抄録
Echocardiography combined with simultaneous measurement of peak systemic pressure was applied for analysis of left ventricular function within a two-dimensional framework which took into account the preload, the afterload and the level of myocardial inotropic state. This approach is particulary useful for understanding the behavior of the normal and diseased ventricle under various abnormal loading conditions where a single measurement of ejection characteristics does not necessarily reflect inotropic state. The pressure (or wall stress) - diameter loops were constructed during systolic pressure change and diameter at the end of ejection was linearly related to systolic pressure or systolic wall stress. This relation generally approximates the isovolumic length- tension relation which is independent of initial length and unique to a given level of inotropic state. The echocardiographically determined shortening velocity of the ventricular wall (mean Vcf) is inversely related to the level of afterload, if the preload is fixed. However, the normal human ventricle exhibits only minor changes in Vcf in response to a moderate acute pressure stress, as modified by the preload (Frank-Starling) reserve. If the limit of preload reserve is reached, Vcf will diminish ; that is, a mismatch between afterload and the level of inotropic state occurs. The echocardiographic approach for the assessment of cardiac performance thus allows an early detection of impairment of ventricular function and offers a possible explanation of how the ventricle operates on a descending limb of function and of how the ventricle adapts to chronic mechanical overload.
