Wei Chia-Ling, Valvano Jonathan W, Feldman Marc D, Nahrendorf Matthias, Peshock Ronald, Pearce John A
Department of Electrical Engineering, National Cheng Kung University, No. 1 University Road, Tainan 70101, Taiwan.
IEEE Trans Biomed Eng. 2007 Aug;54(8):1480-9. doi: 10.1109/TBME.2007.890732.
In order for the conductance catheter system to accurately measure instantaneous cardiac blood volume, it is necessary to determine and remove the contribution from parallel myocardial tissue. In previous studies, the myocardium has been treated as either purely resistive or purely capacitive when developing methods to estimate the myocardial contribution. We propose that both the capacitive and the resistive properties of the myocardium are substantial, and neither should be ignored. Hence, the measured result should be labeled admittance rather than conductance. We have measured the admittance (magnitude and phase angle) of the left ventricle in the mouse, and have shown that it is measurable and increases with frequency. Further, this more accurate technique suggests that the myocardial contribution to measured admittance varies between end-systole and end-diastole, contrary to previous literature. We have tested these hypotheses both with numerical finite-element models for a mouse left ventricle constructed from magnetic resonance imaging images, and with in vivo admittance measurements in the murine left ventricle. Finally, we propose a new method to determine the instantaneous myocardial contribution to the measured left ventricular admittance that does not require saline injection or other intervention to calibrate.
为了使电导导管系统能够准确测量瞬时心输出量，有必要确定并去除平行心肌组织的贡献。在以往的研究中，在开发估计心肌贡献的方法时，心肌要么被视为纯电阻性的，要么被视为纯电容性的。我们认为，心肌的电容性和电阻性特性都很显著，两者都不应被忽视。因此，测量结果应标记为导纳而非电导。我们已经测量了小鼠左心室的导纳（幅度和相位角），并表明它是可测量的且随频率增加。此外，这种更精确的技术表明，与先前的文献相反，心肌对测量导纳的贡献在收缩末期和舒张末期之间有所不同。我们已经使用从磁共振成像图像构建的小鼠左心室数值有限元模型以及小鼠左心室的体内导纳测量来检验这些假设。最后，我们提出了一种新方法来确定心肌对测量的左心室导纳的瞬时贡献，该方法不需要注射盐水或其他干预来进行校准。
