Determination of myocardial energetic output for cardiac rhythm pacing

This research is aimed to the determination of the changes in the cardiac energetic output for three different modes of cardiac rhythm pacing. The clinical investigation of thirteen patients with the permanent dual-chamber pacemaker implantation was carried out. The patients were taken to echocardiography examination conducted by way of three pacing modes (AAI, VVI and DDD). The myocardial energetic parameters—the stroke work index (SWI) and the myocardial oxygen consumption (MVO2) are not directly measurable, however, their values can be determined using the numerical model of the human cardiovascular system. The 24-segment hemodynamical model (pulsating type) of the human cardiovascular system was used for the numerical simulation of the changes of myocardial workload for cardiac rhythm pacing. The model was fitted by well-measurable parameters for each patient. The calculated parameters were compared using the two-tailed Student’s test. The differences of SWI and MVO2 between the modes AAI and VVI and the modes DDD and VVI are statistically significant (P < 0.05). On the other hand, the hemodynamic effects for the stimulation modes DDD and AAI are almost identical, i.e. the differences are statistically insignificant (P > 0.05)

Remodelace živé kosti indukované dynamickým zatížením a dodáním léčiv – Numerické modelování a klinická terapie

The bone remodelling process is described by five ordinary differential equations for the concentrations of five relevant chemical components - mononuclear cells, old bone, osteoblast activators, osteoid and new bone. Driving force of bone remodelling process is a dynamic loading which strongly influences the rate of chemical reactions. The evolution from the homogeneous density distribution to the cancellous bone formation is shown. An influence of a dynamic mechanical loading and osteoprotegerin concentration is demonstrated. Bone deformations were calculated by commercial code ANSYS

Biologická aplikace nevratné termodynamiky - kardiovaskulární systém člověka a remodelace kostí

The paper deals with irreversible thermodynamics of open systems which offers a new concept for description of real material objects including the living systems. The biological application of this theory is demonstrated by the numerical hemodynamical model of the human cardiovascular system and by the biomechanical model of the bone remodeling

The connection between the principle of the least action and the thermodynamic condition of stability

The extended principle is formulated for a material point (M.P.) X, which has nonzero mass, temperature, and trajectory x(X,t). The Lagrangian of this variation principle is equal to the kinetic energy from which, the internal energy of the material point (which depends on the entropy) and the additional energy caused by the frictional force are subtracted. The relation between the inertial force and the entropy gradient is found and the gravitational force is completely replaced by the entropy gradient. Thanks to the mentioned properties of the total enthalpy, the Thermodynamic criterion of stability of the state of M.P., is formulated

Využití nevratné termodynamiky k popisu tekutin a pevných látek

The II. Law of Thermodynamics is interpreted as an evolution law of all material systems, which are in interaction with their surroundings. The most important quantity is the entropy, which is defined by the balance law of entropy. The production of the entropy gives information about the processes into the systems and the convexity of the entropy informs us about the stability of the system states. Under the appropriate outer conditions the fluctuations can to drive the systems to an instability. This lecture is devoted to the fluid flow stability and life assessment of thermoviscoelestic solids components