Sjöberg B J, Eidenvall L, Loyd D, Wranne B, Ask P
Department of Clinical Physiology, Linköping University, Sweden.
Acta Physiol Scand. 1993 Mar;147(3):271-9. doi: 10.1111/j.1748-1716.1993.tb09499.x.
There is an increasing demand for non-invasive methods for the assessment of left ventricular function. Ultrasound Doppler methods are promising, and the early systolic flow velocity signal immediately distal to the aortic valve has been used clinically for this purpose. However, the signal is influenced not only by left ventricular ejection but also by systemic vascular characteristics. Their relative contribution to the time-velocity signal has not been analysed in depth previously. A theoretical analysis, based on a three-element Windkessel model, neglecting peripheral outflow in early systole and assuming linear pressure rise, was therefore tested in computer and hydraulic model simulations where peripheral outflow was included. Significant changes in early aortic flow velocity parameters were found when vascular characteristics were altered. As predicted by the theory, with a standardized aortic valve area and aortic pressure change, the simulations confirmed that maximal flow velocity is related to compliance of the aorta and the large arteries, and that maximal acceleration is inversely related to the characteristic impedance of the aorta. Therefore, maximal velocity and acceleration can be used for assessment of left ventricular function only in situations where vascular characteristics can be considered relatively constant or where they can be estimated.
对用于评估左心室功能的非侵入性方法的需求日益增加。超声多普勒方法很有前景，主动脉瓣远端的早期收缩期血流速度信号已在临床上用于此目的。然而，该信号不仅受左心室射血的影响，还受全身血管特征的影响。它们对时间-速度信号的相对贡献此前尚未进行深入分析。因此，基于三元Windkessel模型，在计算机和水力模型模拟中对忽略早期收缩期外周流出并假设压力线性上升的理论分析进行了测试，其中包括外周流出。当血管特征改变时，发现早期主动脉流速参数有显著变化。正如该理论所预测的，在标准化主动脉瓣面积和主动脉压力变化的情况下，模拟结果证实最大流速与主动脉和大动脉的顺应性有关，最大加速度与主动脉的特性阻抗成反比。因此，仅在血管特征可被视为相对恒定或可被估计的情况下，最大速度和加速度才可用于评估左心室功能。
