Admittance to measure cardiac mechanics in mice

描述(由申请人提供)：转基因小鼠提供了一种机制来定义单个基因的体内表型。这与导致心肌疾病导致充血性心力衰竭的基因尤其相关。评估大型动物血流动力学表型的经典方法是通过左心室(LV)压力-容量(PV)分析。然而，测定小鼠左心室的绝对和瞬时容量一直受到其体积小和心率快的困扰。电导测量通过产生与任何心肌大小或心率兼容的瞬时LV容量信号，为这一问题提供了一个有吸引力的解决方案。不幸的是，第一代电导仪即使在单一较低的频率下也会产生由血液和心肌组成的瞬时电导(体积)信号。PV分析只需要血液成分。提出了一种通过测量导纳(复电导)来克服这一限制的机制。导纳由左室血和心肌电导的大小以及心肌电导的相位角组成。传统的单频电导只测量电导信号的大小，包括血液和心肌成分。由于可测量的相角是肌肉独有的，导纳提供了一种更好的方法来确定和消除瞬时心肌对合并的LV电导(体积)信号的贡献。这项授权申请的目标是开发、校准和验证一种仪器，以实时测量导纳信号的幅度和相角。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)开发一种更精确的方法，使用有限元方法从导纳测量中求出左心室体积，以及3)利用磁共振技术证明导纳仪器优于传统的单频。

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.