Fresiello Libera, Rademakers Frank, Claus Piet, Ferrari Gianfranco, Di Molfetta Arianna, Meyns Bart
KU Leuven, Department of Cardiac Surgery, Leuven, Belgium.
Institute of Clinical Physiology, National Research Council, Pisa, Italy.
PLoS One. 2017 Jul 24;12(7):e0181879. doi: 10.1371/journal.pone.0181879. eCollection 2017.
Patients with a Ventricular Assist Device (VAD) are hemodynamically stable but show an impaired exercise capacity. Aim of this work is to identify and to describe the limiting factors of exercise physiology with a VAD. We searched for data concerning exercise in heart failure condition and after VAD implantation from the literature. Data were analyzed by using a cardiorespiratory simulator that worked as a collector of inputs coming from different papers. As a preliminary step the simulator was used to reproduce the evolution of hemodynamics from rest to peak exercise (ergometer cycling) in heart failure condition. Results evidence an increase of cardiac output of +2.8 l/min and a heart rate increase to 67% of the expected value. Then, we simulated the effect of a continuous-flow VAD at both rest and exercise. Total cardiac output increases of +3.0 l/min (+0.9 l/min due to the VAD and +2.1 l/min to the native ventricle). Since the left ventricle works in a non-linear portion of the diastolic stiffness line, we observed a consistent increase of pulmonary capillary wedge pressure (from 14 to 20 mmHg) for a relatively small increase of end-diastolic volume (from 182 to 189 cm3). We finally increased VAD speed during exercise to the maximum possible value and we observed a reduction of wedge pressure (-4.5 mmHg), a slight improvement of cardiac output (8.0 l/min) and a complete unloading of the native ventricle. The VAD can assure a proper hemodynamics at rest, but provides an insufficient unloading of the left ventricle and does not prevent wedge pressure from rising during exercise. Neither the VAD provides major benefits during exercise in terms of total cardiac output, which increases to a similar extend to an unassisted heart failure condition. VAD speed modulation can contribute to better unload the ventricle but the maximal flow reachable with the current devices is below the cardiac output observed in a healthy heart.
植入心室辅助装置（VAD）的患者血流动力学稳定，但运动能力受损。本研究旨在识别并描述VAD对运动生理学的限制因素。我们从文献中搜索了有关心力衰竭状态下及VAD植入后运动的数据。使用心肺模拟器对数据进行分析，该模拟器充当来自不同论文输入数据的收集器。作为初步步骤，该模拟器用于再现心力衰竭状态下从静息到运动峰值（测力计骑行）时的血流动力学演变。结果显示心输出量增加了2.8升/分钟，心率增加到预期值的67%。然后，我们模拟了连续流VAD在静息和运动时的效果。总心输出量增加了3.0升/分钟（其中0.9升/分钟归因于VAD，2.1升/分钟归因于天然心室）。由于左心室在舒张期硬度曲线的非线性部分工作，我们观察到肺毛细血管楔压有持续增加（从14 mmHg增加到20 mmHg），而舒张末期容积仅有相对较小的增加（从182 cm³增加到189 cm³）。我们最终在运动期间将VAD速度增加到最大可能值，观察到楔压降低（-4.5 mmHg），心输出量略有改善（8.0升/分钟），天然心室完全卸载。VAD可在静息时确保适当的血流动力学，但对左心室的卸载不足，且不能防止运动期间楔压升高。就总心输出量而言，VAD在运动期间也未带来显著益处，其增加程度与未辅助的心力衰竭状态相似。VAD速度调节有助于更好地卸载心室，但当前装置可达到的最大流量低于健康心脏中观察到的心输出量。
