Swine C
Service de Gériatrie, Cliniques Universitaires UCL de Mont-Godinne, Yvoir, Belgique.
Presse Med. 1992 Jul 22;21(26):1216-21.
In normal subjects at rest neither heart rate nor ejection volume are influenced by age. The loss of elasticity of the great arteries, and in particular the aorta which becomes tortuous and wider, results in an increase of impedance at ejection. At systole time pressure rises in the whole cardiovascular system, so that the left ventricle is subjected to an increase of parietal tension to which it adapts itself by hypertrophy which normalizes this tension. Ejection fraction and end-systolic volume are thus preserved, and the systolic function at rest globally remains unmodified by age. The delay and slowing down of relaxation due to hypertrophy of the left ventricle, to the reflection waves and to other changes in cardiac muscle physical properties during senescence reduce the importance of the initial phase of left ventricular filling. This major modification of diastolic dynamics at rest is compensated, at the end of diastole, by a more vigorous contraction of the left atrium, which increases its contribution to left ventricular filling. The global filling volume is thus preserved and the end-diastolic volume remains appropriate, these two conditions being necessary to start off a normal ejection. In normal subjects at exercise the cardiac function is also modified by age. Maximum heart rate is reduced in the elderly, whereas the ejection volume increases more than in younger subjects, which maintains the appropriate cardiac output. This adaptation takes place owing to an increase of cardiac volume and through Starling's mechanism which ensures a greater ejection volume. Only the maximum exercise level (VO2 max) decreases with age, mainly because of the decrease of skeletal muscle mass. Filling of the left ventricle seems to continue to rely, at rest as at exercise, on atrial compensation. Cardiac output therefore is globally maintained with age during a dynamic effort. During isometric exercise, which in the elderly results in a higher rise in blood pressure, the ejection fraction decreases, the end-systolic volume increases and the initial filling decreases but is compensated by a greater contribution of the atrium. Thus, cardiac work at rest and during exercise is well preserved in the ageing man, due to secondary homeostatic adaptations which counterbalance the primary age-related changes. The principal primary changes are loss of elasticity of the great vessels and reduction of efficacy in response to adrenergic stimulation. The principal secondary adaptations are left ventricular hypertrophy, increased atrial contribution and, during exercise, intervention of Starling's mechanism.
在静息状态下，正常受试者的心率和射血容积均不受年龄影响。大动脉弹性丧失，尤其是主动脉变得迂曲且增宽，导致射血时阻抗增加。在收缩期，整个心血管系统压力升高，使得左心室壁张力增加，左心室通过肥厚进行适应，从而使这种张力恢复正常。射血分数和收缩末期容积得以保留，静息时的收缩功能总体上不因年龄而改变。由于左心室肥厚、反射波以及衰老过程中心肌物理特性的其他变化导致舒张延迟和减慢，这降低了左心室充盈初始阶段的重要性。静息时舒张动力学的这一主要改变在舒张末期通过左心房更有力的收缩得到代偿，左心房对左心室充盈的贡献增加。因此，总体充盈量得以保留，舒张末期容积保持合适，这两个条件对于开始正常射血是必要的。在运动状态下，正常受试者的心脏功能也会因年龄而改变。老年人的最大心率降低，而射血容积增加幅度大于年轻受试者，从而维持适当的心输出量。这种适应是由于心脏容积增加以及通过确保更大射血容积的Starling机制实现的。仅最大运动水平（最大摄氧量）随年龄下降，主要原因是骨骼肌质量减少。左心室的充盈在静息和运动时似乎都继续依赖心房代偿。因此，在动态运动期间，心输出量总体上随年龄保持稳定。在等长运动中，老年人血压升高幅度更大，射血分数降低，收缩末期容积增加，初始充盈减少，但可通过心房更大的贡献得到代偿。因此，由于继发性稳态适应抵消了与年龄相关的原发性变化，老年男性静息和运动时的心脏作功得以良好维持。主要的原发性变化是大血管弹性丧失以及对肾上腺素能刺激的反应效能降低。主要的继发性适应是左心室肥厚、心房贡献增加以及运动时Starling机制的介入。
