人类左心室的能量转换效率。

Energy conversion efficiency in human left ventricle.

作者信息

Kameyama T, Asanoi H, Ishizaka S, Yamanishi K, Fujita M, Sasayama S

机构信息

Second Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Japan.

出版信息

Circulation. 1992 Mar;85(3):988-96. doi: 10.1161/01.cir.85.3.988.

DOI:10.1161/01.cir.85.3.988

PMID:1537135

Abstract

BACKGROUND

Left ventricular mechanical efficiency is one of the most important measures of left ventricular pump performance. Several clinical studies, however, have shown that mechanical efficiency does not fall substantially as the heart fails. To clarify the insensitivity of mechanical efficiency to the change in pump performance, we analyzed human left ventricular mechanical efficiency, applying the concept of left ventricular systolic pressure-volume area (PVA).

METHODS AND RESULTS

PVA correlates linearly with myocardial oxygen consumption per beat (MVO2): MVO2 = a.PVA+b, and represents the total mechanical energy of contraction. We determined MVO2-PVA relation and external work in 11 patients with different contractile states. We also calculated the energy transfer from MVO2 to PVA (PVA/MVO2 efficiency), that from PVA to external work (work efficiency), and mechanical efficiency (external work/MVO2). Left ventricular pressure-volume loops were constructed by plotting the instantaneous left ventricular pressure against the left ventricular volume at baseline and during pressure loading. The contractile properties of the ventricle were defined by the slope of the end-systolic pressure-volume relation (Ees). Pressure elevation raised external work by 41.4%, PVA by 71.2%, and MVO2 by 54.5%. These changes were associated with a decrease in work efficiency and an increase in PVA/MVO2 efficiency. The opposite directional changes in these two efficiencies rendered the mechanical efficiency constant. The slope, a, of the relation between MVO2 and PVA was relatively constant (2.46 +/- 0.33) over the range of 0.8-8.8 mm Hg/ml of Ees, but the oxygen axis intercept, b, tended to decrease with the reduction in Ees. PVA/MVO2 efficiency correlated inversely (r = -0.66, p less than 0.05) with Ees, whereas work efficiency correlated linearly with Ees (r = 0.91, p less than 0.01).

CONCLUSIONS

Mechanical efficiency is not appreciably affected by changes in loading and inotropic conditions as long as the left ventricular contractility is not severely depressed.

摘要

背景

左心室机械效率是左心室泵功能最重要的指标之一。然而，多项临床研究表明，随着心脏功能衰竭，机械效率并未显著下降。为阐明机械效率对泵功能变化的不敏感性，我们应用左心室收缩压-容积面积（PVA）的概念分析了人类左心室机械效率。

方法与结果

PVA与每搏心肌耗氧量（MVO2）呈线性相关：MVO2 = a·PVA + b，代表收缩的总机械能。我们测定了11例不同收缩状态患者的MVO2 - PVA关系及外部功。我们还计算了从MVO2到PVA的能量转移（PVA/MVO2效率）、从PVA到外部功的能量转移（功效率）以及机械效率（外部功/MVO2）。通过绘制基线及压力负荷时瞬时左心室压力与左心室容积的关系构建左心室压力-容积环。心室的收缩特性由收缩末期压力-容积关系（Ees）的斜率定义。压力升高使外部功增加41.4%，PVA增加71.2%，MVO2增加54.5%。这些变化与功效率降低及PVA/MVO2效率增加相关。这两种效率的相反方向变化使机械效率保持恒定。在Ees为0.8 - 8.8 mmHg/ml的范围内，MVO2与PVA关系的斜率a相对恒定（2.46 ± 0.33），但氧轴截距b随Ees降低而趋于减小。PVA/MVO2效率与Ees呈负相关（r = -0.66，p < 0.05），而功效率与Ees呈线性相关（r = 0.91，p < 0.01）。