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

在本研究的第一个项目中，我们开发了同步分析的频谱成分的交感神经活动，心率，瞬时肺容量，左心室压力及其一阶导数，左心室容量，心室弹性。这些方法被扩展到神经和血流动力学变量之间的传递函数分析和时频分析（小波变换）。利用多个正弦波合成的仿真研究证实了这些方法的可行性。在本研究的第二个项目中，我们将这些系统分析应用于临床环境。(1)交感神经活动的低频成分：在肌交感神经活动的低频成分中，0.1Hz波与心率、血压呈高度平方相关，表明心率、血压与肌交感神经活动的低频成分关系密切。(2)心肺调节的传递函数分析：随机加宽的呼吸频率用于表征呼吸和左心室峰值压力之间的复杂联系。在0.05 ~ 0.15Hz频率范围内，由呼吸引起的舒张末期容积的变化对左室压力的波动起主导作用，而在0.15Hz以上，胸内压的变化直接影响左室压力的呼吸波动。(3)急性冠状动脉闭塞时交感神经活动增强：时频分析显示，心绞痛患者在球囊成形术中，急性冠状动脉闭塞引起心肌缺血时，心率和左心室峰压波动。在0.1 Hz附近的血流动力学振荡表明通过心肌缺血介导的交感神经驱动增强。这些分析将为慢性心力衰竭时自主神经系统对心血管的动态调节提供新的视角。

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.