| Author/Editor | Potočnik, Nejka | |
| Title | Viskoelastične lastnosti izoliranega levega prekata budre v diastoli | |
| Type | monografija | |
| Place | Ljubljana | |
| Publisher | Medicinska fakulteta | |
| Publication year | 2000 | |
| Volume | str. 89 | |
| Language | slo | |
| Abstract | Introduction: Cardiac muscle is a soft, porous, biaxial, viscoelastic material, exhibiting stress relaxation and hysteresis after being passively stretched and released. The left ventricular pressure (pLV) changes during cyclic stepwise volume loading and unloading of the left ventricle (LV) and could be separated into a time independent, elastic and a time dependent, viscoelastic part. The viscoelastic part is affected by transient LV volume changes and by the history of previous deformations of the heart muscle tissue, respectively. It could be decomposed into the fast and the slow time decaying components with time constants of relaxation equal to 1 and 20s, respectively, revealing different mechanisms governing the viscoelastic behavior. The aim of the study: The aim of the present thesis is to quantify the elastic and viscoelastic part of pLV by assessing the universal elastic behavior and calculating the spectrum of amplitudes for the slow and fast decaying components of the viscoelastic part of the pressure. The width of pressure hysteresis loop is analyzed as a function of different volume loading procedures. The manifestation of myocardial material properties in viscoelastic behavior of epicardial segment lengths in two principal epicardial directions is investigated further. We want to determine the time independent part of both principal strains during volume loading and unloading procedure and to find out whether the epicardial segment lengths exhibit creep while LV volume is kept constant. The time dependence of creep is compared with the time course of stress relaxation. The change of eccentricity and volume, calculated from the epicardial segment lengths by the ellipsoid model, were tracked dtiting volume loading to show the LV shape changes following the loading and unloading procedure and to test whether calculated volume correlate with the injected one. (Abstract truncated at 2000 characters) | |
| Descriptors | HEART VENTRICLE VENTRICULAR PRESSURE VENTRICULAR FUNCTION, LEFT DIASTOLE GUINEA PIGS CARDIAC VOLUME ELASTICITY MYOCARDIUM |