Narrow Results

The phase opposition of velocity waveforms between coronary arteries (predominantly diastolic) and veins (systolic) is the most prominent characteristic of coronary hemodynamics. The phase opposition indicates the importance of intramyocardial capacitance vessels, as a determinant of phasic coronary arterial and venous flows. To investigate the functional characteristics of the intramyocardial capacitance vessels and its physiological significance, we analyzed the change in venous flow following changes in coronary arterial inflow. It was shown that during diastole the intramyocardial capacitance vessels have two functional components, unstressed volume and ordinary capacitance. Unstressed volume is defined as the volume of blood in a vessel at zero transmural pressure, and it was ~5% of the volume of the myocardium. The systolic coronary venous outflow showed a significant, positive correlation with the total displaceable blood volume stored in the intramyocardial unstressed volume and ordinary capacitance. When the unstressed volume was saturated, the coronary inflow was decreased significantly, compared with that for the unsaturated condition. Thus, the increase in intramyocardial blood volume decreases the coronary arterial inflow, whereas it enhances coronary venous outflow. The latter is an interesting analogy to the Starling's law of the heart.

Vortices in flow past a heart valve, in streams and behind an arrow were realized, sketched and discussed by Leonardo da Vinci. The forced resonance and collapse of the Tacoma Narrows Bridge under 64 km/h. wind in 1940 and the Kármán vortex street are classic examples of dynamic interaction between fluid flow and solid motion. There are similar and dissimilar characteristics of vortices between biological and physical flow processes. They can be analyzed by numerical solutions of the Navier–Stokes equations with moving boundaries. One approach is to transform the time-dependent domain to a fixed domain with the geometric, kinematic and dynamic parameters as forcing functions in the Navier–Stokes equations.

Background: The fractional flow reserve (FFR) is the gold standard used to diagnose whether coronary stenosis triggers myocardial ischemia. Myocardial ischemia is not only related to the degree of coronary artery disease but also to hemodynamic parameters such as mean arterial pressure, flow, and so on. This paper will explore the effects of hemodynamic parameters on FFR. Methods: Construct an ideal vascular model of moderately stenosis lesions (40–70%) with different hemodynamic environments. A pressure waveform was set as the inlet boundary, a microcirculation resistance in the hyperemia state was set as the outlet boundary, and different hemodynamic environments were constructed by changing the mean arterial pressure and flow at rest. The microcirculation resistance in the resting state was determined by the mean arterial pressure and flow, and the microcirculation resistance in the hyperemia state was 0.24 times than in the resting state. Results:Flow at rest was found to have the greatest impact on FFR, followed by arterial pressure. Both a decrease in flow and an increase in mean arterial pressure caused an increase in the FFR value. Conclusion:Based on the degree of stenosis of the diseased blood vessel, systolic pressure, diastolic blood pressure, and blood flow through the diseased blood vessel in the resting state, a preliminary judgment can be directly made as to whether the stenosis causes myocardial ischemia.