Sdougos H P, Schultz D L, Tan L B, Bergel D H, Rajagopalan B, Lee G de J
Circ Res. 1982 Jan;50(1):74-85. doi: 10.1161/01.res.50.1.74.
The power output of the left ventricle as measured by the product of the Fourier components of aortic pressure and aortic flow is linked by definition to the arterial impedance facing the heart as measured by the quotient of these components. Consequently, the use of power measurements to assess ventricular performance can be ambiguous when accompanied by afterload changes. The heart is considered to function normally between two extremes, a constant flow pump, and a constant constant pressure pump, and two power limits are defined from these. The power limits describe the extent to which impedance changes can affect the power delivered by the left ventricle. Measured power changes that are found to lie outside the two limits can be unambiguously ascribed to changes in inotropic state. The results from preliminary dog experiments designed to test this method are reported. Cardiac sympathetic stimulation and isoprenaline infusion were used to provide a pure inotropic stimulus and a mixture of inotropic and afterload changes, respectively. The technique was able to detect inotropic changes in the heart even in the presence of simultaneous changes in afterload. Eight conventional indices of cardiac performance were monitored for comparison. The extent of their afterload dependence may not be as easily quantified.
通过主动脉压力和主动脉血流的傅里叶分量之积来测量的左心室输出功率，根据定义与用这些分量的商来测量的心脏所面对的动脉阻抗相关。因此，当伴有后负荷变化时，使用功率测量来评估心室功能可能会产生歧义。心脏被认为在两个极端之间正常运作，即恒流泵和恒压泵，并且由此定义了两个功率极限。功率极限描述了阻抗变化能够影响左心室输送功率的程度。被发现超出这两个极限的测量到的功率变化可以明确归因于心肌收缩状态的变化。报告了旨在测试该方法的初步犬实验结果。心脏交感神经刺激和异丙肾上腺素输注分别用于提供单纯的心肌收缩刺激以及心肌收缩和后负荷变化的混合刺激。该技术即使在存在后负荷同时变化的情况下也能够检测到心脏的心肌收缩变化。为作比较监测了八个传统的心脏功能指标。它们对后负荷的依赖程度可能不那么容易量化。
