Primary Study On Relation Between Myocardial Elasticity And Cardiac Reserve

Myocardial contractility is the fundamental ability of the heart muscle. It is very necessary to get comprehensive and objective assessments of its function, which include not only evaluating the level of myocardial contractility in one state but also evaluating contractility reserve. A great amount of animal and human experiments show that maximum systolic myocardial stiffness is a exclusive and sensitive index to evaluate myocardial contractility, for its independence on preload, afterload and ventricular geometry, insensitivity to variety in heart rate. Though myocardial stiffness is a sensitive index to evaluate myocardial contractility, it cannot be used to evaluate myocardial contractility reserve, which stands for the extent of heart failure. Combining myocardial stiffness index with contractility reserve to study the relation between them, the thesis proposes the concept of myocardial stiffness reserve and its clinical noinvasive detection method, which reflects myocardial contractility reserve in cardiac function. Currently, difficulty of myocardial stiffness in clinical application has led a limited use of this concept. The improvement of its detection method is needed. The thesis examined methods of exercise experiment and introduced static exercise to change the load of cardiac stroke instead of invasive operation or administration. Static exercise increases blood pressure and heart rate, but it may change myocardial contractility. To examine its effects, 21 undergraduates are subjected to static exercise experiment. The results show that static exercise lifts blood pressure up obviously but does not change myocardial contractility, which meet the demand of changing the load of cardiac stroke in the detection of myocardial stiffness. Based on the improvement of the detection method of myocardial stiffness, the clinical noinvasive detection method of stiffness reserve is proposed. The detailed clinical procedure is drawn out to support the validation of myocardial stiffness reserve concept. Myocardial stiffness reserve is a potent, comprehensive and objective index to evaluate the function of myocardial contractility and may be helpful to diagnose early heart failure.