Slinker B K, Glantz S A
Cardiovascular Research Institute, University of California, San Francisco 94143.
Am J Physiol. 1989 Apr;256(4 Pt 2):R962-75. doi: 10.1152/ajpregu.1989.256.4.R962.
A variety of regulatory mechanisms have evolved to control the heart's pump function because the cardiovascular system must continually adapt to the changing demands that body functions place on it. This regulation takes place through many physiological systems; however, fine adjustments in cardiac pumping probably require adaptations more quickly than external control mechanisms (such as the autonomic nervous system) can compensate. Thus cardiac pumping is also regulated by mechanisms intrinsic to the heart. To better understand these intrinsic control mechanisms, we studied the beat-to-beat response of left ventricular function to continually varying changes in loading conditions produced by transiently occluding the pulmonary artery, venae cavae, and aorta. We used multiple linear regression to identify and quantify the important beat-to-beat determinants of left ventricular systolic function, quantified as stroke work. We could not adequately explain or predict beat-to-beat changes in stroke work with traditional determinants of ventricular function, preload, afterload, and heart rate, because a large systematic error remains after taking these traditional determinants of function into account. To eliminate this systematic error, we had to include some function of previous beat stroke volume and end-systolic size and pressure. This additional information significantly improved both our ability to model the observed transient changes in left ventricular stroke work and to predict additional observations that were not used to develop our model. We conclude that previous beat contraction history is an important determinant of left ventricular function and implies an important regulatory mechanism whereby the left ventricle can fine tune its function from beat to beat in response to continually changing loading conditions.
由于心血管系统必须不断适应身体功能对其提出的不断变化的需求，因此已经进化出多种调节机制来控制心脏的泵血功能。这种调节通过许多生理系统进行；然而，心脏泵血的精细调节可能需要比外部控制机制（如自主神经系统）能够补偿的速度更快的适应。因此，心脏泵血也受心脏内在机制的调节。为了更好地理解这些内在控制机制，我们研究了左心室功能对肺动脉、腔静脉和主动脉短暂闭塞所产生的负荷条件持续变化的逐搏反应。我们使用多元线性回归来识别和量化左心室收缩功能的重要逐搏决定因素，以每搏功来量化。我们无法用传统的心室功能决定因素（前负荷、后负荷和心率）充分解释或预测每搏功的逐搏变化，因为在考虑这些传统的功能决定因素后仍存在较大的系统误差。为了消除这种系统误差，我们必须纳入前搏每搏量以及收缩末期大小和压力的一些函数。这些额外信息显著提高了我们模拟观察到的左心室每搏功瞬态变化的能力，以及预测未用于建立我们模型的其他观察结果的能力。我们得出结论，前搏收缩历史是左心室功能的一个重要决定因素，这意味着存在一种重要的调节机制，通过该机制左心室可以根据不断变化的负荷条件逐搏微调其功能。
