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

在这项研究的第一个项目中，我们开发了交感神经活动、心率、瞬时肺容量、左室压及其一阶导数、左室容量和左室弹性的频谱成分的同步分析。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)。通过对多个正弦波合成的仿真研究，验证了这些方法的可行性。在这项研究的第二个项目中，我们将这些系统分析应用到临床环境中。(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，0.1赫兹的波与心率和血压呈高度平方相关，表明这些变量之间存在密切的关系。(2)心肺调节传递函数分析：用随机加宽呼吸频率表征呼吸与左心室峰压之间的复杂联系。在0.05~0.15赫兹频率范围内，舒张末容量随呼吸的变化在压力变化中起主导作用，而在0.15赫兹以上，胸腔内压的变化直接导致左心室压力的呼吸波动。(3)急性冠脉闭塞时交感神经活动增强：时频分析显示，心绞痛患者球囊成形术中，急性冠脉闭塞引起心肌缺血时，心率和左室峰压波动。0.1Hz处的血流动力学振荡提示心肌缺血引起的交感神经冲动增强。这些分析将为研究慢性心力衰竭患者自主神经系统的心血管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.