary occlusion : The time-frequency analysis revealed that heart rate and left ventricular peak pressure fluctuated while myocardial ischemia was provoked by acute coronary occlusion during balloon angioplasty in patients with angina pectoris. The hemodynamic oscillation around 0.1 Hz suggests an augmentation of sympathetic drive mediated through myocardial ischemia. These analysis would provide a new insight into dynamic cardiovascular regulation of autonomic nervous system in chronic heart failure.