后负荷对左室射血力的影响

Influence of afterload on left ventricular ejection force

为了探讨Ｉｓａａｚ等根据牛顿第二定律测定的左空射血力是否与后负荷有关，我们将３５例受试者分为正常组（２０例）和高血压病组（１５例）．用彩色多普勒超声心动图测取主动脉瓣前向血流的平均加速度（ＭＡ），加速时间内的速度时间积分（ＶＴＩ）和主动脉瓣口面积（ＣＳＡ），则左室射血力（ＬＶＥＦ）＝ρ×ＣＳＡ×ＶＴＩ×ＭＡ，其中ρ为血液密度（１．０６ｇ／ｃｍ３），ρ×ＣＳＡ×ＶＴＩ为加这时间内的射血质量。分别将ＭＡ，ＶＴＩ和ＬＶＥＦ与收缩压（ＳＰ）进行相关分析，结果ＭＡ，ＶＴＩ和ＬＶＥＦ与ＳＰ呈显著负相关，（ｒ分别为－０．７８，－０．７０和－０．６７．Ｐ＜０．０１）．高血压病组的ＭＡ，ＶＴＩ和ＬＶＥＦ均显著低于正常组，说明Ｉｓａａｚ等提出的在室射血力考虑到了加速度和质量的概念，是一项更为合理的方法，但是明显受后负荷影响，并且高血压病组的ＬＶＥＦ低于正常组，提示后负荷越重，左空射血力越低，所以使用该方法时应考虑到后负荷的作用。

In order to explore whether left ventricular ejection force(LVEF) determined by Isaazet al was afterload-dependent,we tested 20 normal subjects(normal group)and 15 hypertensive patients(hypertensive group).A correlation analysis was made between aortic mean acceleration(MA),velocity-time integral(VTI),and LVEF measured by Doppler on the one hand and systolic blood pressure on the other hand.The results showed that MA,VTI and LVEF had good negative correlationwith systolic blood pressure(r=-0.78,-0.70 and-0.67,P<0.01)and that MA,VTI andLVEF were larger in the normal group than in the hypertensive group.These results suggested thatLVEF determined by Isaaz et al was afterload-dependent.The influence of afterload should be considered when the index LVEF was used.