Department of Bioengineering, University of Louisville, Kentucky 40202, USA.
ASAIO J. 2012 Jul-Aug;58(4):353-62. doi: 10.1097/MAT.0b013e318256bb50.
Ventricular assist devices (VADs) have been used successfully as a bridge to transplant in heart failure patients by unloading ventricular volume and restoring the circulation. An artificial vasculature device (AVD) is being developed that may better facilitate myocardial recovery than VAD by controlling the afterload experienced by the native heart and controlling the pulsatile energy entering into the arterial system from the device, potentially reconditioning the arterial system properties. The AVD is a valveless, 80 ml blood chamber with a servo-controlled pusher plate connected to the ascending aorta by a vascular graft. Control algorithms for the AVD were developed to maintain any user-defined systemic input impedance (IM) including resistance, elastance, and inertial components. Computer simulation and mock circulation models of the cardiovascular system were used to test the efficacy of two control strategies for the AVD: 1) average impedance position control (AIPC)-to maintain an average value of resistance during left ventricular (LV) systole and 2) instantaneous impedance force feedback (IIFF) and position control (IIPC)-to maintain a desired value or profile of resistance and compliance. Computer simulations and mock loop tests were performed to predict resulting cardiovascular pressures, volumes, flows, and the resistance and compliance experienced by the native LV during ejection for simulated normal, failing, and recovering LV. These results indicate that the LV volume and pressure decreased, and the LV stroke volume increased with decreasing IM, resulting in an increased ejection fraction. Although the AIPC algorithm is more stable and can tolerate higher levels of sensor errors and noise, the IIFF and IIPC control algorithms are better suited to maintain any instantaneous IM or an IM profile. The developed AVD impedance control algorithms may be implemented with current VADs to promote myocardial recovery and facilitate weaning.
心室辅助装置（VAD）已成功用作心力衰竭患者移植的桥接方法，通过减轻心室容积和恢复循环。正在开发一种人工血管装置（AVD），它通过控制原生心脏所经历的后负荷并控制设备进入动脉系统的脉动能量，从而更好地促进心肌恢复，可能重塑动脉系统特性。AVD 是一个无阀、80 毫升血液腔室，带有一个由伺服控制的推板，通过血管移植物与升主动脉相连。为 AVD 开发了控制算法，以维持任何用户定义的系统输入阻抗（IM），包括阻力、弹性和惯性分量。使用心血管系统的计算机模拟和模拟循环模型来测试 AVD 的两种控制策略的效果：1）平均阻抗位置控制（AIPC）-在左心室（LV）收缩期间维持阻力的平均值，2）瞬时阻抗力反馈（IIFF）和位置控制（IIPC）-维持期望的阻力和顺应性值或轮廓。进行了计算机模拟和模拟循环测试，以预测模拟正常、衰竭和恢复的 LV 时，原生 LV 在射血期间经历的心血管压力、体积、流量以及阻力和顺应性。这些结果表明，LV 体积和压力随着 IM 的降低而降低，LV 每搏量随着 IM 的降低而增加，导致射血分数增加。虽然 AIPC 算法更稳定，并且可以容忍更高水平的传感器误差和噪声，但 IIFF 和 IIPC 控制算法更适合维持任何瞬时 IM 或 IM 轮廓。开发的 AVD 阻抗控制算法可以与当前的 VAD 一起实施，以促进心肌恢复和促进脱机。
