Admittance to measure cardiac mechanics in mice

描述（由申请人提供）：遗传改变小鼠提供了一种机制来定义个体基因的体内表型。这与涉及产生导致充血性心力衰竭的心肌疾病的基因特别相关。在大型动物中评估血流动力学表型的经典方法是通过左心室（LV）压力-容积（PV）分析。然而，确定小鼠LV中的绝对和瞬时体积一直受到其小尺寸和快速心率的困扰。电导测量通过产生与任何心肌大小或心率兼容的瞬时LV体积信号，为该问题提供了有吸引力的解决方案。不幸的是，第一代电导仪器即使在单个较低频率下也生成由血液和心肌组成的瞬时电导（体积）信号。仅需要血液成分进行PV分析。提出了一种通过测量导纳（复电导）来克服这种限制的机制。导纳由左室血液电导和心肌电导的大小以及心肌电导的相位角组成。传统的单频电导仅测量包括血液和心肌成分的电导信号的幅度。由于可测量的相位角是肌肉独有的，导纳提供了一种更好的方法来确定和消除瞬时心肌对组合LV电导（体积）信号的贡献。本授权申请的目标是开发、校准和验证一种仪器，以真实的时间测量导纳信号的幅度和相位角。为了实现这一目标，我们将- 1）开发模拟硬件和数字数据采集导纳仪器，2）开发一种更准确的方法，使用FEM从导纳测量中获得LV体积，3）证明导纳仪器上级传统的单频MRI。

DESCRIPTION (provided by applicant): Genetically altered mice provide a mechanism to define the in vivo phenotype of individual genes. This is especially relevant to genes implicated in producing myocardial diseases leading to congestive heart failure. The classic method to assess the hemodynamic phenotype in larger animals is through left ventricular (LV) pressure-volume (PV) analysis. However, determining absolute and instantaneous volume in the murine LV has been plagued by its small size and rapid heart rate. Conductance measurements offer an attractive solution to this problem by generating an instantaneous LV volume signal compatible with any myocardial size or heart rate. Unfortunately, the first generation conductance instrument generates an instantaneous conductance (volume) signal composed of blood and myocardium even at a single lower frequency. Only the blood component is desired for PV analysis. A mechanism to overcome this limitation is proposed by measuring admittance (complex conductance). Admittance is composed of both the magnitude of LV blood and myocardial conductance, and the phase angle of myocardial conductance. Traditional single frequency conductance measures only the magnitude of the conductance signal, which includes both the blood and myocardial components. Because measurable phase angle is unique to muscle, admittance offers a better method to determine and remove the instantaneous myocardial contribution to the combined LV conductance (volume) signal. The GOAL of this grant application is to develop, calibrate, and validate an INSTRUMENT to measure both the magnitude and the phase angle of the admittance signal in real time. To accomplish this goal, we will - 1) Develop both analog hardware and digital data acquisition Admittance Instruments, 2) Develop a more accurate method to derive LV volume from admittance measurements using FEM, and 3) Demonstrate that an Admittance Instrument is superior to traditional single frequency with MRI.