Kuo Alexander S, Sato Hitoshi, Reoma Junewai L, Cook Keith E
Department of Surgery, University of Michigan, B560B MSRBII, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109, USA.
Cardiovasc Eng. 2009 Dec;9(4):153-60. doi: 10.1007/s10558-009-9083-2.
Right ventricular (RV) afterload is a key determinant of RV function and is increased in many cardiopulmonary pathologies. Pulmonary circulation input impedance has been used to quantify afterload previously but due to its complexity has not been widely applied. This study examines the effect of a subset of the impedance spectrum, the zeroth and first harmonic impedance moduli (Z (0), Z (1)), on RV performance in large animals. An artificial circuit with adjustable resistance and compliance (C) was implanted into the pulmonary circulation of five sheep. Resistance was varied to increase Z (0) in increments of 2 mmHg/(L/min) until Z (0) was 8 mmHg/(L/min) above baseline. At each Z (0), C was adjusted between 0, 0.5 and 2 mL/mmHg or 0, 1, and 5 mL/mmHg. Fourier transforms of the pulmonary artery pressure and flow in each situation were used to calculate the pulmonary impedance. Results show that the percent change in cardiac output (%DeltaCO) is linearly related to the change in Z (0) (DeltaZ (0)). Increases in Z (1) (DeltaZ (1)) decreased %DeltaCO but to a much smaller degree, with the effect of DeltaZ (1) increasing with DeltaZ (0). Regression of these results produce the equation: %DeltaCO = (-0.0829DeltaZ (1) - 3.65)DeltaZ (0) - 9.02 (R (2) = 0.69). Blood flow and pressure moduli are small at harmonics higher than the first and are unlikely to affect RV function. Therefore, during acute, high afterload states, Z (0) is the primary determinant of CO, while the effect of Z (1) is minor.
右心室（RV）后负荷是右心室功能的关键决定因素，在许多心肺疾病中都会增加。肺循环输入阻抗此前已被用于量化后负荷，但由于其复杂性尚未得到广泛应用。本研究考察了阻抗谱的一个子集，即零阶和一阶谐波阻抗模量（Z(0)、Z(1)）对大型动物右心室性能的影响。将一个具有可调电阻和顺应性（C）的人工回路植入五只绵羊的肺循环中。改变电阻以2 mmHg/（L/min）的增量增加Z(0)，直到Z(0)比基线高8 mmHg/（L/min）。在每个Z(0)时，将C调整为0、0.5和2 mL/mmHg或0、1和5 mL/mmHg。利用每种情况下肺动脉压力和流量的傅里叶变换来计算肺阻抗。结果表明，心输出量的百分比变化（%ΔCO）与Z(0)的变化（ΔZ(0)）呈线性相关。Z(1)的增加（ΔZ(1)）使%ΔCO降低，但程度要小得多，且ΔZ(1)的影响随ΔZ(0)的增加而增大。对这些结果进行回归得到方程：%ΔCO = （-0.0829ΔZ(1) - 3.65）ΔZ(0) - 9.02（R(2) = 0.69）。高于一阶的谐波处的血流和压力模量较小，不太可能影响右心室功能。因此，在急性高后负荷状态下，Z(0)是心输出量的主要决定因素，而Z(1)的影响较小。
