Cardiovascular Biophysics Laboratory, School of Medicine, Department of Physics, College of Arts and Sciences, Washington University Medical Center, 660 S. Euclid Ave., Box 8086, St. Louis, MO. 63110, USA.
Am J Physiol Heart Circ Physiol. 2011 Feb;300(2):H514-21. doi: 10.1152/ajpheart.00814.2010. Epub 2010 Nov 12.
Pressure-volume (P-V) loop-based analysis facilitates thermodynamic assessment of left ventricular function in terms of work and energy. Typically these quantities are calculated for a cardiac cycle using the entire P-V loop, although thermodynamic analysis may be applied to a selected phase of the cardiac cycle, specifically, diastole. Diastolic function is routinely quantified by analysis of transmitral Doppler E-wave contours. The first law of thermodynamics requires that energy (ε) computed from the Doppler E-wave (εE-wave) and the same portion of the P-V loop (εP-V E-wave) be equivalent. These energies have not been previously derived nor have their predicted equivalence been experimentally validated. To test the hypothesis that εP-V E-wave and εE-wave are equivalent, we used a validated kinematic model of filling to derive εE-wave in terms of chamber stiffness, relaxation/viscoelasticity, and load. For validation, simultaneous (conductance catheter) P-V and echocadiographic data from 12 subjects (205 total cardiac cycles) having a range of diastolic function were analyzed. For each E-wave, εE-wave was compared with εP-V E-wave calculated from simultaneous P-V data. Linear regression yielded the following: εP-V E-wave=αεE-wave+b (R2=0.67), where α=0.95 and b=6e(-5). We conclude that E-wave-derived energy for suction-initiated early rapid filling εE-wave, quantitated via kinematic modeling, is equivalent to invasive P-V-defined filling energy. Hence, the thermodynamics of diastole via εE-wave generate a novel mechanism-based index of diastolic function suitable for in vivo phenotypic characterization.
基于压力-容积（P-V）环的分析有助于从做功和能量的角度评估左心室功能的热力学。通常情况下，这些量是通过整个 P-V 环在一个心动周期内计算的，尽管热力学分析也可以应用于心动周期的特定阶段，特别是舒张期。舒张功能通常通过分析二尖瓣多普勒 E 波轮廓来定量评估。热力学第一定律要求从多普勒 E 波（εE-波）和 P-V 环的同一部分（εP-V E-波）计算得出的能量（ε）相等。这些能量以前没有被推导出来，也没有通过实验验证它们的预测等效性。为了验证假设即 εP-V E-波和 εE-波是等效的，我们使用了一个经过验证的充盈运动学模型，根据腔室硬度、松弛/粘弹性和负荷来推导 εE-波。为了验证，我们对 12 名患者（共 205 个心动周期）同时进行了（电导导管）P-V 和超声心动图数据的分析，这些患者的舒张功能具有不同的范围。对于每个 E 波，我们将 εE-波与从同时的 P-V 数据计算得出的 εP-V E-波进行比较。线性回归得到以下结果：εP-V E-波=αεE-波+b（R2=0.67），其中α=0.95，b=6e(-5)。我们得出结论，通过运动学建模定量评估的抽吸引发的早期快速充盈的 E 波衍生能量 εE-波与侵入性 P-V 定义的充盈能量相等。因此，通过 εE-波产生的舒张期热力学提供了一种基于机制的新颖的舒张功能指数，适用于体内表型特征描述。
