Study for the mechanism of mechanical alternans

机械交替是一种很难理解的现象，交替的强和弱节拍与恒定的节拍到节拍的间隔。它可能是慢性心力衰竭患者衰竭心肌和室颤之间的联系者。间隔-力关系（Interval-force relationship），即所谓的机械恢复，是心肌收缩力依赖于肌浆网（SR）Ca^（2+）循环的内在调节原理。力-频关系也被认为反映了SR的Ca^（++）处理。我们分析了慢性心力衰竭患者的间期-力关系和力-频关系。在房颤患者中，机械恢复曲线能够从左心室收缩力的逐搏方差中获得，该方差由前前耦合间期调整。我们估计机械恢复曲线拟合单指数曲线。机械恢复曲线τ值随射血分数的降低而雅阁。分析了力-频关系。在慢性心力衰竭患者中，峰值力率向较低心率移动。患者的力增益很小。力增益与左心室射血分数相关。我们能够获得足够的机械恢复曲线后，强拍和弱拍从一些患者。弱拍后的机械恢复曲线比强拍后的曲线陡升。弱拍后的时间常数比强拍后的时间常数短。因此，在机械交替过程中，强拍和弱拍后的机械恢复特性是不同的。这表明机械交替起源于心肌Ca^（2+）循环特性的交替变化。

Mechanical alternans is a poorly-understood phenomenon of alternating strong and weak beats with a constant beat-to-beat interval. It is a possible linker between failing myocardium and ventricular fibrillation in patients with chronic heart failure. Interval-force relationship, so-called mechanical restitution, is an intrinsic regulatory principle of myocardial contractility depending on sarcoplasmic reticulum (SR)Ca^(2+) cycling. Force-frequency relationship is also considered to reflect Ca^(++) handling of SR. We analyzed interval-force relationship and force frequency relationship in patients with chronic heart failure. In patients with atrial fibrillation, mechanical restitution curves were able to be obtained from beat by beat variance of left ventricular contractility adjusted by pre-preceding coupling intervals. We estimated mechanical restitution curves by fitting to monoexponential curves. Tau of the mechanical restitution curve increased in accord with the decrease of ejection fraction. We analyzed force-frequency relationship. In patients with chronic heart failure, peak force rate shifted to lower heart rate. The force gain of patients was little. A force gain was correlated to the left ventricular ejection fraction. We were able to obtain adequate mechanical restitution curves after both strong beats and weak beats from some patients. Mechanical restitution curves after weak beats steeply rose compared with those after strong beats. The time constant after weak beats were shorter than those after strong beats. Thus mechanical restitution properties were different after strong beats and weak beats during mechanical alternans. This implies that mechanical alternans originates from alternating changes of myocardial Ca^(2+) cycling property.