Репозиторий Университета

© The Author(s) 2019. Responses of five rotary blood pumps, namely HeartAssist 5, HeartMate II, HeartWare, Sputnik 1, and Sputnik 2, were extensively assessed in six test cases using a mathematical model of the cardiovascular system. Data for the rotary pumps were derived from pressure–flow curves reported in the literature. The test cases were chosen to attempt to cover most common clinical conditions, such as partial or full support or transitions between different levels of ventricular support. The investigated parameters are collected in a table and presented in figures, such as pressure–volume loops, H-Q curves, pump flow, and aortic pressure waveforms. HeartAssist, Sputnik 1, and Sputnik 2 pumps provide comparable level of aortic pressure, pump flow pulsatility PI(QP), and aortic pressure pulsatility PI(AoP) due to the similarity of pressure–flow characteristic curves of these pumps. HeartMate II provides a minimal backflow among other investigated rotary blood pumps due to the maximum pressure head at zero flow. HeartWare provides minimal pulsation of flow, which is confirmed by a flow range from −2 to 7 L/min in case 1. At the same time, the greatest degree of unloading was demonstrated by the HeartWare due to the flatness of the pressure–flow curve shape. The conclusions were made based on the obtained results, including the influence of pressure–flow curve shape on the pump performance and occurrences of adverse events, such as backflow or suction. For example, the increase of the pressure head at zero flow decreases the likelihood of backflow through the pump, and with it, increasing the flow under minimal pressure head increases the likelihood of suction.

© 2018 Elsevier Ltd The variation of blood flow waveform in the internal carotid artery (ICA) with age is a well-documented hemodynamic phenomenon, but little is known about how such variation affects the characteristics of blood flow in aneurysms present in the region. In the study, hemodynamic simulations were conducted for 26 ICA aneurysms, with flow waveforms measured in the ICAs of young and older adults being used respectively to set the inflow boundary conditions. Obtained results showed that replacing the young-adult flow waveform with the older-adult one led to little changes (<10%) in simulated time-averaged wall shear stress (WSS), transient maximum WSS, relative residence time and trans-aneurysm pressure loss coefficient, but resulted in a marked increase (32.36 ± 17.24%) in oscillatory shear index (OSI). Frequency-domain wave analysis revealed that the progressive enhancement of low-frequency harmonics dominated the observed flow waveform variation with age and was a major factor contributing to the increase in OSI. Cross-sectional comparisons among the aneurysms further revealed that the degree of increase in OSI correlated positively with some specific morphological features of aneurysm, such as aspect ratio and size ratio. In summary, the study demonstrates that the variation in flow waveform with age augments the oscillation of WSS in ICA aneurysms, which underlies the importance of setting patient-specific boundary conditions in hemodynamic studies on cerebral aneurysms, especially those involving long-term patient follow-up or cross-sectional comparison among patients of different ages.

AIM: To study the state of cerebral hemodynamics and platelet hemostasis in patients with carotid stenosis (CS). MATERIAL AND METHODS: The prospective study included 123 patients with atherosclerotic CS. The 1st group included 53 patients (mean age 52±12.5 yrs) who underwent carotid endarterectomy (CEA); the 2nd group - 70 patients who were treated conservatively (mean age 58.5±15.9 yrs). The state of blood flow through the main arteries of the head (Doppler flowmetry), platelet aggregation induced by adrenaline, the frequency of acute cardiovascular events that occurred during 12 months were evaluated. RESULTS AND CONCLUSION: The severity of neurological deficits and cognitive impairment increased with increasing of the degree of CS. CEA leads to an improvement of cerebral hemodynamics and stabilization of cognitive functions. The adverse course of the disease occurred in 23.6% of patients (stroke/heart attack during the year in 5.7%, progression of cerebral ischemia in 20%, restenosis within 5 years after CEA in 15%). Hyperaggregation of platelets induced by ADP and epinephrine and decreased aggregation of platelets induced by collagen in patients receiving ASA were identified in 53% of the operated and in 60% of non-operated patients. The use of combined antiplatelet therapy normalize the platelet hemostasis and reduce the frequency of acute cardiovascular events.